EP1178122A2 - Procédure pour déterminer le potentiel d'oxydation d'une atmosphère gaseuse par rapport à métal/oxydes métalliques - Google Patents

Procédure pour déterminer le potentiel d'oxydation d'une atmosphère gaseuse par rapport à métal/oxydes métalliques Download PDF

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Publication number
EP1178122A2
EP1178122A2 EP01116252A EP01116252A EP1178122A2 EP 1178122 A2 EP1178122 A2 EP 1178122A2 EP 01116252 A EP01116252 A EP 01116252A EP 01116252 A EP01116252 A EP 01116252A EP 1178122 A2 EP1178122 A2 EP 1178122A2
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European Patent Office
Prior art keywords
oxygen partial
partial pressure
metal
gas atmosphere
equilibrium
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German (de)
English (en)
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EP1178122A3 (fr
Inventor
Rainer Gorris
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/10—Oxidising

Definitions

  • the invention relates to the definition and method for calculating a characteristic number with which the measured oxygen partial pressure in a gas can be represented in such a way that the oxidation or reduction potential of this gas atmosphere in relation to a metal which is exposed to this gas atmosphere in the form of a simple characteristic number is expressed which is independent of the temperature of the gas or the metal.
  • Metals that are exposed to a gas atmosphere can either be oxidized by this or be reduced or the atmosphere is neutral towards a metal.
  • Metallic materials are e.g. Iron, chrome, nickel, manganese, magnesium or aluminum but also silicon.
  • Inert gases such as Nitrogen, argon, helium or CO2 (only ⁇ 500 ° C) do not react with the metals or metal oxides.
  • Reaction gases are e.g. Mixtures of hydrogen, water vapor, carbon monoxide or dioxide (mostly in Combination with inert gases) and can be used with both metals and Metal oxides react and either oxidize or reduce them.
  • the oxygen partial pressure is used, which consists of a mixture a metal and its oxides in a certain atmosphere depending on the temperature.
  • Such measurements are often carried out with inert gases.
  • a mixture of the metal / metal oxide e.g. heated under nitrogen and the resulting equilibrium partial pressure of oxygen was measured.
  • the rest lead Oxygen contents of the neutral gas used to form metal oxides up to the equilibrium oxygen partial pressure is established.
  • the metal oxide still contains pure metal is the equilibrium oxygen partial pressure constant, i.e. regardless of the metal / metal oxide mixing ratio.
  • the equilibrium oxygen partial pressure values are for many metal-metal oxide mixtures known and can be found in tables.
  • the diagrams A and B are the curves (a) for Ni / NiO, Mo / Mo2, Fe / FeO, Cr / Cr2O3 and Mn / MnO for a temperature range of approx. 400 to 1400 ° C is shown.
  • the values are very low and are between 10exp -6 (1 ppm) and 10exp -50. They are very temperature dependent, so that in diagrams A and B the oxygen partial pressure in logarithmic Form (log pO2) was shown.
  • the workpieces are heated in an oven and protective gases mostly supplied continuously in the form of inert or reaction gases.
  • protective gases mostly supplied continuously in the form of inert or reaction gases.
  • oxygen usually enters the furnace through e.g. leaks or locks, through the continuously supplied protective gas, through residual oxygen in the pores of the furnace insulation or also through the heat treatment material itself (pores, Oxide layers).
  • CH4 methane
  • the values of the oxygen partial pressure lie in a mixture of 20% H2 and 80% N2 between the equilibrium oxygen partial pressures of Fe / FeO and Cr / Cr2O3 and bright annealing is possible, i.e. oxide layers present on the workpieces are reduced again.
  • the equilibrium shift can also be used to interpret oxygen partial pressure measurements the oxygen partial pressures of the gases with changed temperatures to be of importance.
  • Fe / FeO change e.g. the oxygen partial pressures for gases consisting of nitrogen or (nitrogen + hydrogen), when cooling or heating in virtually the same manner as the equilibrium partial pressure of oxygen of Fe / FeO, as our own measurements and calculations show.
  • Diagrams A and B show oxygen measurements from furnaces that pass through locks in the Principle are fed continuously.
  • a frequently used "auxiliary method” for this is the measurement of the gas dew point. From this, the H2O content can be determined according to tables. If the H2O content is related to the hydrogen content in the gas, this gives a ratio for the limit to "bright annealing". Diagram A shows the H2 / H2O values for Fe / FeO (f). They vary from 0.3 at approx. 550 ° C to 0.9 at approx. 1180 ° C.
  • the disadvantage of dew point measurement is, among other things, the required knowledge of the H2 content, which either has to be measured with great effort or is known - with mostly high error tolerances - as a prerequisite. Another disadvantage is that each gas temperature has a different limit.
  • the two back-calculated oxygen partial pressures coincide with the values of the equilibrium oxygen partial pressure of Fe / FeO.
  • the same result is achieved by directly measuring the oxygen partial pressure.
  • the big advantages are that only one gas component has to be determined and that the measurement values regardless of knowledge of the other gas components for the assessment can be used directly in an oven atmosphere.
  • the extremely low oxygen partial pressures can be measured with zirconium dioxide probes determine with certainty.
  • the interpretation of the measurement results relies on the oxidation / reduction potential of the gas that the gas and the workpiece are at the same temperature. In particular In the case of unsteady annealing processes, however, considerable differences can occur.
  • the aim of this invention is to define a characteristic number with which the measured oxygen partial pressure in a gas can be represented in such a way that the oxidation or reduction potential of this gas atmosphere in relation to a metal which is exposed to this gas atmosphere is expressed in the form of a simple characteristic number can be independent of the temperature of the gas or that of the metal (at the same temperature).
  • the key figure is to be named in the following with the REDOX number.
  • FIG. 1 shows an example with reference to the Fe / FeO equilibrium partial pressure of oxygen the resulting REDOX numbers (3).
  • the logarithms of the oxygen partial pressures for the calculation of the REDOX number used were used.
  • REDOX numbers can also be used in the same way for other metal / metal oxide equilibria define if this for the assessment of the gas atmosphere of are of particular importance (e.g. for Ni / NiO).
  • the REDOX number it can also be advantageous to use this according to claim 1.3 from the difference between the equilibrium oxygen partial pressure of a metal-metal oxide and the measured value of the oxygen partial pressure of the gas at each to form the same temperature.
  • Disadvantageous compared to that described above The division's method, however, is that the REDOX number formed by subtraction can usually only be related to a metal-metal oxide, since the course of the Equilibrium oxygen partial pressures of the individual metal-metal oxides with the temperature is usually not parallel [diagram A, B, curves (a)].
  • the oxygen partial pressures of the gas and / or the metal-metal oxides can be used for the calculation the key figure can be used as its real values, or by any mathematical transformations such as Logarithmic, exponentiate, multiply, Divide, add or subtract etc. be reshaped.
  • Those formed by the two basic methods of division and subtraction Ratios can be calculated by any other mathematical operations such as Logarithmic, exponentiate, multiply, divide, add or subtract et al to be reshaped in such a way that it is appropriately adapted REDOX number results.
  • the equilibrium shift of the oxygen partial pressures of a gas differ from that of a considered metal / metal oxide system.
  • This compensation can be carried out for all types of gases, e.g. reactive Components such as CO, CO2, H2, H2O and others contained in any combination or quantity.
  • the REDOX number curves (2) were calculated from the pure division of the logarithms of the equilibrium oxygen partial pressure a mixture of Fe / FeO (4) by the measured Partial oxygen pressure is formed in the gas at the same temperature in each case.
  • a gas from whose partial pressure of oxygen a REDOX number of ⁇ 1.0 is calculated, would be reducing compared to Fe / FeO or Mo / MoO, with REDOX numbers> 1.0 that would be Gas oxidizing effect.
  • the REDOX numbers are the equilibrium oxygen partial pressures deviates above the temperature, but they can usually also be used well. (If, for example, Ni / NiO were of particular importance, one could do so another REDOX number based on the equilibrium partial pressure of Ni / NiO To be defined).
  • the calculation method chosen here for the REDOX number results in a lower one Temperatures a "fanning out" of the curves, i.e. the differences in oxygen partial pressure increase with the same difference in the REDOX number. This results in a certain Compensation for the tendency that the reaction rates decrease with decreasing The temperature also decreases, and with it the same differences in the oxygen partial pressure have a lower oxidizing or reducing effect ("kinetic factor"). (If this is not desired, then the method of subtraction in accordance with claim 1.3 Calculation of the REDOX number can be used).
  • the representation of the REDOX number according to FIG. 1 has the advantage that the for glow processes mostly important oxygen range> approx. 1 EXP-10 bar a relatively fine one Gradation of the REDOX numbers results in an ever coarser with higher oxygen values Gradation takes place.
  • the REDOX number provides usable values in this representation down to the area of oxidation. For example, at 1000 ° C a REDOX number of 8.0 an oxygen content of approx. 1%.
  • the REDOX number can thus be used consistently as the only key figure, which is a great advantage when it comes to graphical representation on recorders and for the use of controllers.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Investigating And Analyzing Materials By Characteristic Methods (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)
EP01116252A 2000-07-07 2001-07-05 Procédure pour déterminer le potentiel d'oxydation d'une atmosphère gaseuse par rapport à métal/oxydes métalliques Withdrawn EP1178122A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10032411 2000-07-07
DE2000132411 DE10032411A1 (de) 2000-07-07 2000-07-07 Kennzahl zur Charakterisierung des Reduktions- oder Oxidationspotentials von Gasatmosphären in Bezug auf Metall-Metalloxide

