WO2003104514A1 - Generation d'atmospheres s'appliquant a la cementation au carbone a productivite elevee - Google Patents

Generation d'atmospheres s'appliquant a la cementation au carbone a productivite elevee Download PDF

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Publication number
WO2003104514A1
WO2003104514A1 PCT/US2003/017076 US0317076W WO03104514A1 WO 2003104514 A1 WO2003104514 A1 WO 2003104514A1 US 0317076 W US0317076 W US 0317076W WO 03104514 A1 WO03104514 A1 WO 03104514A1
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WO
WIPO (PCT)
Prior art keywords
central tube
furnace
gas mixture
gas
carburizing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2003/017076
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English (en)
Inventor
Jaak Stefaan Van Den Sype
Alan Russell Barlow
Edison Viotto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Praxair Technology Inc
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Praxair Technology Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US10/162,754 external-priority patent/US6969430B2/en
Application filed by Praxair Technology Inc filed Critical Praxair Technology Inc
Priority to AU2003243343A priority Critical patent/AU2003243343A1/en
Publication of WO2003104514A1 publication Critical patent/WO2003104514A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces

Definitions

  • This invention relates to a process and apparatus for producing atmospheres for high productivity carburizing. More particularly, this invention is directed to a process and apparatus for producing an atmosphere suitable for accelerated carburizing process using noble metal catalyst.
  • Carburizing is a widely used process for hardening the surface of steel parts by diffusion of carbon into the steel surface at high temperature .
  • the carbon is supplied to the steel surfaces by a carrier gas having a high carbon potential.
  • the most commonly used carburizing gas mixture is an endothermic gas which consists of 20% carbon monoxide (CO) , 40% hydrogen (H 2 ) and 40% nitrogen (N 2 ) . It is believed that the dominant reaction at the surface of the steel during the carburizing process is:
  • the rate at which carbon is put into the steel is therefore proportional to the product of the CO and H 2 concentration in the carrier gas. It is believed that the most productive reactive makeup for the reactant is a 50% CO and 50% H 2 mixture . This mixture may decrease the carburizing times by as much as 50%, thereby doubling the furnace productivity.
  • there is presently no practical and economical generator available to produce carburizing gas with high percentage of CO and H 2 It would therefore be a benefit in the art to provide a process and apparatus for producing carburizing gas with a high percentage of CO and H 2 .
  • Another method involves direct injection of methane (CH 4 ) and carbon dioxide (C0 2 ) into the furnace, as in U.S. Patent No. 5,676,769. Theoretically, this method can generate a 50% CO and 50% H 2 mix in the furnace using the reaction:
  • This invention is directed to a process for carburizing steel parts in a furnace comprising introducing into the furnace a gas mixture comprising CO, H 2 , C0 2 , H 2 0, CH 4 and N 2 such that the product of the %CO and %H 2 is greater than about 1600, preferably greater than 2000; the ratio of CO/C0 2 is greater than 10; and the ratio of H 2 /H 2 0 is greater than about 10; and controlling the gas mixture in the furnace for less than about 5 minutes, preferably less than 3 minutes, and most preferably less than 1 minute .
  • this invention is directed to a process for carburizing steel parts in a furnace comprising introducing into the furnace a gas mixture comprising CO, H 2 , C0 2 , H 2 0, CH 4 and N 2 such that the product of the %CO and %H 2 is greater than about 1600, preferably greater than about 2000; the ratio of C0/C0 2 is greater than 10; and the ratio of H 2 /H 2 0 is greater than about 10, the gas mixture being generated by a mixture of CH 4 and C0 2 over a noble gas catalyst, preferably platinum or rhodium, on an metallic carrier, preferably alumina carrier, at the temperature range of between about 850°C and 950°C; and controlling the gas mixture in the furnace for less than about 5 minutes .
  • a gas mixture comprising CO, H 2 , C0 2 , H 2 0, CH 4 and N 2 such that the product of the %CO and %H 2 is greater than about 1600, preferably greater than about 2000; the ratio of C0/C0 2 is greater than 10;
  • this invention is directed to a reactor for generating a gas mixture for carburizing steel which comprises a cylindrically symmetric body; a first central tube containing electrical heating elements for gas flow; a second central tube concentrically disposed around the first central tube; and a plurality of catalyst beds disposed in an annular space in a segmented fashion around the second central tube. There may be six catalyst beds disposed in an annular space in a segmented fashion around the second central tube.
  • the electrical heating elements maintain the gas mixture about 850°C to about 950°C.
  • FIG. 1 is a drawing of the reactor for use in this invention.
  • This invention involves a process for carburizing steel parts in the temperature range of 900°C to 960°C in which the rate of carburization is enhanced by:
  • [0015] introducing into the furnace a gas mixture having CO, H 2 C0 2 , H 2 0, CH and N 2 , such that the product (%C0)*(%H 2 ) is greater than 1600, preferably greater than 1000, and the ratio of CO/C0 2 and H 2 /H 2 0 in the gas mix is greater than 10.
  • This combination provides a gas with a high carbon potential and thereby minimizes the need for extensive reforming of C0 2 and H 2 0 in the furnace by injection of enriching gas (CH 4 or Propane) . This process is believed to avoid furnace sooting.
  • the residence time of the gas mixture in the furnace is kept short, preferably less than 5 minutes, more preferably less than 3 minutes, and most preferably about 1 minute. This process effectively purges the furnace of the H 2 0 generated by combining CO and H 2 , and again minimizes the need for large amounts of enriching gas.
  • the gas mixture is economically produced in a novel generator.
  • mixtures of CH 4 and C0 2 with possible additions of 0 2 , air and/or electrical heat, are introduced over a noble metal catalyst, preferably platinum or rhodium, on an alumina carrier in the temperature range of between 850°C to 950°C.
  • a noble metal catalyst preferably platinum or rhodium
  • Palladium and iridium are alternative noble metal catalyst.
  • Silica, zeolite and zirconia are alternative supports.
  • (%CO)*(%H 2 ) is about 2300.
  • the %C0 was 44%
  • C0 2 was 0.5%
  • High CO/H 2 mixtures are prepared in a separate reactor by reforming a CH 4 /C0 2 mixture over a noble metal catalyst . This avoids control problems associated with direct injection of CH 4 /C0 2 into the furnace .
  • a convenient method of producing gas mixtures with high (%CO)*(%H 2 ) product values is to first combust natural gas with 0 as in step 1 below. Part or all of the water is removed and the remainder CH 4 /C0 2 /H 2 0 mixture is reformed over a noble metal catalyst as in step 2.
  • Fig. 1 provides an example of such a reactor.
  • the reactor 10 is preferably cylindrically symmetric.
  • a central tube 12 is provided which contains electrical heating elements 14 or in which combustion gases flow in countercurrent with the CH 4 /C0 2 /0 2 or air mix. This mix is introduced into the reactor in the annular space defined by a second tube 16 concentrically disposed around the central tube.
  • Six catalyst beds 18 are disposed in this annular space in a segmented fashion.
  • the catalyst beds are in the shape of doughnuts and the spacing between them is such that the central tube 12 reheats the reacting gases to about 900°C before they contact the next catalyst bed.
  • the gas mixture introduced to the reactor is preheated to about 900°C using a conventional gas to gas heat exchanger using the exit gas from the reactor and/or combustion gases from the reactor. Electrical heat can also be used for preheating the gas mix.
  • Six catalyst beds 18 and electrical heating in the central tube 12 is suitable, although any number of catalyst beds are believed to be operational . Another preferred embodiment is the use of ten catalyst beds.
  • the electrical heating elements maintain the temperature of the gas mixture between about 750°C to about 1050°C, more preferably between about 800°C to about 1000°C, and most preferably between about 850°C to about 950°C.
  • the control of the accelerated carburizing process can be done by conventional means .
  • such means may include oxygen probes, CO/C0 2 measurements or H 2 0 measurements.
  • the CO level must be measured in the furnace since the percent of CO in the furnaces is typically in excess of 30% and may vary.
  • the carbon potential is set to equal or exceed the solubility of carbon in austenitic phase of the alloy being treated. Typically, this can be up to about 1.4%. This results in rapid saturation of the surface with carbon.
  • the carbon potential in the gas phase can be lowered to match the desired surface carbon level (e.g., 0.8% C) in the part being treated. This lower carbon level can be conveniently achieved in the accelerated carburizing gas by dilution with N 2 .

