US20030168132A1 - Method for measuring particle size of inclusion in metal by emission spectrum intensity of element constituting inclusion in metal, and method for forming particle size distribution of inclusion in metal, and apparatus for executing that method - Google Patents

Method for measuring particle size of inclusion in metal by emission spectrum intensity of element constituting inclusion in metal, and method for forming particle size distribution of inclusion in metal, and apparatus for executing that method Download PDF

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US20030168132A1
US20030168132A1 US10/258,906 US25890603A US2003168132A1 US 20030168132 A1 US20030168132 A1 US 20030168132A1 US 25890603 A US25890603 A US 25890603A US 2003168132 A1 US2003168132 A1 US 2003168132A1
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particle size
intensity
intermetallic
intermetallic inclusions
constituent element
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Wataru Nagasawa
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NSK Ltd
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NSK Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/66—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/02—Investigating particle size or size distribution
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/10—Investigating individual particles
    • G01N15/14—Optical investigation techniques, e.g. flow cytometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/02—Investigating particle size or size distribution
    • G01N15/0205—Investigating particle size or size distribution by optical means
    • G01N15/0227—Investigating particle size or size distribution by optical means using imaging; using holography

Definitions

  • This invention relates to a method of determining particle sizes of non-metallic inclusions dispersed in metal materials (hereinafter referred to as an “intermetallic inclusions”) based on emission spectrum intensities of constituent elements of the intermetallic inclusions, and a method of generating particle size distributions of the intermetallic inclusions, as well as to apparatuses for performing the methods, and more particularly to a method of determining particle sizes of intermetallic inclusions based on emission spectrum intensities of constituent elements of the intermetallic inclusions by using an emission spectral analysis method, and a method of generating particle size distributions of intermetallic inclusions, as well as to apparatuses for performing the methods.
  • a steel material contains various kinds of intermetallic inclusions dispersed therein.
  • the compositions as well as the particle sizes of the compositions and the particle size distribution of these intermetallic inclusions seriously affect the quality of the steel material, particularly the pureness of roller bearings when the steel material is used as a material for the roller bearings. Therefore, to maintain the pureness of the steel material, it is important to identify the composition of each intermetallic inclusion in the steel material and determine the particle size distribution of intermetallic inclusions existing in a predetermined area of the steel material, i.e. to determine or measure the number of intermetallic inclusions existing in the steel material for each predetermined particle size.
  • the method using emission spectral analysis identifies respective compositions of intermetallic inclusions by separating an emission spectrum emitted from intermetallic inclusions contained in a steel material which was subjected to spark discharge, into emission spectra specific to respective elements, and therefore, the method is advantageous in that the composition of each intermetallic inclusion can be identified speedily, and therefore, a number of methods using emission spectral analysis have been disclosed e.g. in “Iron and Steel vol. 73 (1987) S696, S670”, “CAMP-IsIJ vol. 7 (1994) 1292, 1293”, and Japanese Laid-Open Patent Publications (Kokai) Nos. 4-238250 and 9-43150.
  • a method described in Japanese Laid-Open Patent Publication (Kokai) No. 4-238250 measures, in time sequence, ones of emission spectra obtained by spark discharge which correspond to zero to several hundreds of pulses corresponding to an initial stage of the spark discharge, and then determines the number of intermetallic inclusions and the compositions and contents of intermetallic inclusions, based on ones of the measured emission spectra falling within a predetermined intensity range, using predetermined equations.
  • the method described in Japanese Laid-Open Patent Publication (Kokai) No. 4-238250 separates emission spectra emitted from intermetallic inclusions contained in a steel material subjected to a spark discharge generated under discharge conditions adapted to the steel material, into emission spectra specific to respective elements, identifies the composition of the intermetallic inclusions based on the wavelength and/or intensity of the obtained emission spectra inherent to the respective elements, and then determines the concentration of each constituent element and the particle sizes of the intermetallic inclusions.
  • the disclosed method carries out extrapolation of a calibration relationship in a trace concentration region. The extrapolation makes it difficult for the disclosed method to correctly determine the particle sizes and the particle size distribution.
  • a calibration curve concerning concentrations of a specific metal element of the intermetallic inclusions which is obtained from a trace amount of a master, and hence when it is necessary to carry out the identification even in a high concentration region where the concentration of the metal element of the intermetallic inclusions is high, as in the case of determining particle sizes and a particle size distribution of the intermetallic inclusions, there is no choice but to estimate the calibration relationship up to the high concentration region by extrapolation used in the low concentration region, which makes the calibration relationship inaccurate. For this reason, the use of an alloy as a master which has a high concentration of a certain metal element falling within a known range in intermetallic inclusions, e.g.
  • an Al-based alloy as the master in the case of Al being a constituent element of intermetallic inclusions, may be contemplated so as to obtain a calibration relationship in a region where the concentration of the metal element in intermetallic inclusions is high.
  • the background of the Al-based alloy is not iron (Fe)
  • Fe iron
  • due to existence of a high emission spectrum intensity of an element, such as Mg, whose emission wavelength is close to that of Al it is difficult to correctly identify the concentration of Al.
  • the manner of preparing test samples is simple, the determination can be performed easily, and a passably accurate average particle size can be determined (see FIG. 4) so long as an appropriate averaging method and an appropriate statistical method are used, the average particle size obtained by the method may be estimated as a smaller apparent particle size than the real particle size.
  • the real particle size obtained by calculating a spherical diameter from the volume of an intermetallic inclusion particle
  • the average particle size of the Al 2 O 3 or other intermetallic inclusions, obtained through the image analysis is estimated to be smaller than the real particle size as described above. Since the correlation between the average particle size thus estimated to be smaller and the real particle size cannot be clearly determined, the relationship between the average particle size estimated to be smaller and the rolling life may not be accurately determined.
  • Methods for directly determining the particle size of intermetallic inclusions include a method in which intermetallic inclusions e.g. of Al 2 O 3 are extracted from a steel material providing test samples, by an electron beam elution method or a chemical extraction method, into grains.
  • intermetallic inclusions e.g. of Al 2 O 3
  • a particle size-determining method as recited in claim 1 is characterized by comprising the steps of determining a particle size of the intermetallic inclusions, which is known, in a predetermined area of a reference sample, determining an intensity of emission spectra emitted from the constituent element of the intermetallic inclusions, from a relationship thereof to an intensity of emission spectra from spark discharge spots within the predetermined area, through emission spectral analysis of the reference sample, and forming an inclusion particle size-intensity calibration curve representative of the relationship between the particle size of the intermetallic inclusions and the emission spectrum intensity of the constituent element of the intermetallic inclusions.
  • the particle size of the intermetallic inclusions, which is known, in the predetermined area of the reference sample is determined through surface analysis by an electron probe microanalyzer.
  • a particle size-determining method as recited in claim 3 is characterized by comprising the steps of determining an intensity of emission spectra emitted from a principle component having an already known concentration and contained in a reference sample having an already known concentration in spark discharge spots within a predetermined area of the reference sample, through emission spectral analysis of the reference sample, forming a principle component known concentration-intensity calibration curve representative of the relationship between the emission spectrum intensity of the principle component having an already known concentration and the known concentration of the principle component, determining an intensity of emission spectra emitted from a principle component contained in a real steel material-reference sample in spark discharge spots within a predetermined area of the real steel material-reference sample, and an intensity of emission spectra emitted from a constituent element of intermetallic inclusions contained in the real steel material-reference sample, through emission spectral analysis of the real steel material-reference sample, calculating a concentration of the principle component contained in the real steel material-reference sample from the emission
  • the particle size-determining method comprising the steps of calculating a base element evaporation volume indicative of a volume of the evaporated base element, from the base element evaporation amount based on a density of the base element, and calculating, from the base element evaporation volume, a particle size of the intermetallic inclusions as a diameter thereof corresponding to the base element evaporation volume, based on a formula of calculating a spherical volume, determining a known concentration of the principle component from the emission spectrum intensity of the base element, based on the principle component known concentration-intensity calibration curve, calculating a concentration of the constituent element of the intermetallic inclusions based on the determined known concentration of the principle component, determining an intensity of emission spectra of the constituent element of the intermetallic inclusions from the calculated concentration of the constituent element of the intermetallic inclusion, based on the real steel material-contained intermetallic inclusion constituent element concentration-intensity calibration curve, and forming an intermetallic inclusion particle
  • a particle size distribution-generating method as recited in claim 5 is characterized by comprising the steps of executing a data sorting process for counting a number of data items of emission spectra of a constituent element of the intermetallic inclusions in a test sample, and generating a particle size distribution based on the counted number of the data items and the particle size of the intermetallic inclusions in the test sample, which have been determined by any of the particle size-determining methods described above.
  • the data items of emission spectra of the constituent element of the intermetallic inclusions in the test sample are rearranged in order of intensity, and then the number of the rearranged data items is counted.
  • the particle size distribution-generating method as recited in claim 8 further comprising the step of determining an intensity of emission spectra emitted from a principle component contained in the test sample, and in the data sorting process, the data items of intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample to be rearranged in order of intensity are extracted based on a result of comparison between the intensity of emission spectra emitted from the principle component contained in the test sample and the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample.
  • the particle size distribution-generating method further comprising the steps of forming an intensity correction curve representative of the relationship between a number of times of generation of spark discharge for emission spectral analysis and an amount of attenuation of an intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample after carrying out the spark discharge, and correcting the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample according to the number of times of generation of spark discharge for emission spectral analysis, based on the generated intensity correction curve.
  • a kind of the constituent element of the intermetallic inclusions contained in the test sample is identified based on a result of comparison between the intensity of emission spectra emitted from the principle component contained in the test sample and the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample.
  • a particle size-determining apparatus as recited in claim 11 is characterized by comprising acquiring means for acquiring a particle size of the intermetallic inclusions, which is known, in a predetermined area of a reference sample, acquiring means for acquiring an intensity of emission spectra emitted from the constituent element of the intermetallic inclusions, from a relationship thereof to an intensity of emission spectra from spark discharge spots within the predetermined area, through emission spectral analysis of the reference sample, and forming means for forming an inclusion particle size-intensity calibration curve representative of the relationship between the particle size of the intermetallic inclusions and the emission spectrum intensity of the constituent element of the intermetallic inclusions.
  • the particle size-determining apparatus comprises acquiring means for acquiring the particle size of the intermetallic inclusions, which is known, in the predetermined area of the reference sample through surface analysis by an electron probe microanalyzer.
