US3723279A - Apparatus for oxygen determination - Google Patents

Apparatus for oxygen determination Download PDF

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Publication number
US3723279A
US3723279A US00039530A US3723279DA US3723279A US 3723279 A US3723279 A US 3723279A US 00039530 A US00039530 A US 00039530A US 3723279D A US3723279D A US 3723279DA US 3723279 A US3723279 A US 3723279A
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US
United States
Prior art keywords
oxygen
oxygen content
steel
probe
tube
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Expired - Lifetime
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US00039530A
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English (en)
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R Fruehan
E Turkdogan
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STEEL Corp US
United States Steel Corp
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STEEL CORP
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/411—Cells and probes with solid electrolytes for investigating or analysing of liquid metals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/411—Cells and probes with solid electrolytes for investigating or analysing of liquid metals
    • G01N27/4115—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
    • G01N27/4117—Reference electrodes or reference mixtures

Definitions

  • the steel-making process can be considerably advanced if the amount of oxygen dissolved in molten steel is continuously and immediately known during the various stages of the process. Such knowledge would permit previously impossible manipulations of a melt of steel by providing better control of the oxidation and deoxidation reactions.
  • the oxygen content of liquid steel has heretofore been determined by the analysis of samples of the liquid steel.
  • the various analytical methods now used require elaborate equipment and do not provide results rapidly enough for best control of the steel-making process.
  • a solid oxide electrolyte galvanic cell with a gaseous reference electrode has been used in laboratory experiments to provide a rapid determination of oxygen in liquid steels, but these cells are not practical for use in steel production for various reasons. They are relatively expensive, their accuracy is not satisfactory, and their quality is not uniform nor satisfactory.
  • thermocouple is embedded into a condensed phase reference electrode which is placed inside the tube.
  • the thermocouple in addition to providing a temperature determination, serves as one connection to an oxygen indieating apparatus.
  • a dise of molybdenum cermet which contacts the liquid steel is also connected to the oxygen indicating apparatus by a -wire of the same material that connects the thermocouple to the oxygen indicating apparatus.
  • a metallic cap which dissolves in the liquid steel, protects the cell or probe from the slag when plunged into the melt.
  • Patented Mar. 27, 1973 Another object is to provide a disposable probe for determining oxygen content in molten metal ⁇ without sampling the melt.
  • a further object is to provide such a probe which iS relatively inexpensive, reliable and accurate.
  • a still further object is to provide such a probe that requires no thermo-electromotive force corrections.
  • Still another object is to provide such a probe which also determines the temperature of the liquid metal.
  • FIG. 1 is a sectional view of the oxygen probe of our invention and includes its connections to be oxygen and temperature indicating apparatus;
  • FIG. 2 is a graph showing the relationship between the measured EMF and oxygen content in parts per million
  • FIG. 3 is a graph comparing the measured oxygen content of liquid steel with the oxygen content determined by the neutron activation method of analysis.
  • reference numeral 2 indicates a calcia stabilized zirconia
  • Zr02(CaO) disc which is placed in one end of a refractory container 4.
  • Disc 2 may be fused to the bottom of a silica tube 4, or inserted into the bottom of an alumina tube 4.
  • Disc 2 is preferably about 3 mm. in diameter and 3 mm. high.
  • Contained in tube 4 above disc 2 is a mixture 6 of Cr and Cr2O3, about 90 to 98 weight percent Cr, the balance Cr203.
  • Partially embedded in the mixture 6 is a conventional thermocouple 8 having a double bore silica tube 10 and a pair of wires 12, preferably Pt-Pt/ 10% Rh in contact with the mixture 6. The upper ends of wires 12 are each connected to Contact prongs 14.
  • Tube 4 thermocouple 8 and part of prongs 14 are enclosed in an alumina container tube 16.
  • a Pt Wire 22 is attached to disc 18 and to a contact prong 24 through a silica protective tube 26.
  • Tube 16 is filled with a refractory cement 28, such as Alundum, which is an electrical and thermal insulator.
  • Tube 20 is filled with alumina powder 29.
  • the top of tube 16 is covered with a cap 30 made of a plastic, such as Teflon. Prongs 14 and 24 project through cap 30 to form an electrical plug.
  • An alumina support ring 32 is attached to the bottom of tube 16.
  • the bottom of tube 16 is sealed by a metal cap 34.
  • a long protective cardboard tube 36 rests on support rings 32.
  • a receptacle 3S fits over prongs 14 and 24 with lead wires 40 connecting prongs 14 and 24 to a temperature and oxygen indicator 42.
  • Prongs 14 and their respective lead wires 40 are compensating alloys conventional for a Pt-Pt/ 10% Rh thermocouple.
  • Prong 24 and its lead Wire 40 is the same compensating alloy as that connected to the Pt thermocouple wire.
  • Indicator 42 is preferably a potentiometric recorder or similar device with t-wo indicating arms. One indicating arm, for indicating temperature, is connected to wires 12.
  • a second indieating arm indicating in the range of minus 0.2 volt to plus 0.5 volt, is for oxygen content, and is connected to Wire 22 and Pt wire 12.
  • the probe In operation, the probe is plugged into a permanent receptacle provided at the furnace or ladle above the liquid metal L and then plunged into the melt to a suitable depth.
  • the cardboard tube 36 which extends above the top of the melt, protects the wires and upper elements of the probe from damage by the metal. lf the protective cardboard tube causes significant local carbon deoxidation, this may be overcome by replacing the last few inches of the cardboard tube with a refractory tube, such as silica.
  • Cap 34 protects the probe from chemical attack by the slag as the probe is lowered through the slag into the molten metal.
  • the cap 34 is made of material, such as copper or brass, which will not affect the oxygen content of the steel and which readily dissolves in the steel so as to expose the electrolyte and the molybdenum cermet disc to the molten steel.
  • the cap 34 may also be made of steel.
  • thermo-electromotive force corrections are required since all connections are at the liquid metal temperature and the lead wires will be at the same temperature. Fusing a small disc of electrolyte into the silica tube greatly increases its resistance to thermal shock.