Publications (2)

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EP1178122A2 true EP1178122A2 (fr) 2002-02-06
EP1178122A3 EP1178122A3 (fr) 2002-02-27

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EP01116252A Withdrawn EP1178122A3 (fr) 2000-07-07 2001-07-05 Procédure pour déterminer le potentiel d'oxydation d'une atmosphère gaseuse par rapport à métal/oxydes métalliques

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EP (1) EP1178122A3 (fr)
DE (1) DE10032411A1 (fr)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3883408A (en) * 1972-05-03 1975-05-13 Inland Steel Co Furnace atmosphere oxygen analysis apparatus
JPS5613430A (en) * 1979-07-14 1981-02-09 Nisshin Steel Co Ltd Annealing method of steel
JPH0611886B2 (ja) * 1983-12-14 1994-02-16 関東冶金工業株式会社 金属部品のガス雰囲気熱処理法
US5261976A (en) * 1991-12-31 1993-11-16 Gas Research Institute Control system for a soft vacuum furnace
JPH06145781A (ja) * 1992-11-02 1994-05-27 Nippon Techno:Kk 雰囲気熱処理炉
US5772428A (en) * 1996-02-09 1998-06-30 Praxair Technology, Inc. Method and apparatus for heat treatment including H2 /H2 O furnace region control
DE19736514C5 (de) * 1997-08-22 2004-11-25 Messer Griesheim Gmbh Verfahren zum gemeinsamen Oxidieren und Wärmebehandeln von Teilen

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EP1178122A3 (fr) 2002-02-27
DE10032411A1 (de) 2002-01-17

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