  • a particle size-determining apparatus as recited in claim 13 is characterized by comprising acquiring means for acquiring an intensity of emission spectra emitted from a principle component having an already known concentration and contained in a reference sample having an already known concentration in spark discharge spots within a predetermined area of the reference sample, through emission spectral analysis of the reference sample, forming means for forming a principle component known concentration-intensity calibration curve representative of the relationship between the emission spectrum intensity of the principle component having an already known concentration and the known concentration of the principle component, acquiring means for acquiring an intensity of emission spectra emitted from a principle component contained in a real steel material-reference sample in spark discharge spots within a predetermined area of the real steel material-reference sample, and an intensity of emission spectra emitted from a constituent element of intermetallic inclusions contained in the real steel material-reference sample, through emission spectral analysis of the real steel material-reference sample, calculating means for calculating a concentration of the principle component
  • the particle size-determining apparatus comprises calculating means for calculating a base element evaporation volume indicative of a volume of the evaporated base element, from the base element evaporation amount based on a density of the base element, and calculating, from the base element evaporation volume, a particle size of the intermetallic inclusions as a diameter thereof corresponding to the base element evaporation volume, based on a formula of calculating a spherical volume, acquiring means for acquiring a known concentration of the principle component from the emission spectrum intensity of the base element, based on the principle component known concentration-intensity calibration curve, calculating means for calculating a concentration of the constituent element of the intermetallic inclusions based on the determined known concentration of the principle component, acquiring means for acquiring an intensity of emission spectra of the constituent element of the intermetallic inclusions from the calculated concentration of the constituent element of the intermetallic inclusion, based on the real steel material-contained intermetallic inclusion constituent element concentration-intensity
  • a particle size distribution-generating apparatus as recited in claim 15 is characterized by comprising data sorting means for executing a data sorting process for counting a number of data items of emission spectra of a constituent element of the intermetallic inclusions in a test sample, and generating means for generating a particle size distribution based on the counted number of the data items and the particle size of the intermetallic inclusions in the test sample, which have been determined by the particle size-determining apparatuses described above.
  • data sorting means rearranges the data items of emission spectra of the constituent element of the intermetallic inclusions in the test sample counts the number of the rearranged data items.
  • the data sorting means determines whether or not an emission spectrum intensity of the constituent element of the intermetallic inclusions in the test sample is larger than a threshold value, and then extracts data items of intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample to be rearranged in order of intensity, based on a result of the determination.
  • the particle size distribution-generating apparatus further comprises acquiring means for acquiring an intensity of emission spectra emitted from a principle component contained in the test sample, and the data sorting means extracts the data items of intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample to be rearranged in order of intensity, based on a result of comparison between the intensity of emission spectra emitted from the principle component contained in the test sample and the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample.
  • the particle size distribution-generating apparatus further comprises forming means for forming an intensity correction curve representative of the relationship between a number of times of generation of spark discharge for emission spectral analysis and an amount of attenuation of an intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample after carrying out the spark discharge, and correcting means for correcting the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample according to the number of times of generation of spark discharge for emission spectral analysis, based on the generated intensity correction curve.
  • the particle size distribution-generating apparatus comprises identifying means for identifying a kind of the constituent element of the intermetallic inclusions contained in the test sample, based on a result of comparison between the intensity of emission spectra emitted from the principle component contained in the test sample and the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample.
  • FIG. 1 is a diagram schematically showing an emission spectrometer for performing a particle size-determining and particle size distribution-generating method according to a first embodiment of the present invention
  • FIG. 2 is a flowchart of a particle size-determining and particle size distribution-generating process executed according to the particle size-determining and particle size distribution-generating method according to the first embodiment
  • FIG. 3 is a flowchart of a calibration curve A-forming process, which is executed in a step S 201 in FIG. 2, for forming a calibration curve A representative of the relationship between the Al 2 O 3 particle size and the emission spectrum intensity of Al;
  • FIG. 4 is a view schematically illustrating a surface analysis result image of Al existing in Al 2 O 3 ;
  • FIG. 5 is a diagram illustrating the calibration curve A representative of the relationship between the Al 2 O 3 particle size and the emission spectrum intensity of Al, which is formed in a step S 308 in FIG. 3;
  • FIG. 6 is a flowchart of a particle size distribution-generating process which is executed in a step S 202 in FIG. 2;
  • FIGS. 7A to 7 E are diagrams illustrating distributions of data items of emission spectrum intensities of Fe, O, Al, Ca and C, which are arranged in time sequence, for comparison performed in a step S 605 in FIG. 6;
  • FIG. 8 is a flowchart of a data sorting process which is executed in a step S 606 in FIG. 6;
  • FIG. 9 is a continued part of the flowchart of the data sorting process which is executed in the step S 606 in FIG. 6;
  • FIG. 10 is a still continued part of the flowchart of the data sorting process which is executed in the step S 606 in FIG. 6;
  • FIG. 11 is a flowchart of a data sorting process which is executed according to a variation of the particle size-determining and particle size distribution-generating method according to the first embodiment
  • FIG. 12 is a flowchart of a particle size-determining and particle size distribution-generating process which is executed according to a particle size-determining and particle size distribution-generating method according to a second embodiment of the present invention
  • FIG. 13 is a flowchart of a calibration curves B, C-forming process which is executed in a step S 1201 in FIG. 12 for forming a calibration curve B representative of the relationship between the Fe emission spectrum intensity and the Fe concentration and then forming a calibration curve C representative of the relationship between the Al emission spectrum intensity and the Al concentration based on the calibration curve B;
  • FIG. 14 is a diagram illustrating the calibration curve B representative of the relationship between the Fe emission spectrum intensity and the Fe concentration, which is formed in the step S 1201 in FIG. 12;
  • FIG. 15 is a cross-sectional view taken on a section orthogonal to the axis of a steel material for actual use, for example, from which a real steel master is cut out in a step S 1306 in the FIG. 13;
  • FIG. 16 is a flowchart of a calibration curve D-forming process for forming a calibration curve D concerning the Fe emission spectrum intensity and the Fe evaporation loss in a step S 1202 in FIG. 12;
  • FIG. 17 is a view useful for explaining a method of determining a particle size of an intermetallic inclusion in a step S 1605 in FIG. 15;
  • FIG. 18 is a diagram illustrating a calibration curve D representative of the relationship between the Fe evaporation amount and the Fe emission spectrum intensity, which is formed in the step S 1202 in FIG. 12;
  • FIG. 19 is a flowchart of a calibration curve E-forming process which is executed in a step S 1203 in FIG. 12 for forming a calibration curve E representative of the relationship between the Al emission spectrum intensity and the Al particle size;
  • FIG. 20 is a flowchart of a particle size distribution-generating process which is executed in a step S 1204 in FIG. 12;
  • FIG. 21 is a diagram illustrating the calibration curve A representative of the relationship between the Al 2 O 3 particle size and the Al emission spectrum intensity, which is formed in a step S 1907 in FIG. 19;
  • FIG. 22 is a flowchart of a particle size-determining and particle size distribution-generating process according to a third embodiment of the present invention.
  • FIG. 23 is a flowchart of an intensity correction curve-forming process which is executed in a step S 2201 in FIG. 22;
  • FIG. 24 is a diagram illustrating an intensity correction curve which is formed in the step S 2201 in FIG. 22;
  • FIG. 25 is a flowchart of a particle size distribution-generating process which is executed in a step S 2202 in FIG. 22;
  • FIGS. 26A and 26B are diagrams useful in comparison between an Al 2 O 3 particle size distribution (a) generated by execution of the FIG. 2 process and an Al 2 O 3 particle size distribution (b) generated by an EPMA; and
  • FIGS. 27A and 27B are diagrams useful in comparison between the Al 2 O 3 particle size distribution (a) generated by execution of the FIG. 12 process and an Al 2 O 3 particle size distribution (b) generated by the image analysis method.
  • a particle size-determining and particle size distribution-generating method according to a first embodiment of the present invention will now be described in detail with reference to the drawings.
  • the particle size-determining and particle size distribution-generating method of the first embodiment is carried out by an emission spectrometer shown in FIG. 1, described hereinbelow, in generating a particle size distribution of intermetallic inclusions contained in a test sample cut out from a steel material.
  • FIG. 1 is a diagram schematically showing the arrangement of the emission spectrometer for performing the particle size-determining and particle size distribution-generating method according to the first embodiment.
  • the emission spectrometer 100 is comprised of a light-emitting section 101 , a light-emitting stand 102 , a spectral section 103 , a photometric section 104 , an interface 105 , a data processing section 106 , and a terminal unit 107 .
  • the light-emitting section 101 is provided with a counter electrode, not shown, while the light emitting stand 102 contains a test sample or a master (reference sample) serving as an electrode.
  • the spectral section 103 is comprised of a condensing lens 108 , a light shielding plate 111 formed with an entrance slit 109 and a plurality of exit slits 110 , a concave diffraction grating 112 , a plurality of photomultipliers 113 , and an oil rotary pump 114 .
  • the terminal unit 107 includes a CRT, a printer, and a keyboard.
  • the light emitting stand 102 is connected to the interface 105 via the light-emitting section 101 , and the photomultipliers 113 are connected to the interface 105 via the photometric section 104 .
  • the interface 105 is connected to the terminal unit 107 via the data processing section 106 .
  • the light-emitting section 101 is arranged at a location where the counter electrode can generate a spark discharge on the test sample or the master.
  • the light emitting stand 102 is arranged on an optical axis passing through the condensing lens 108 , the entrance slit 109 , and the concave diffraction grating 112 , and at the same time on a surface of the spectral section 103 .
  • the exit slits 110 are arranged on optical beams rotated about the concave diffraction grating 112 through angles of diffraction specific to a plurality of elements, respectively, from the optical axis passing through the condensing lens 108 , the entrance slit 109 , and the concave diffraction grating 112 , and at the same time on the light shielding plate 111 .
  • the photomultipliers 113 are positioned on the optical axes of the respective optical beams.
  • At least a space between the light-emitting section 101 and the light emitting stand 102 is filled with an inert rare gas (e.g. argon gas).