  • Equation 5 neglects the effect of alloying elements in steel, the equation is essentially correct for low alloy steels.
  • An approximate correction for alloying elements can be made by the following expression:
  • a steady EMF is achieved in a few seconds after plunging the probe into the melt and provides continuous oxygen content readings up to 40 minutes.
  • the cell has sufficient reliability and accuracy for use in the steelmaking process as shown in FIG. 3 where the oxygen content of samples determined by the neutron activation method is compared with the oxygen content as measured by the EMF of the cell.
  • the electrolyte 2 must be a solid oxide and an oxygen ion conductor with insignificant electronic conductivity under the conditions of its use, particularly at the ternperature and oxygen partial pressure to which it is subjected. It must not react with the materials it contacts.
  • Zr02 with 3 to 10% by weight of Ca0 and Th02 with 3 to 20% by weight of Y203 are preferred for use with steel.
  • MgO, A1203, and Zr02 with 3 to 10% by weight of MgO or Y2O3 and Th02 with La203 may also be used, but electrolytes are not all suitable for use with all types of fluids.
  • the reference electrode y6 must be a condensed phase mixture of chromium and its oxide which does not readily melt at the temperature to which it is subjected nor react significantly with the materials it contacts. It is preferred to use a mixture of between about 90% to 98% by weight of pure chromium and the remainder Cr203. However, a chrome alloy may be substituted for the chromium. The alloying metal must be one having an oxide less stable than Cr203 so that Cr203 will be the equilibrium oxide phase. The melting point of the alloy must be high enough so that the alloy is solid at temperature of use. The dissociation pressure in Equation l would be corrected accordingly. Suitable alloys include up to 10% by weight of manganese or iron, or up to 5% nickel.
  • Mo cermet Mo 20% A1203
  • the material be an electronic conductor, will not melt at its temperature of use, will not readily dissolve in the fluid so that a steady and reliable voltage reading can be taken, and when dissolved in the liquid will not affect the voltage reading.
  • Such materials are Cr cermet (80% Cr, 20% Al203), Cr203, Mo wire or rod, Fe wire or rod and graphite rod. Not all materials can be used for all types of liquids.
  • a probe suitable for determining the oxygen content of liquid copper may have a reference electrode of Cr-Cr203, and a liquid metal contact of Cr cermet or Cr203.
  • the probe When used for determining the oxygen contents of the gases in soaking pits, heat treatment furnaces, hot exhaust gases or the like, the probe is altered slightly. Wire 22 must contact the electrolyte 2 where it is in contact with the gas and the cermet contact may be omitted. The balance of the probe is, of course, not in contact with the gas.
  • the specific probe described has been used in the oxygen content range from about 10 p.p.m. to about 1000 p.p.m. Below that concentration it is preferred to use ThO2(Y2O3), which will provide predominantly ionic con duction at oxygen contents down to 1 p.p.m.
  • the probe Since the probe is made of inexpensive materials and is relatively easy to manufacture, the probe can be used once and thrown away in the same manner that immersion thermocouples are used. Because a conventional thermocouple is incorporated into the probe, temperatures may be determined at the same time as oxygen content, and auxiliary equipment requirements are minimal.
  • a zirconia thimble small enough to avoid thermal shock, could be located in the lining of a tundish to contact the liquid steel with the other essential parts of the probe arranged in a manner already described.
  • Apparatus for determining the oxygen content of a fluid at a temperature of at least 700 C. which comprises a galvanic cell including a refractory container closed at one end thereof by a solid oxide electrolyte adapted to contact said fluid, and a reference electrode inside said refractory containers and in electrical contact with said electrolyte, said electrolyte being an oxygen ion conductor having insignificant electronic conductivity under conditions of use, said reference electrode being a mixture of Cr203 and a material of the class consisting of chromium and an alloy of chromium with a metal having an oxide less stable than Cr203, said material having a melting point such that it will be solid at the temperature of said fluid, and means for measuring the EMF of the cell when the electrolyte contacts the uid.
  • Apparatus according to claim 1 in which said electrolyte is of the group consisting of MgO, A1203, Zr02 with 3 to 10% by weight of CaO, ThO2 with 3 to 20% by weight of Y2O3, ZrOZ with 3 to 10% by weight of MgO, Zr02 with 3 to 10% by weight of Y2O3, and 'I'h02 with La203.
  • Apparatus according to claim 1 which includes a refractory electronic conductor adapted for electrical contact with said electrolyte, said conductor being made of material which is relatively insoluble in said uid, and means connecting said conductor and said reference electrode to said EMF measuring means.
  • said conductor is of the group consisting of a molybdenum cermet composed of about 80% by weight of Mo and about 20% by weight of A1203, a chromium cermet composed of about 80% by weight Cr and about 20% by weight of A1203, molybdenum, graphite and Cr203.
  • Apparatus in which said EMF measuring means is a two position potentiometric recorder; and which apparatus includes a thermocouple, said thermocouple having a junction embedded in said reference electrode, a first thermocouple wire connected to both potentiometric positions, and a second thermocouple wire connected to one potentiometric position to indicate temperature; and in which said means connecting said conductor to said EMF measuring means includes a junction of said conductor and a wire of the same material as vsaid first thermocouple wire, said last named wire being connected to the other potentiometric position to indicate oxygen content, and said junctions being located to operate at the same temperatures under conditions of use.
  • Apparatus according to claim 6 for use in a melt of steel having a layer of slag thereon, which apparatus includes a steel-soluble cap shielding said apparatus from slag upon immersion with said melt, said cap being of the group consisting of copper, brass, and steel.
  • Apparatus according to claim 7 which includes a refractory electronic conductor adapted to contact said melt, said conductor being made of material which is relatively insoluble in said melt, and means connecting said conductor and said reference electrode to said EMF measuring means.
  • said alloying metal is of the group consisting of up to 10% by weight manganese, up to 10% by weight iron and up to 5% by weight nickel.
  • Col 5p line 28 mwont-,aimersW should fread M- container msigned andv sealed this 20th day of Noven'ber 1973.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
US00039530A 1970-05-21 1970-05-21 Apparatus for oxygen determination Expired - Lifetime US3723279A (en)

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US (1) US3723279A (fr)
BE (1) BE767425R (fr)
FR (1) FR2093526A6 (fr)
GB (1) GB1352743A (fr)
IT (1) IT988017B (fr)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5029188U (fr) * 1973-07-11 1975-04-02
US3935079A (en) * 1972-11-03 1976-01-27 Fitterer Engineering Associates, Inc. Method and apparatus for displaying active oxygen and sensor temperature
FR2325928A1 (fr) * 1975-09-26 1977-04-22 Gen Electric Dispositif electrochimique pour la mesure de la concentration en oxygene d'un metal alcalin en fusion
US4045319A (en) * 1973-09-11 1977-08-30 Agence Nationale De Valorisation De La Recherche (Anvar) Electrochemical gage for measuring partial pressures of oxygen
US4046661A (en) * 1971-04-14 1977-09-06 Commonwealth Scientific And Industrial Research Organization Ceramic oxygen probe
US4152234A (en) * 1977-01-11 1979-05-01 Robert Bosch Gmbh Solid closed ended tubular oxygen sensor
US4198939A (en) * 1976-10-08 1980-04-22 Nissan Motor Company, Limited Method of controlling the air-fuel ratio of an engine air-fuel mixture and a system for executing the method
US4238308A (en) * 1977-09-30 1980-12-09 Sybron Corporation Device for monitoring a component in a fluid mixture
FR2469709A1 (fr) * 1979-08-31 1981-05-22 Unisearch Ltd Procede et appareil de mesure du potentiel d'oxydo-reduction de masses fondues a conductibilite ionique
US4342633A (en) * 1978-04-06 1982-08-03 Electro-Nite Co. Oxygen sensor
US4378279A (en) * 1981-08-31 1983-03-29 Uop Inc. High temperature electrical connection and method of producing same
DE3346658C1 (de) * 1983-12-23 1985-07-25 Ferrotron Elektronik Gmbh Vorrichtung zum Messen des Sauerstoffgehaltes und der Temperatur von Metallschmelzen waehrend des Frischens in einem Konverter
US4944861A (en) * 1989-04-03 1990-07-31 Barber-Colman Company Oxygen sensing probe having improved sensor tip and tip-supporting tube
US5596134A (en) * 1995-04-10 1997-01-21 Defense Research Technologies, Inc. Continuous oxygen content monitor
US5851369A (en) * 1996-09-20 1998-12-22 Marathon Monitors, Inc. Electrolytic sensor providing controlled burn-off of deposits on the electrodes
US6083368A (en) * 1996-04-20 2000-07-04 Kawaso Electric Industrial Co., Ltd. Probe device for continuous measurements of oxygen in running molten metal