  • an inert rare gas e.g. argon gas
  • the counter electrode of the light-emitting section 101 generates a spark discharge on the test sample or the master which is held in the light emitting stand 102 , and the test sample or the master which is subjected to the spark discharge emits light of emission spectra (emission spectra emitted respectively by iron (Fe) or other main constituents of the test sample or the master (hereinafter referred to as “ground”)) and intermetallic inclusions) containing information on a plurality of elements.
  • the condensing lens 108 converges the emitted light of emission spectra and irradiates the concave diffraction grating 112 with the converged light via the entrance slit 109 .
  • the concave diffraction grating 112 separates the emitted light of emission spectra into emission spectra specific to the respective elements by utilizing the respective angles of diffraction specific thereto, and the separated emission spectra enter the photomultipliers 113 via the respective exit slits 110 .
  • the separated beams of the emission spectra specific to the respective elements contain respective pieces of optical information specific to the elements.
  • the photomultipliers 113 each detect the incoming emission spectrum, convert the intensity of the detected emission spectrum to an electric current value and transmit the converted current value to the photometric section 104 .
  • the photometric section 104 converts the received current value to a digital value, and then transmits the converted digital value to the data processing section 106 via the interface 105 .
  • the light-emitting section 101 and the light emitting stand 102 transmits data of the number of times and timing of generation of spark discharge and data of positions on the surface of the test sample or the master which were subjected to spark discharge to the data processing section 106 via the interface 105 .
  • the data processing section 106 carries out processing including identification of the composition of each intermetallic inclusion, based on the received digital values and so forth.
  • the CRT and a print printed by the printer display and indicates the result of determination of the particle size distribution of intermetallic inclusions.
  • FIG. 2 is a flowchart of the particle size-determining and particle size distribution-generating process executed by the particle size-determining and particle size distribution-generating method of the first embodiment.
  • a calibration curve A-forming process for forming a calibration curve A is executed (step S 201 ), and then a particle size distribution-generating process, described hereinafter with reference to FIG. 6, is executed (step S 202 ), followed by terminating the process.
  • FIG. 3 is a flowchart of the calibration curve A-forming process executed in the step S 201 in FIG. 2, for forming the calibration curve A representative of the relationship between the Al 2 O 3 particle size and the emission spectrum intensity of Al.
  • the calibration curve A-forming process is executed by the emission spectrometer 100 at least once before the particle size distribution-generating process is repeatedly carried out on intermetallic inclusions in the test sample by the emission spectrometer 100 .
  • steel materials of SUJ2 high-carbon chromium bearing steel, Type 2 containing Al 2 O 3 , for example, having a particle size approximately equal to 4 to 18 ⁇ m, which is a normal range of particle sizes of Al 2 O 3 (alumina) contained in the test sample, are prepared, and masters having a cylindrical shape with a diameter of ⁇ 40 mm are cut out from the steel materials.
  • an area e.g. of ⁇ 5 mm is arbitrarily set at an arbitrary location on the surface of the master, and the location of the area is determined.
  • the area is scanned by the EPMA for surface analysis thereof, whereby, when the intermetallic inclusion concerned is Al 2 O 3 , the location of Al is determined by the surface analysis, and then the particle size of Al is determined by a method of determining an average particle size of the intermetallic inclusion from an image showing the location of Al, as described hereinbelow with reference to FIG. 4 (step S 302 ).
  • the intermetallic inclusion concerned is Al 2 O 3
  • Al is employed as an element for identifying the intermetallic inclusion.
  • Ca is employed as an identifying element for CaO (calsia), Mg for MgO (magnesia), Si for SiO 2 , Ca or S for CaS, Ti or N for TiN, or Mn or S for MnS, and surface analysis using such an identifying element provides a surface analysis result image concerning the metal element of a corresponding intermetallic inclusion, thereby similarly making it possible to determine the average particle size thereof.
  • FIG. 4 schematically illustrates a surface analysis result image of Al in Al 2 O 3 .
  • the EPMA determines a major diameter d max of an intermetallic inclusion 400 and a minor diameter d min of the same, and based on these sizes, an average diameter d ave is calculated as the particle size of the intermetallic inclusion 400 by using the following equation (1):
  • step S 303 data of the location and particle size of the intermetallic inclusion determined by surface analysis and the identified constituent element of the intermetallic inclusion are input to the data processing section 106 (step S 303 ), and the data processing section 106 stores the input data in a memory, not shown.
  • the counter electrode of the light-emitting section 101 generates spark discharge e.g. one hundred times at a surface area (set e.g. to ⁇ 5 mm) of the surface of the master which is the same area that was operated by the EPMA (step S 305 ).
  • the master subjected to the spark discharge produces emission spectra containing information on a plurality of elements.
  • the intermetallic inclusion in the surface of the master has a dielectric property, and hence at this time, the spark discharge is selectively guided to the intermetallic inclusion in the surface of the master by the dielectric property (electrification) thereof. Accordingly, the emission spectra generated by the master are emitted from respective discharge spots (e.g. ⁇ 30 ⁇ m) thereof containing the intermetallic inclusion.
  • emission spectrum intensities of Al arranged in order in which the intensity of Al decreases correspond respectively to average particle sizes of Al 2 O 3 which are obtained by the above-mentioned surface analysis by the EPMA and arranged in order in which the size of Al 2 O 3 decreases.
  • the data of the emission spectrum intensities and the average particle sizes obtained earlier by the EPMA are input to the memory of the data processing section 106 , and then these data are processed according to the intensity of Al by the data processing section 106 , whereby the calibration curve A, referred to hereinafter in a step S 308 and shown in FIG. 5, can be obtained.
  • the obtained calibration curve A is stored in the memory of the data processing section 106 .
  • an area (emission spot) within the surface (the aforementioned area of ⁇ 5 mm) of the master, on which spark discharge is effected once, is a circle of ⁇ 30 ⁇ m (the size is always held constant), and since this emission spot has the diameter of ⁇ 30 ⁇ m which is larger than the average particle size d ave of general intermetallic inclusions, the emission spot can always contain at least one intermetallic inclusion therein, so that all the respective emission spectrum intensities of elements constituting intermetallic inclusions in the master can be obtained. This makes it possible to properly associate the intermetallic inclusions from which the emission spectra were obtained with the intermetallic inclusions having the respective average particle sizes d ave , which were obtained by the EPMA method.
  • each of emission spectra emitted by the master is separated into emission spectra specific to the respective elements by the concave diffraction grating 112 , and the separated emission spectra enter respective ones of the photomultipliers 113 via the corresponding exit slits 110 (step S 306 ).
  • Each photomultiplier 113 detects the incoming emission spectrum, converts the intensity of the detected emission spectrum to an electric current value, and transmits the current value obtained by the conversion to the photometric section 104 .
  • the photometric section 104 converts each of the received current values to a digital value, and then transmits the digital values obtained by the conversion to the data processing section 106 via the interface 105 (step S 307 ).
  • the light emitting stand 102 transmits data of the locations of emission spots in the area of ⁇ 5 mm on the surface of the master, i.e. the locations of intermetallic inclusions to the data processing section 106 via the interface 105 .
  • the data of the respective intensities of emission spectra of the elements constituting each of the intermetallic inclusions and the data of the locations of the intermetallic inclusions are transmitted to the data processing section 106 , and stored in the memory of the same.
  • the data processing section 106 Based on the data of the locations and particle sizes of the intermetallic inclusions and the data of the constituent elements of the intermetallic inclusions and the emission spectrum intensities of the constituent elements, which are stored in the memory, the data processing section 106 generates the FIG. 5 calibration curve A, described hereinbelow, which represents the relationship between the emission spectrum intensity and particle size of one of the elements constituting the intermetallic inclusions as described hereinabove (step S 308 ). Further, the data processing section 106 stores the generated calibration curve A in the memory (step S 309 ), followed by terminating the process.
  • FIG. 5 is a diagram illustrating the calibration curve A formed in the step S 308 in FIG. 3.
  • the calibration curve A indicates the relationship between the Al 2 O 3 particle size and the emission spectrum intensity of Al.
  • the ordinate represents Al 2 O 3 particle sizes determined by the surface analysis by the EPMA, while the abscissa represents the emission spectrum intensities of Al contained in Al 2 O 3 , which correspond to the respective Al 2 O 3 particle sizes.
  • the data of the particle sizes of the intermetallic inclusions determined by the surface analysis by the EPMA method and the data of the emission spectrum intensities of the constituent element existing in the intermetallic inclusions are related to each other via the data of the locations and the data on the constituent element of the intermetallic inclusions.
  • the data of the particle sizes of intermetallic inclusions are represented by the ordinate, and the data of the emission spectrum intensities of one of the elements forming the intermetallic inclusions are represented by the abscissa.
  • step S 307 if the determination by surface analysis is carried out on Al by using masters containing Al 2 O 3 , it is possible to obtain a calibration curve concerning Al 2 O 3 , and if the determination by surface analysis is carried out on Ca by using masters containing CaO, it is possible to obtain a calibration curve concerning CaO.
  • FIG. 5 shows the calibration curve concerning Al 2 O 3 , which shows that the particle size of Al 2 O 3 is larger as the emission spectrum intensity of Al is higher.
  • the particle sizes of intermetallic inclusions determined by the EPMA method and the emission spectrum intensity of metal elements existing in the same intermetallic inclusions can be associated with each other not only by the above method using correspondence between the size-decreasing order and the intensity-decreasing order, but also by a method using position coordinates of intermetallic inclusions within the ⁇ 5 mm area.
  • the FIG. 5 calibration curve A can be formed by either of these methods.
  • intermetallic inclusions contained in a test sample are not limited to Al 2 O 3 , but calibration curves concerning CaO, MgO, SiO, CaS, TiN, MnS, and so forth can also be formed similarly to the FIG. 5 calibration curve. Therefore, it is preferable to store the calibration curves thus formed as well in the memory of the data processing section 106 .
  • step S 302 since an area of ⁇ 5 mm at an arbitrary location on the surface of a master is scanned by the EPMA (step S 302 ), it is possible to determine particle sizes of intermetallic inclusions contained in emission spots having a diameter of 30 ⁇ m within the ⁇ 5 mm area of the master containing the intermetallic inclusions having particle sizes of 4 to 18 ⁇ m, and based on the determined particle sizes of the intermetallic inclusions, the calibration curve A representative of the relationship between the particle size of the intermetallic inclusions and the emission spectrum intensity of an element constituting the intermetallic inclusions is formed (step S 308 ), so that data of particle sizes in a range of 4 to 18 ⁇ m (i.e. a target particle size range of the test sample, described hereinafter) or in its vicinity indicated by the generated calibration curve A can be made accurate.
  • a target particle size range of the test sample i.e. a target particle size range of the test sample, described hereinafter
  • FIG. 6 is a flowchart of the particle size distribution-generating process which is executed in the step S 202 in FIG. 2.
  • the present process is executed by the emission spectrometer 100 whenever a particle distribution of intermetallic inclusions in a test sample is repeatedly generated after the FIG. 3 process by the emission spectrometer 100 is executed at least once.
  • step S 601 a cylindrical test sample of ⁇ 40 mm cut out from a steel material of SUJ2 is held in the light emitting stand 102 (step S 601 ), and then spark discharge is generated e.g. one thousand times at a measurement area ( ⁇ 5 mm) on the surface of the test sample by the counter electrode of the light-emitting section 101 (step S 602 ).
  • the test sample subjected to spark discharge emits light of emission spectra.
  • the light of emission spectra emitted from the test sample is separated into emission spectra specific to respective elements by the concave diffraction grating 112 , and the separated emission spectra enter respective ones of the photomultipliers 113 via the corresponding exit slits 110 (step S 603 ).
  • the photomultipliers 113 each detect the incoming emission spectrum and convert the intensity of the detected emission spectrum into an electric current value and transmit the current value to the photometric section 104 .
  • the photometric section 104 converts the received current value to a digital value, and then transmits the digital value to the data processing section 106 via the interface 105 (step S 604 ).
  • the light emitting stand 102 transmits data of the location of each emission spot within the measurement area on the surface of the test sample and the number of times of generation of spark discharge to the data processing section 106 via the interface 105 .
  • the data of the respective emission spectrum intensities of elements existing in emission spots, the locations of the emission spots, and the number of times of generation of spark discharge are transmitted to the data processing section 106 , and the data processing section 106 stores the data in its memory.
  • the data processing section 106 arranges the data of the respective emission spectrum intensities of the elements in a time sequence order to generate diagrams as shown in FIGS. 7A to 7 E, described hereinbelow, each illustrating a distribution of the data of the emission spectrum intensities. Further, the data processing section 106 compares data of the respective intensities of the emission spectra of the elements emitted from the same emission spot, to thereby determine whether or not there exist intermetallic inclusions within the emission spot, and when there exist intermetallic inclusions, the data processing section 106 identifies the intermetallic inclusions (step S 605 ).
  • FIGS. 7A to 7 E are diagrams showing data of the respective time-sequential emission spectrum intensity distributions of Fe, O, Al, Ca and C, which are compared in the step S 605 in FIG. 6.
  • FIGS. 7A to 7 E a broken line in each of the diagrams related, respectively, to O, Al, Ca and C indicates a threshold value for use in determining whether or not the corresponding element is solid-solved in a material (matrix).
  • a threshold value for use in determining whether or not the corresponding element is solid-solved in a material (matrix).
  • the data processing section 106 executes a data sorting process described hereinafter with reference to FIGS. 8 to 10 , to rearrange the data of the emission spectrum intensities of an element specific to each of the intermetallic inclusions identified in the step S 605 in intensity-increasing order (step S 606 ).
  • the data processing section 106 deletes data of emission spectrum intensities whose values are smaller than the corresponding threshold value.
  • the emission spectrum intensities of Al are substituted into the data of the rearranged emission spectrum intensities and the calibration curve A representative of the relationship between the Al 2 O 3 particle size and the emission spectrum intensity of Al, which was formed by the FIG. 3 process, whereby the Al 2 O 3 particle sizes are calculated (step S 607 ), and based on the calculated Al 2 O 3 particle sizes and the number of the data, a particle distribution of the intermetallic inclusions is generated.
  • the generated data of the particle size distribution is displayed on the CRT or the printer. According to the FIG.
  • intermetallic inclusions existing in an emission spot on the surface of a test sample is identified based on the data of the respective emission spectrum intensities of elements existing in the emission spot (step S 605 ), and then the particle sizes of the identified intermetallic inclusions are calculated, based on the data of the emission spectrum intensities and the calibration curve A formed by the FIG. 3 process (step S 607 ). This makes it possible to perform quick and accurate determination of the particle sizes and particle size distribution of the intermetallic inclusions.
  • FIGS. 8 to 10 are a flowchart of the data sorting process which is executed in the step S 606 in FIG. 6.
  • the data processing section 106 rearranges data I x (i) of a row I x of emission spectrum intensities specific to a constituent element X as one of the constituent elements of the intermetallic inclusion identified in the step S 605 e.g. in intensity-increasing order, into a row AL x while deleting data items I x (i) whose values are smaller than the threshold value for the constituent element X.
  • a count K indicative of the number of data items I x (i) whose values are determined to be equal to or larger than the threshold value for the constituent element X is calculated by using the following equation (2) (step S 803 ):
  • the fetched data item I x (i) is substituted for a data item A x (K) in a row A x as a set of data items I x (i) which are equal to or larger than the threshold value for the constituent element X (step S 804 ). Further, the count K is regarded as the maximum value of the current count i at the present time and substituted for K max (step S 805 ).
  • step S 806 If the fetched data item I x (i) is determined to be smaller than the threshold value for the constituent element X in the step S 802 , the count ii is incremented by 1 (step S 806 ), followed by the process proceeding to a step S 807 .
  • step S 807 it is determined whether or not the present count i is smaller than the number of times J (1000 times) of generation of spark discharge.
  • step S 807 If the count i is determined to be smaller than the number of times J of generation of spark discharge in the step S 807 , the present count i is incremented by 1 (step S 808 ), followed by the process returning to the step S 802 , whereas if the present count i is determined to be equal to or larger than the number of times J of generation of spark discharge, the process proceeds to a step S 901 (FIG. 9).
  • step S 904 To determine which row data A x is the smaller on the right side of the equation (3), it is determined whether or not ⁇ A x (K) is equal to or smaller than 0 (step S 904 ).
  • step S 904 the data item A x (K+1) in the row A x is substituted for the variable B x (l) (i.e. the value of the variable B x (l) is updated) (step S 909 ), and the variable B x (l) is substituted for the minimum value in the row data AL x (l) in which data items I x (i) are rearranged in value-increasing order with respect to 1 (step S 910 ). Then, e.g.
  • This operation is carried out in order to compare the value of the data item A x (K+1) with the minimum value AL x (l) which has been provisionally selected from the row A x .
  • step S 919 it is determined whether or not the incremented index l is smaller than K max . This step is executed in order to determine whether or not the arithmetic operations for all values of the index l have been completed.
  • step S 919 If the incremented index l is determined to be equal to or larger than K max in the step S 919 , i.e. if arithmetic operations have been completed for all the values of the index l, the process proceeds to a step S 1001 (FIG. 10).
  • arithmetic operations are carried out for determining a frequency C x (l) indicative of a number (m) of data items AL x (l) having the same value in the row AL x of data items AL x (l) which are all equal to or larger than the threshold value for the constituent element X, i.e. for determining the number (m) of intermetallic inclusions exist for each particle size [ ⁇ m].
  • step S 1001 the index l is incremented by 1, and then 1 is substituted for an arbitrary value n in the index l (step S 1002 ). Further, the count m of a counter which calculates the number of intermetallic inclusions which have the same particle size as that of AL x (l) existing in K max is set to 1 (step S 1003 ) Then, ⁇ AL x (l) representative of the difference between the value of the data AL x (l) for the index l in the row AL x and the value of the data item AL x (n) with the arbitrary value n substituted in the index l is calculated by using the following equation (5) (step S 1004 ):
  • step S 1005 it is determined whether or not the calculated ⁇ AL x (l) is equal to 0 (step S 1005 ).
  • step S 1006 the count m representative of the number of the data items AL x (n) having the same value is held at m, and the process proceeds to a step S 1010 .
  • step S 1005 it is determined whether or not the arbitrary value n is equal to 1 (step S 1007 ).
  • step S 1007 If the arbitrary value n is determined to be equal to 1 (the index l is 1, and the calculated difference ⁇ AL x (l) is 0) in the step S 1007 , the data count m is set to 1 (step S 1008 ), whereas if the arbitrary value n is not determined to be equal to 1, the data count m is incremented by 1 (step S 1009 ).
  • step S 1010 the arbitrary value n is incremented by 1, and then it is determined whether or not the arbitrary value n is smaller than the maximum value K max of the index l (step S 1011 ).
  • the process returns to the step S 1004 , wherein the steps S 1004 et seq. are repeatedly executed until the arbitrary value n has covered all the values of the index l.
  • the arbitrary value n is equal to or larger than the maximum value K max of the index l, it means that the arbitrary values n has covered all the values of the index l, and hence the data count m at this time is set to the number C x (1) of the data items AL x (n) (step S 1012 ).
  • the index l is incremented by 1 (step S 1013 ), and this value of the index l is regarded as the present maximum value l max of the index l, and it is determined whether or not the present maximum value l max is smaller than K max (step S 1014 ). If the present maximum value l max is smaller than K max , the process returns to the step S 1002 , whereas if the present maximum value l max is equal to or larger than K max , the present process is terminated.
  • step S 607 if the data items AL x (l), AL x (i) having the same value, which were fetched from the row AL x of the data items AL x (l) each having a value equal to or larger than the threshold value for the constituent element X, are each converted from the emission spectrum intensity of the constituent element X (e.g. Al) to a particle size of the intermetallic inclusion by using FIG. 5, described hereinbefore, or FIG. 21, described hereinafter (step S 607 ), this means that the frequency C x (l) indicative of the number (m) of intermetallic inclusions existing for each particle size [ ⁇ m] is obtained. Therefore, it is possible to display or output a diagram shown in FIG. 26A, described hereinafter, based on the particle sizes [ ⁇ m] and the row data C x (l) representative of frequencies, in the same manner as a diagram shown in FIG. 26B, which is obtained by the EPMA.
  • FIG. 26A described hereinafter
  • the variation of the particle size-determining and particle size distribution-generating method according to the first embodiment is distinguished from the particle size-determining and particle size distribution-generating method of the first embodiment in that by utilizing the fact that in general, in an emission spot (corresponding to timing T i in each of FIGS. 7A to 7 E) where the intensity of an emission spectrum emitted e.g. by Fe as an element forming the ground of a test sample is equal to or smaller than the threshold value, there exist intermetallic inclusions other than Fe, the data sorting process of FIGS. 8 to 10 is executed with Fe as a trigger concerning the timing T i .