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4046661A (en) * 1971-04-14 1977-09-06 Commonwealth Scientific And Industrial Research Organization Ceramic oxygen probe
US3935079A (en) * 1972-11-03 1976-01-27 Fitterer Engineering Associates, Inc. Method and apparatus for displaying active oxygen and sensor temperature
JPS5029188U (fr) * 1973-07-11 1975-04-02
US4045319A (en) * 1973-09-11 1977-08-30 Agence Nationale De Valorisation De La Recherche (Anvar) Electrochemical gage for measuring partial pressures of oxygen
FR2325928A1 (fr) * 1975-09-26 1977-04-22 Gen Electric Dispositif electrochimique pour la mesure de la concentration en oxygene d'un metal alcalin en fusion
US4198939A (en) * 1976-10-08 1980-04-22 Nissan Motor Company, Limited Method of controlling the air-fuel ratio of an engine air-fuel mixture and a system for executing the method
US4152234A (en) * 1977-01-11 1979-05-01 Robert Bosch Gmbh Solid closed ended tubular oxygen sensor
US4238308A (en) * 1977-09-30 1980-12-09 Sybron Corporation Device for monitoring a component in a fluid mixture
US4342633A (en) * 1978-04-06 1982-08-03 Electro-Nite Co. Oxygen sensor
FR2469709A1 (fr) * 1979-08-31 1981-05-22 Unisearch Ltd Procede et appareil de mesure du potentiel d'oxydo-reduction de masses fondues a conductibilite ionique
US4378279A (en) * 1981-08-31 1983-03-29 Uop Inc. High temperature electrical connection and method of producing same
DE3346658C1 (de) * 1983-12-23 1985-07-25 Ferrotron Elektronik Gmbh Vorrichtung zum Messen des Sauerstoffgehaltes und der Temperatur von Metallschmelzen waehrend des Frischens in einem Konverter
US4944861A (en) * 1989-04-03 1990-07-31 Barber-Colman Company Oxygen sensing probe having improved sensor tip and tip-supporting tube
US5596134A (en) * 1995-04-10 1997-01-21 Defense Research Technologies, Inc. Continuous oxygen content monitor
US6083368A (en) * 1996-04-20 2000-07-04 Kawaso Electric Industrial Co., Ltd. Probe device for continuous measurements of oxygen in running molten metal
US5851369A (en) * 1996-09-20 1998-12-22 Marathon Monitors, Inc. Electrolytic sensor providing controlled burn-off of deposits on the electrodes

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Publication number Publication date
IT988017B (it) 1975-04-10
BE767425R (fr) 1971-11-19
GB1352743A (en) 1974-05-08
FR2093526A6 (fr) 1972-01-28

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