  • an emission spot on the surface of a test sample has a circular shape of ⁇ 30 ⁇ m.
  • an Fe emission spectrum for example, emitted from Fe as a metal element which forms the ground of the test sample and has conductivity is obtained.
  • an element X as a constituent element of the intermetallic inclusion emits light, which makes the intensity of the Fe emission spectrum lower than that in the case of no intermetallic inclusion existing in the surface of the measurement area of the test sample.
  • FIGS. 7A to 7 E emission spots which are identical in the number of times of generation of spark discharge generated thereat are indicated as timing T i by broken lines.
  • timing T 1 indicated by broken lines it is estimated that there exists an intermetallic inclusion of Al 2 O 3 which is a compound composed of Al and O, except the case where there exist elements other than an element or elements to be determined and the lens is deteriorated, referred to hereinafter.
  • timing T 2 indicated by broken lines it is estimated that there exists intermetallic inclusions of Al 2 O 3 and CaO each of which is a compound composed of more than one element selected from Al, O and Ca.
  • FIG. 11 is a flowchart of a data sorting process which is executed by the variation of the particle size-determining and particle size distribution-generating method according to the first embodiment.
  • FIG. 11 data sorting process is distinguished from the FIG. 8 data sorting process in that a row A x is generated by deleting data of emission spots where the emission spectrum intensities of Fe are smaller than the threshold value specific to Fe (hereinafter referred to as “the threshold value Fe”) from each row I x of data items of emission spectrum intensities specific to each of elements X as constituent elements of the intermetallic inclusions.
  • the threshold value Fe the threshold value specific to Fe
  • a count i indicative of the number of data items in a row I Fe in which are arranged data of the emission spectrum intensities of Fe, fetched from the memory is set to 1
  • a count ii indicative of the number of data items in the row I Fe whose values are larger than the threshold value Fe is set to 0 (step S 1101 ).
  • one data item is fetched at random as a data item I Fe (i) from the rows I Fe stored in the memory in number corresponding to the number of times J (1000) of generation of spark discharge, and it is determined whether or not the fetched data item I Fe (i) is equal to or smaller than the threshold value Fe (step S 1102 ). If the fetched data item I Fe (i) is determined to be larger than the threshold value Fe in the step S 1102 , the count ii is incremented by 1 (step S 1103 ), followed by the process proceeding to a step S 1110 .
  • a count K indicative of the number of data items I Fe (i) whose values were determined to be equal to or smaller than the threshold value Fe is calculated by using the following equation (6) (step S 1104 ):
  • a step S 1105 one of elements (e.g. O, Ca, C, Ti, Mn, S and N) existing in the surface of measurement area of the test sample is selected as a constituent element X, and then data items I x (i) of the emission spectrum intensities of the constituent element X corresponding to emission spots of the fetched data items I Fe (i) are read out from a row I x of data of the emission spectrum intensities specific to the constituent element X, which are stored in the memory (step S 1106 ).
  • elements e.g. O, Ca, C, Ti, Mn, S and N
  • the fetched data items I x (i) are substituted for data items A x (K) in the row A x (step S 1107 ), and it is determined whether or not all the constituent elements existing in the surface of the measurement area have been selected. If not all the constituent elements have been selected in the step S 1108 , the process returns to the step S 1105 , whereas if all the constituent elements have been selected, the count K is regarded as a present maximum value of the count i at the time point that the data item I Fe (i) was read out at random, and substituted for K max (step S 1109 ).
  • step S 1110 it is determined whether or not the present count i is smaller than the number of times J (1000) of generation of spark discharge.
  • step S 1111 If the count i is smaller than the number of times J of generation of spark discharge, the count i is incremented by 1 (step S 1111 ), followed by the process returning to the step S 1102 , whereas if the count i is equal to or larger than the number of times J of generation of spark discharge, a constituent element X which is one of the elements constituting the intermetallic inclusion identified in the step S 605 is selected, followed by the process proceeding to the step S 901 (FIG. 9).
  • the process may proceed to the step S 801 in FIG. 8 and be subjected to the processing in FIG. 8, and then proceed to the step S 901 (FIG. 9).
  • the gist of the present variation of the particle size-determining and particle size distribution-generating method according to the first embodiment is as follows.
  • the threshold value for data items I Fe (i) is set to a lower value in the step S 1102 in FIG. 11, the values of the data row data A x (K) which are equal to or larger than the threshold value in the step S 1107 become larger than the values of the data items I x (i) and sufficiently exceed the threshold value in the step S 802 in FIG. 8 (fully satisfy the condition of I x (i) ⁇ threshold value in the step S 802 in FIG. 8).
  • the threshold value for data items I Fe (i) in the step S 1102 in FIG. 11 is properly set, the need for carrying out the threshold-comparison process executed in the step S 802 in FIG. 8 can be substantially eliminated.
  • the process can directly proceed to the step S 901 (FIG. 9) without passing through the FIG. 8 process, so that it is possible to shorten the processing time required for generation of a particle size distribution and so forth.
  • the data items I x (i) of the intensities of the emission spectra of an element X as a constituent element of an intermetallic inclusion include no data items A x (K) whose values are equal to or larger than the threshold value, it can be considered that there exist elements other than the element to be determined (e.g. a constituent element of a carbide, other than carbon) or the lens is stained or deteriorated.
  • elements other than the element to be determined e.g. a constituent element of a carbide, other than carbon
  • a correction process related to the stain/deterioration of the lens will be described in detail as part of a third embodiment, given hereinafter. Needless to say, it is preferable that the correction process according to the third embodiment is executed together with the variation of the particle size-determining and particle size distribution-generating method according to the first embodiment.
  • a bearing steel actually used as a material for rolling members such as a roller bearing, contains various kinds of intermetallic inclusions formed e.g. of Al 2 O 3 , MgO, MnS, CaO, and SiO 2 .
  • intermetallic inclusions formed e.g. of Al 2 O 3 , MgO, MnS, CaO, and SiO 2 .
  • the Al 2 O 3 inclusion which is an oxide-based inclusion, most seriously affects the rolling life of the bearing steel.
  • the method of determining the particle sizes and particle size distribution or abundance of the Al 2 O 3 inclusion includes two kinds of method, one of which is a three-dimensional method in which intermetallic inclusions are extracted from a sample of the bearing steel and the determination is carried out on the extracted intermetallic inclusions in a three-dimensional manner, such as an electron-beam elution method, and the other is a two-dimensional method in which the surface of a sample of the bearing steel is polished and the surface is subjected to the determination by a combination of an optical microscope and an image analyzer.
  • the former method requires a large-scale apparatus for extraction of the Al 2 O 3 inclusion, while the latter method is simple, but it is not capable of obtaining real particle sizes of the Al 2 O 3 inclusion.
  • the particle size-determining and particle size distribution-generating method according to the second embodiment is also implemented by the FIG. 1 emission spectrometer 100 to determine the particle sizes and particle size distribution of intermetallic inclusions contained in a test sample cut out from a steel material.
  • the present method uses a real steel master cut out from a real steel material.
  • the present method makes it a precondition that a calibration curve C, described hereinbelow, representative of the relationship between the concentration of Al and the emission spectrum intensity of Al is generated by using the FIG. 1 emission spectrometer 100 .
  • inclusions contained in the bearing steel are not only the Al 2 O 3 inclusion as described above, but since the Al 2 O 3 inclusion is most closely related to the rolling life of the bearing steel, the following description will be given by taking the Al 2 O 3 inclusion as an example. It goes without saying that other kinds of intermetallic inclusions can be dealt with similarly to the Al 2 O 3 inclusion.
  • the particle size-determining and particle size distribution-generating method of the second embodiment is distinguished from that of the first embodiment in which the particle size of Al 2 O 3 actually existing in the steel is determined by surface analysis by the EPMA method, in that the emission spectrometer 100 is used to determine the real particle size of the Al 2 O 3 inclusion.
  • the use of the calibration curve C representative of the relationship between the concentration of Al and the emission spectrum intensity of Al is effective in that it is possible to determine the particle sizes and particle size distribution of Al 2 O 3 particles actually existing in a steel based on Al concentration (volume %) at least in a range of the order of 500 ppm to the order of percent.
  • FIG. 1 emission spectrometer 100 A description will be given of a particle size-determining and particle size distribution-generating process executed by the FIG. 1 emission spectrometer 100 to implement the particle size-determining and particle size distribution-generating method of the second embodiment, with reference to the drawings.
  • FIG. 12 is a flowchart of the particle size-determining and particle size distribution-generating process executed according to the particle size-determining and particle size distribution-generating method of the second embodiment.
  • step S 1201 a calibration curves B, C generating process
  • step S 1202 a calibration curve D-forming process
  • step S 1203 a calibration curve E-generating process
  • step S 1204 a particle size distribution-generating process
  • an EPMA is not used, but the real particle sizes of intermetallic inclusions contained in a reference sample equivalent to a test sample is determined by using the emission spectrometer 100 , and a particle size distribution is generated based on the determined real particle sizes of the intermetallic inclusions.
  • FIG. 13 is a flowchart of the calibration curves B, C generating process which is executed in the step S 1201 in FIG. 12 for forming the calibration curve B representative of the relationship between the emission spectrum intensity of Fe and the concentration of Fe, and then forming the calibration curve C representative of the relationship between the emission spectrum intensity Al and the concentration of Al by the use of the calibration curve B.
  • the present calibration curve-forming process is carried out by the emission spectrometer 100 at least once before the method of determining the particle sizes of intermetallic inclusions and generating a particle size distribution is repeatedly executed on a test sample by the emission spectrometer 100 .
  • Seventeen types of Fe concentration masters (examples 1 to 17 shown in Table 1) are prepared whose Fe concentrations are already quantitatively determined e.g. by chemical analysis, such as an atomic absorption analysis method, and thus already known concentration values, and different from each other.
  • These masters may be formed of an alloy steel, such as M50, 5Cr, SUH330, SUH310, or M50NiL.
  • commercial masters sold by an external testing organization may be employed.
  • step S 1301 After each of these Fe concentration masters is held in the light emitting stand 102 of the emission spectrometer 100 of the present invention (step S 1301 ), the counter electrode of the light-emitting section 101 generates spark discharge e.g. ten times.
  • the Fe concentration masters subjected to spark discharge emit emission spectra (on a master-by-master basis) (step S 1302 ).
  • each master is separated by the concave diffraction grating 112 into emission spectra specific to Fe as the ground of the Fe concentration master (step S 1303 ), and the split Fe emission spectra are caused to enter the respective corresponding photomultipliers 113 via the exit slits 110 .
  • Each photomultiplier 113 detects the incoming Fe emission spectrum and converts the intensity of the detected Fe emission spectrum to an electric current value and transmits the current value to the photometric section 104 .
  • the photometric section 104 converts the received current value to a digital value and then transmits the digital value obtained by the conversion to the data processing section 106 via the interface 105 (step S 1304 ).
  • the light emitting stand 102 transmits data of the positions of emission spots of ⁇ 30 ⁇ m in an arbitrary measurement area on the surface of the Fe concentration master and the number of times of generation of spark discharge to the data processing section 106 via the interface 105 .
  • the Fe concentration masters have already known Fe concentration values, these known concentration values are input to the data processing section 106 as data of Fe concentration.
  • the data processing section 106 forms the calibration curve B (FIG. 14) representative of the relationship between the concentration of Fe and the emission spectrum intensity of Fe, based on the input data of Fe concentration [mass %] and the stored data of the emission spectrum intensity of Fe (step S 1305 ).
  • the number of times of generation of spark discharge caused per Fe concentration master in the step S 1302 is set to 10 times by way of example because it is preferable that the emission spectrum intensity is determined as an average value of emission spectrum intensities obtained ten times in this step. This makes it possible to make the average value of the emission spectrum intensities correspond to the Fe concentration of the one Fe concentration master.
  • steps S 1306 to S 1313 in FIG. 13 are executed to form the calibration curve C representative of the relationship between the emission spectrum intensity of Al and the concentration of Al.
  • cylindrical real steel masters of ⁇ 40 mm are cut out from a steel material for actual use, e.g. SUJ-2 in the form of a solid round rod, as shown in FIG. 15, and then held in the light emitting stand 102 (step S 1306 ).
  • FIG. 15 is a cross-sectional view of a steel material, taken along a section orthogonal to the axis of the steel material for actual use, from which the real steel masters are cut out in the step S 1306 in the FIG. 13.
  • the steel material 700 for actual use is produced by a method of blooming an ingot or a continuous method.
  • a molten material is cooled and solidified into the steel material 700 during the process of producing the same, in the core portion of the steel material 700 , where the cooling rate is smaller than in the outer peripheral portion of the same, there occurs a phenomenon that intermetallic inclusions 400 are concentrated (center segregation).
  • the center segregation is conspicuous in an area (center segregated portion 500 ) within a range of 0.5 D with respect to the diameter D of the steel material 700 , i.e. within a range of ⁇ 0.25 D from the center of the steel material 700 , and more conspicuous toward the center even in this center segregated portion 500 .
  • the center segregation is known to be correlated with the distance from the core portion, and hence by cutting out a portion of the steel material 700 including the core portion, along a plane perpendicular to the axis of the steel material 700 , it is possible to obtain a real steel master containing Al 2 O 3 inclusions varying in size with the distance from the core portion.
  • the Al 2 O 3 inclusions of various sizes contained in the real steel master include ones having Al concentrations at least in a range from the order of 500 ppm to the order of percent.
  • a real steel master containing Al 2 O 3 inclusions having various sizes by cutting out a portion of the steel material 700 including the core portion, along a plane perpendicular to the axis of the steel material 700 , so as to obtain a calibration curve in an Al concentration region ranging from a low concentration to a high concentration thereof.
  • a plurality of real steel masters 500 containing Al 2 O 3 inclusions of various sizes may be obtained by cutting out from the steel material 700 a plurality of pieces of the center segregated portion 500 in parallel with the axis of the steel material 700 .
  • the steel material 700 may also contain intermetallic inclusions other than Al 2 O 3 .
  • the counter electrode of the light-emitting section 101 generates spark discharge e.g. one thousand times at an arbitrary location on a measurement area ( ⁇ 5 mm) on the surface of the real steel master such that the diameter of each spot is held to ⁇ 30 ⁇ m (it is important that once arbitrarily set, the spot diameter should be held constant), the real steel master subjected to spark discharge emits emission spectra (step S 1307 ).
  • the intermetallic inclusions in the surface of the real steel master are dielectric, and hence at this time, the spark discharge is selectively guided to the intermetallic inclusions in the surface of the real steel master by the dielectric property thereof.
  • the emission spectra generated by the real steel master are selectively emitted from the intermetallic inclusions. Therefore, when Al 2 O 3 intermetallic inclusions exist in the surface of the real steel master, emission spectra containing information on Al and O as element information on Al 2 O 3 can be obtained.
  • the emission spectra emitted from Al 2 O 3 as the intermetallic inclusions of the real steel master are separated into emission spectra specific to the respective elements Fe, Al and O by the concave diffraction grating 112 (step S 1308 ), and the separated emission spectra of the respective elements enter the respective photomultipliers 113 via the corresponding exit slits 110 .
  • the photomultipliers 113 detect the incoming emission spectra of Fe, Al and O and convert the intensities of the detected emission spectra of the respective elements to electric current values and transmit the current values to the photometric section 104 .
  • the photometric section 104 converts each of the received current values to a digital value, and then transmits the digital value obtained by the conversion to the data processing section 106 via the interface 105 (step S 1309 ).
  • the light emitting stand 102 transmits data of the positions of emission spots of ⁇ 30 ⁇ m on the measurement area of ⁇ 5 mm on the surface of the real steel master or the distance from the center portion and the number of times of generation of spark discharge to the data processing section 106 via the interface 105 .
  • Fe concentration data [mass %] concerning the Fe concentrations [mass %] of the real steel master is generated, and then the generated Fe concentration data is stored (e.g. in a manner associated with spot positions in a sequence of times of spark discharge) in the memory of the data processing section 106 such that the stored data can be read out for use when the calibration curve C representative of the relationship between the Al concentration and the Al emission spectrum intensity is formed in steps S 1311 to S 1312 , referred to hereinbelow (step S 1310 ).
  • Al concentration data [mass %] of Al within Al 2 O 3 as the intermetallic inclusions is calculated from the Fe concentration data generated in the step S 1310 (step S 1311 ). This arithmetic operation is carried out using the following equation (7) stored in the data processing section 106 :
  • the above equation (7) is for calculating Al concentration data in the case of the intermetallic inclusions being Al 2 O 3
  • the intermetallic inclusions are SiO 2 , CaO or MgO
  • the atomic weight of a corresponding one of SiO 2 , CaO and MgO and the formula weight of the oxide inclusions can be applied to the equation (7) so as to calculate the corresponding one of Si concentration, Ca concentration and Mg concentration.
  • spark discharge is generated one thousand times, it is expected that approximately one thousand data items of the Al concentration data calculated as above are obtained. In short, a very large number of data items of Al concentration can be obtained with such a large number of times of generation of spark discharge. Then, the calibration curve C representative of the relationship between the Al concentration and the Al emission spectrum intensity is formed based on the Al concentration data items [mass %] and the emission spectrum intensities of Al (emitted from the real steel masters) at times of generation of spark discharge when the respective Al concentration data items were obtained (step S 1312 ).
  • a calibration curve C representative of the relationship between the Al concentration and the Al emission spectrum intensity in emission spots where the Al concentration is higher can be obtained, whereas when a test sample from a portion other than the center segregated portion 500 is used, a calibration curve C representative of the relationship between the Al concentration and the Al emission spectrum intensity in emission spots where the Al concentration is lower can be obtained.
  • this real steel master has a ground composed of Fe, which is preferable in that Al can be more correctly identified.
  • the formed calibration curve B is stored in the memory of the data processing section 106 (step S 1313 ), followed by terminating the process.
  • the calibration curve C is used when the calibration curve A is applied to an embodiment which is a combination of the particle size-determining and particle size distribution-generating method according to the first embodiment and the particle size-determining (using a calibration curve E described hereinafter with reference to FIG. 21) and particle size distribution-generating method according to the second embodiment.
  • the Al concentration data are determined based on the Fe concentration data, and as a result, even when the ground of the real steel master contains Mg whose emission wavelength is close to that of Al, it is possible to distinguish Al in an emission spectrum of Al-contained inclusions from M therein, and hence form a calibration curve C more accurately than when an Al alloy containing more Mg is used as a master.
  • FIG. 16 is a flowchart of the calibration curve D-forming process which is executed in the step S 1202 in FIG. 12 to form the calibration curve D concerning the emission spectrum intensity of Fe and the evaporation loss of Fe.
  • the present calibration curve forming process is executed by the emission spectrometer 100 at least once before the method of determining particle sizes and a particle size distribution of intermetallic inclusions contained in a test sample is repeatedly carried out by the emission spectrometer 100 .
  • a pure master formed of a steel material containing no Al 2 O 3 is held in the FIG. 1 emission spectrometer 100 (step S 1601 ), and spark discharge is generated on the pure master held in Ar (step S 1602 ), whereby spots of ⁇ 30 ⁇ m (which is always held constant once set to the diameter, as described above) are generated. Then, emission spectra of Fe from the spots are separated (step S 1603 ), and data of the emission spectrum intensities of Fe are transmitted (step S 1604 ). It is preferred that the pure master is formed of pure iron. At the time of emission, it is possible to form spot marks having various sizes in the master by changing the discharge voltage from 10 kV by ⁇ 30%.
  • spot marks 800 (FIG. 17) having various sizes formed at the time of the emission are observed three-dimensionally by a SEM to thereby measure the depth and diameter of each spot mark 800 (step S 1605 ) and determine the volume thereof. Then, the mass (evaporation loss) of Fe which existed in each emission spot is calculated based on the volume of the spot mark 800 and the density of Fe (7.86 g/cm 3 ), and the evaporation loss of Fe is input (step S 1606 ).
  • the evaporation loss of Fe is proportional to the emission spectrum intensity of Fe obtained under a discharge condition which caused the Fe evaporation loss (FIG. 18). Therefore, the proportional relationship is adopted as a calibration curve D (step S 1607 ), and the calibration curve D is stored in the memory of the data processing section 106 (step S 1608 ). The formation of the calibration curve D is carried out at least once.
  • the real particle size (particle size D) of an intermetallic inclusion, such as Al 2 O 3 , in an emission spot of ⁇ 30 ⁇ m formed by a single spark discharge generated on a test sample (an object to be inspected) containing the intermetallic inclusion, such as Al 2 O 3 , can be calculated by using the calibration curve D. In the following, the calculation method will be explained.
  • FIG. 19 is a flowchart of the calibration curve E-forming process which is executed in the step S 1203 in FIG. 12 to form the calibration curve E representative of the relationship between the emission spectrum intensity of Al and the Al particle size.
  • step S 1901 respective data items of the emission spectrum intensities of Fe, Al, (O) as information on the same emission spot transmitted in a step S 604 in FIG. 20 are fetched (step S 1901 ), and the fetched data item of Fe emission spectrum intensity is substituted into the calibration curve D stored in the memory of the data processing section 106 in the step S 1202 in FIG. 12, whereby an evaporation loss [ng] of Fe is calculated (step S 1902 ).
  • step S 1903 the data item of Al emission spectrum intensity emitted from the same emission spot is substituted into the calibration curve C stored as an Al calibration curve in the memory of the data processing section 106 in the step S 1201 in FIG. 12, whereby an Al concentration [mass %] is calculated (step S 1903 ).
  • the mass M of Al 2 O 3 is calculated from the evaporation loss [ng] of Fe and the Al concentration [mass %] determined as above, by using the following equation (8) (step S 1904 ):
  • the volume V of Al 2 O 3 is calculated from the mass M of Al 2 O 3 existing in a spot mark of ⁇ 30 ⁇ m corresponding to a unit volume and the density of Al 2 O 3 (3.90 g/cm 3 ), by using the following equation (9) (step S 1905 ):
  • the Al 2 O 3 particle having the volume V is regarded as a perfect sphere, and the particle size D (diameter) of the Al 2 O 3 particle regarded as the perfect sphere is calculated by using the following equation (10):
  • the concentration of Al contained in intermetallic inclusions can be determined based on the Al emission spectrum intensity obtained by emission spectral analysis, from the calibration curve C representative of the relationship between the Al emission spectrum intensity and the Al 2 O 3 particle size, so that it is possible to obtain the particle size D of the Al 2 O 3 particle regarded as the perfect sphere.
  • the Al 2 O 3 particle size can be determined based on the corresponding Al emission spectrum intensities by forming the calibration curve E, i.e. this relationship which is a correspondence between the concentration of Al as a constituent element of the intermetallic inclusions and the Al 2 O 3 particle size.
  • the Al concentration [%] on the left side is determined as a concentration [%] of Al existing in the spot mark of ⁇ 30 ⁇ m corresponding to the unit volume, by substituting the emission spectrum intensity of Al emitted from the spot mark into the calibration curve C.
  • the Fe evaporation loss [ng] on the right side is determined as an evaporation loss [ng] of Fe which existed in the spot mark of ⁇ 30 ⁇ m corresponding to the unit volume, by substituting the emission spectrum intensity of Fe emitted from the spot mark into the calibration curve D obtained based on the spark discharge at emission spots having the same diameter.
  • the concentration [%] of Al existing in the spot mark of ⁇ 30 ⁇ m corresponding to the unit volume can be converted to the mass A [ng] of Al.
  • the concentration of Al is determined for each spot of ⁇ 30 ⁇ m, and this is the same with a test sample, so that the weight of Al existing within an area of ⁇ 30 ⁇ m can be considered both for the calibration curve C and for the test sample.
  • the mass A [ng] of Al can be obtained as a ratio of the mass A [atomic weight of 26.8, formula weight of 54] of Al 2 to the mass M of Al 2 O 3 (formula weight of 102) as follows:
  • the calibration curve E (FIG. 21) for use in calculating Al 2 O 3 particle sizes based on the emission spectrum intensity of Al as a constituent element of the intermetallic inclusions can be formed (step S 1907 ).
  • the formed calibration curve E is stored (step S 1908 ), followed by terminating the calibration curve E-forming process which is executed in the step S 1203 in FIG. 12.
  • emission spectrum intensities of the test sample used in forming the calibration curve E in the FIG. 19 process emission spectrum intensities measured in steps S 601 to S 604 in FIG. 20, hereinafter referred to, may be utilized.
  • the calibration curve E has already been stored, it is possible to easily calculate the particle sizes D of intermetallic inclusions contained in the test sample from the emission spectrum intensities of the test sample measured in a FIG. 20 process, described below, based on the calibration curve E.
  • FIG. 20 is a flowchart of the particle size distribution-generating process which is executed in the step S 1204 in FIG. 12.
  • steps S 601 to S 605 and steps S 607 to S 608 are identical to those of the FIG. 6 particle size distribution-generating process of the first embodiment.
  • step S 601 a test sample (an object to be inspected) is held (step S 601 ), and spark discharge is generated e.g. one thousand times (step S 602 ), emission spectra are separated (step S 603 ), and data of emission spectrum intensities are transmitted (step S 604 ). Then, similarly to the processing in the step S 605 in FIG. 6, intermetallic inclusions are identified (step S 605 ). Since this example is a case where attention is paid to the Al 2 O 3 inclusions as intermetallic inclusions, from the emission spectrum intensities of lots of elements emitted by the spark discharge, only data containing information on Al, O, and Fe alone are extracted as follows.
  • an intermetallic inclusion particle size-calculating process for calculating the particle size D of the Al 2 O 3 from the Al emission spectrum intensity based on the calibration curve E is (step S 2006 ).
  • the obtained particle size D of the Al 2 O 3 is input as A x (K) in the FIG. 8 data sorting process, described hereinbefore, and after execution of the FIG. 9 data sorting process for rearranging particle sizes in size-increasing order and the FIG. 10 data sorting process for determining frequencies (step S 607 ), the data processing section 106 generates a diagram shown in FIG. 27A and stores the same in the memory, and at the same time displays the FIG. 27A diagram on the terminal unit(step S 608 ).
  • the particle size-determining and particle size distribution-generating method of the third embodiment is also carried out by the FIG. 1 emission spectrometer 100 , in generating a particle size distribution of intermetallic inclusions contained in a test sample cut out from a steel material.
  • the particle size-determining and particle size distribution-generating method of the third embodiment is distinguished from the particle size-determining and particle size distribution-generating method of the first and second embodiments in that compensation is made for attenuation of emission spectrum intensities due to stains on the condensing lens 108 .
  • FIG. 22 is a flowchart of the intermetallic inclusion particle size-determining and particle size distribution-generating process according to the third embodiment.
  • step S 201 the FIG. 2 calibration curve A-forming process in the first embodiment is executed (step S 201 ), a correction curve generating process, described hereinafter with reference to FIG. 23, is executed (step S 2201 ), and a particle size distribution-generating process, described hereinafter with reference to FIG. 25, is executed (step S 2202 ).
  • step S 201 has been described with reference to FIG. 2, and hence description thereof is omitted.
  • calibration curve A there may be used one used at least once in the FIG. 3 calibration curve A-forming process and stored in the memory of the data processing section 106 .
  • FIG. 23 is a flowchart of the intensity correction curve-generating process which is executed in the step S 2201 in FIG. 22.
  • the present process is also executed by the emission spectrometer 100 at least once before the particle size distribution-generating process for generating a particle size distribution of intermetallic inclusions in a test sample is repeatedly carried out by the emission spectrometer 100 (e.g. when the emission spectrometer 100 is installed in a quality inspection line).
  • step S 2301 first, after a master cut out from a steel material formed e.g. of SUJ2 containing Al 2 O 3 is held in the light emitting stand 102 (step S 2301 ), the surface of the master is scanned by the EPMA to thereby determine particle sizes of Al 2 O 3 existing in the surface of the master (step S 2302 ). Further, an Al 2 O 3 particle whose particle size is the closest to 15 ⁇ m of all the determined particle sizes is selected (step S 2303 ), and data of the location of the selected Al 2 O 3 particle is transmitted to the data processing section 106 (step S 2304 ), and the data processing section 106 stores the received data of the location in the memory thereof.
  • spark discharge is repeatedly generated on the selected Al 2 O 3 particle by the counter electrode of the light-emitting section 101 , and whenever spark discharge is generated one thousand times, the intensity of an emission spectrum then emitted from the selected Al 2 O 3 particle is measured (step S 2305 ).
  • Data of the measured emission spectrum intensity is transmitted to the data processing section 106 via the interface 105 (step S 2306 ).
  • the light emitting stand 102 transmits data of the number of times of generation of spark discharge to the data processing section 106 via the interface 105 .
  • the data processing section 106 stores the data of the emission spectrum intensity and the data of the number of times of generation of spark discharge which have been received in the memory thereof.
  • the data processing section 106 forms a intensity correction curve, described hereinafter with reference to FIG. 14, which is representative of the relationship between the number of times of generation of spark discharge and the amount of attenuation of emission spectrum intensity, based on the data of the number of times of generation of spark discharge and the emission spectrum intensities which have been stored in the memory (step S 2307 ), and stores the formed intensity correction curve in the memory (step S 2308 ), followed by terminating the present process.
  • a intensity correction curve described hereinafter with reference to FIG. 14, which is representative of the relationship between the number of times of generation of spark discharge and the amount of attenuation of emission spectrum intensity, based on the data of the number of times of generation of spark discharge and the emission spectrum intensities which have been stored in the memory (step S 2307 ), and stores the formed intensity correction curve in the memory (step S 2308 ), followed by terminating the present process.
  • FIG. 24 is a diagram showing the intensity correction curve formed in the step S 2201 in FIG. 22.
  • the amount of attenuation of emission spectrum intensity is calculated as the difference between an emission spectrum intensity corresponding to a 0-th spark discharge and an emission spectrum intensity corresponding to each 1000-th spark discharge, and indicated as a correction value on the ordinate.
  • an emission spectrum intensity before correction by I(i) is expressed by the following equation (12):
  • test sample can contain intermetallic inclusions other than Al 2 O 3 , it is desirable that the FIG. 25 intensity correction curve should be also formed for each of the other intermetallic inclusions, such as CaO.
  • an Al 2 O 3 particle whose particle size is as large as the size of an Al 2 O 3 particle contained in a test sample and the closest to 15 ⁇ m is selected (step S 2303 ), and the intensity of an emission spectrum emitted from the selected Al 2 O 3 particle is measured whenever spark discharge is generated one thousand times (step S 2305 ), whereby the intensity correction curve representative of the relationship between the number of times of generation of spark discharge and the amount of attenuation of emission spectrum intensity is formed based on the data of the number of times of generation of spark discharge and the emission spectrum intensity (step S 2307 ). Therefore, the formed intensity correction curve is based on the Al 2 O 3 particle having a particle size closest to that of the Al 2 O 3 particle contained in the test sample.
  • FIG. 25 is a flowchart of the particle size distribution-generating process which is executed in the step S 2202 in FIG. 22.
  • the present process is executed by the emission spectrometer 100 whenever particle size distribution of intermetallic inclusions contained in a test sample is repeatedly generated after the FIG. 23 process by the emission spectrometer 100 is executed at least once.
  • steps S 601 to S 605 and steps S 606 to S 608 are identical to those of the FIG. 6 process, and hence description thereof is omitted.
  • the steps S 601 to S 605 are executed.
  • the data processing section 106 corrects data of the emission spectrum intensity of each element stored in the memory, based on the data of the number of times of generation of spark discharge and the intensity correction curve stored in the memory (step S 2501 ), and stores the corrected data of the emission spectrum intensity of each element in the memory.
  • the steps S 606 to S 608 are executed, followed by terminating the present process.
  • the data processing section 106 corrects the data of the emission spectrum intensity of each element stored in the memory, based on the data of the number of times of generation of spark discharge and the intensity correction curve stored in the memory (step S 2501 ), it is possible to correct the emission spectrum in real time.
  • the attenuation of emission spectrum intensity due to stains on the condensing lens 108 is corrected based on the particle size-determining and particle size distribution-generating method according to the first embodiment, it may be corrected based on the particle size-determining and particle size distribution-generating method according to the variation of the first embodiment or the second embodiment.
  • the data processing section 106 may store calibration curves for intermetallic inclusions other than the Al 2 O 3 (e.g. CaO, SiO, MnS, etc.), or alternatively in the FIG. 23 process, the data processing section 106 may store calibration curves and intensity correction curves for the intermetallic inclusions other than Al 2 O 3 , to thereby generate particle size distributions of a plurality of kinds of intermetallic inclusions contained in the test sample at a time.
  • the data processing section 106 may store calibration curves and intensity correction curves for the intermetallic inclusions other than Al 2 O 3 , to thereby generate particle size distributions of a plurality of kinds of intermetallic inclusions contained in the test sample at a time.
  • intermetallic inclusions contained in a test sample are composed of two or more kinds of elements, it is possible to more easily identify whether constituent elements are single substances, or form a compound or a mixture.
  • the row AL x in which the data items I x are rearranged in intensity-increasing order is obtained, this is not limitative, but a row AL x in which the data items I x are rearranged in intensity-decreasing order may be obtained.
  • the arithmetic operations such as the data sorting, are carried out by the emission spectrometer 100 and the data processing section 106 , this is not limitative, but the arithmetic operations may be carried out by an arithmetic processor, a storage medium, or any other device which is capable of storing program modules for the arithmetic operations or executing programs for the arithmetic operations, in place of the emission spectrometer 100 and the data processing section 106 , or alternatively, a combination of these devices may be used.
  • the particle size-determining and particle size distribution-generating method according to the first embodiment was carried out.
  • a material of SUJ2 having a relatively high degree of pureness was prepared, and a cylindrical test sample having a diameter of ⁇ 40 mm was cut out from the prepared SUJ2 material. Then, after the FIG. 2 process was executed to thereby generate a particle size distribution of Al 2 O 3 existing in an area of ⁇ 5 mm at an arbitrary location on the surface of the test sample, the determined area of ⁇ 5 mm was scanned by the EPMA as well, whereby the particle size distribution of Al 2 O 3 was generated and confirmed.
  • FIGS. 26A and 26B are diagrams for comparison between the Al 2 O 3 particle size distribution (a) generated by execution of the FIG. 2 process and the particle size distribution (b) generated by the EPMA.
  • the intermetallic inclusion particle size distribution-generating method of the present invention is capable of quickly generating a particle size distribution of intermetallic inclusions.
  • the calibration curve B can be obtained even when Fe concentration is low, i.e. when the concentration of intermetallic inclusions is high, and it is possible to determine Al concentration with ease when there is no intermetallic inclusion other than Al 2 O 3 . Therefore, the calibration curve B and the calibration curve C can be directly obtained by the emission spectrometer 100 alone, without using the calibration curve A as shown in FIG. 5, which is formed by using the EPMA, more specifically, by using a steel material for actual use and without extrapolating a calibration curve covering a range of Al concentration in Al 2 O 3 from a trace concentration in the order of ppm to a considerably large concentration in the order of percent.
  • step S 1201 in FIG. 12 After the execution of the step S 1201 in FIG. 12, a cylindrical test sample having a diameter of ⁇ 40 mm was further cut out from a steel material containing no Al 2 O 3 , and the step S 1202 in FIG. 12 was executed. Then, discharge voltage to be applied to the test sample for emission spectral analysis was changed from 10 kV by ⁇ 30% to thereby determine the volumes of spot marks through the three-dimensional SEM observation, and the relationship between the amount of evaporation of Fe calculated based on the volumes of the spot marks and the density of Fe and the spot diameter of the spot marks was examined. The results of the examination are shown in Table 2 and FIG. 18.
  • a cylindrical test sample (an object to be inspected) having a diameter of ⁇ 40 mm was cut out from a SUT-2 material to be actually examined, and the particle size distribution of Al 2 O 3 existing in an area of ⁇ 5 mm at an arbitrary location on the surface of the object to be inspected was generated by execution of the FIG. 12 process. Then, a particle size distribution of Al 2 O 3 in the determined area of ⁇ 5 mm was also generated by the image analysis method and confirmed.
  • FIGS. 27A and 27B are diagrams for comparison between the Al 2 O 3 particle size distribution (a) generated by execution of the FIG. 12 process and the particle size distribution (b) generated by the image analysis method.
  • the comparison between the Al 2 O 3 particle size distribution (a) generated by execution of the FIG. 12 process and the particle size distribution (b) generated by the image analysis method showed that the Al 2 O 3 particle size distribution (a) generated by execution of the FIG. 12 process is more accurate than the particle size distribution (b) generated by the image analysis method in that lots of Al 2 O 3 particles having small particle sizes are extracted in the particle size distribution concerning the Al 2 O 3 inclusion in the steel as a material for roller bearings; lots of Al 2 O 3 particles within a range of 3 to 13 ⁇ m which affect the rolling life of the roller bearings are extracted; and a larger number of intermetallic inclusions are extracted as a whole.
  • FIG. 12 process gives more accurate results than the conventional extrapolation method in which high Al concentrations in the order of percent are extrapolated into a calibration curve, since the execution of the former provides the calibration curve B indicative of the concentration of Al in intermetallic inclusions covering up to high Al concentrations in the order of percent by using the actually used SUJ-2 material and the calibration curve D which estimates the real particle sizes of intermetallic inclusions, such as Al 2 O 3 , three-dimensionally and correctly. Further, since the FIG. 12 process is executed simply by using the emission spectral analysis, without preparing special masters or using the EPMA method, it is possible to provide a simple and easy particle size-determining and particle size distribution-generating method.
  • an intermetallic inclusion particle size-intensity calibration curve representative of the relationship between particle size of intermetallic inclusions and emission spectrum intensity of a constituent element of the intermetallic inclusions is formed. This makes it possible to identify what form is assumed by the intermetallic inclusions from elements constituting the intermetallic inclusions and quickly and accurately determine or measure particle sizes and particle size distribution of the intermetallic inclusions.
  • the particle size of the intermetallic inclusions in the predetermined area of the reference sample is determined through surface analysis by an electron probe microanalyzer. This enables quick and accurate determination or measurement of the particle size and particle size distribution of the intermetallic inclusions.
  • a principle component known concentration-intensity calibration curve representative of the relationship between the emission spectrum intensity of the principle component having an already known concentration and the known concentration of the principle component
  • a real steel material-contained intermetallic inclusion constituent element concentration-intensity calibration curve representative of the relationship between the concentration of the constituent element of the intermetallic inclusions and the emission spectrum intensity of the constituent element of the intermetallic inclusions
  • a base element evaporation amount-intensity calibration curve representative of the relationship between the base element evaporation amount and the intensity of emission spectra emitted from the base element.
  • an intermetallic inclusion particle size-intensity calibration curve representative of the relationship between the calculated particle size of the intermetallic inclusions and the determined emission spectrum intensity of the constituent element of the intermetallic inclusions. This enables quicker and more accurate determination of real particle sizes and particle size distribution of the intermetallic inclusions.
  • a data sorting process for counting the number of data items is executed to thereby generate a particle size distribution of the intermetallic inclusions in the test sample. This makes it possible to identify what form is assumed by the intermetallic inclusions from elements constituting the intermetallic inclusions and quickly and accurately determine or measure particle sizes and particle size distribution of the intermetallic inclusions.
  • the data items of emission spectra of the constituent element of intermetallic inclusions in the test sample are rearranged in order of intensity, and then the number of the rearranged data items is counted. This makes it possible to facilitate processing of the data.
  • data items of emission spectrum intensity of a constituent element of intermetallic inclusions in the test sample to be rearranged in order of intensity are extracted by determining whether or not an emission spectrum intensity of the constituent element of the intermetallic inclusions in the test sample is larger than a threshold value. This makes it possible to reduce the number of the data.
  • the data items of emission spectrum intensity of the constituent element of the intermetallic inclusions in the test sample to be rearranged in order of intensity are extracted based on a result of comparison between the emission spectrum intensity of a principle component of the test sample and the emission spectrum intensity of the constituent element of the intermetallic inclusions in the test sample. This makes it possible to reduce the number of the data and quickly extract data items to be rearranged in order of intensity.
  • emission spectrum intensity of a constituent element of the intermetallic inclusions in the test sample is corrected according to the number of times of generation of spark discharge. This enables quicker and more accurate determination or measurement of particle sizes and particle size distribution of the intermetallic inclusions.
  • a kind of the constituent element of the intermetallic inclusions is identified based on a result of comparison between the intensity of emission spectra of a principle component of the test sample and the intensity of emission spectra of the constituent element of the intermetallic inclusions in the test sample. This makes it possible to positively reduce the number of data items and more quickly and more accurately determine or measure particle sizes and particle size distribution of the intermetallic inclusions.

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