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Hydrogen, Water And Hydrids (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

Cette invention porte sur un procédé et sur un appareil utilisés dans des opérations de cémentation au carbone à productivité élevée. Le procédé utilise un mélange gazeux constitué de CO, H2, CO2, H2O, CH4 et N2 de sorte que le produit du %CO et de %H2 soit supérieur à environ 1600; que le rapport de CO/CO2 soit supérieur à 10 et que le rapport de H2/H2O soit supérieur à environ 10. Le mélange gazeux est contrôlé sur une courte durée. L'invention porte également sur un réacteur (10) destiné à générer un mélange gazeux pour cémenter l'acier. Ce réacteur est composé d'un corps symétrique, cylindrique ; d'un premier tube central (12) contenant des éléments chauffants électriques (14) pour l'écoulement gazeux; d'un second tube central (16) disposé de manière concentrique autour du premier tube central (12) et d'une pluralité de lits catalyseurs (18) disposés dans un espace annulaire, de façon segmentée, autour du second tube central (12).
PCT/US2003/017076 2002-06-05 2003-05-30 Generation d'atmospheres s'appliquant a la cementation au carbone a productivite elevee Ceased WO2003104514A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003243343A AU2003243343A1 (en) 2002-06-05 2003-05-30 Producing atmospheres for high productivity carburizing

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US10/162,754 2002-06-05
US10/162,754 US6969430B2 (en) 2002-06-05 2002-06-05 Process and apparatus for producing atmosphere for high productivity carburizing
US10/440,093 2003-05-19
US10/440,093 US20030226620A1 (en) 2002-06-05 2003-05-19 Process and apparatus for producing amtospheres for high productivity carburizing

Publications (1)

Publication Number Publication Date
WO2003104514A1 true WO2003104514A1 (fr) 2003-12-18

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PCT/US2003/017076 Ceased WO2003104514A1 (fr) 2002-06-05 2003-05-30 Generation d'atmospheres s'appliquant a la cementation au carbone a productivite elevee

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Country Link
US (1) US20030226620A1 (fr)
AU (1) AU2003243343A1 (fr)
WO (1) WO2003104514A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4049473A (en) * 1976-03-11 1977-09-20 Airco, Inc. Methods for carburizing steel parts
US4145232A (en) * 1977-06-03 1979-03-20 Union Carbide Corporation Process for carburizing steel
US5417774A (en) * 1992-12-22 1995-05-23 Air Products And Chemicals, Inc. Heat treating atmospheres

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4049472A (en) * 1975-12-22 1977-09-20 Air Products And Chemicals, Inc. Atmosphere compositions and methods of using same for surface treating ferrous metals
US4306918A (en) * 1980-04-22 1981-12-22 Air Products And Chemicals, Inc. Process for carburizing ferrous metals
FR2527641A1 (fr) * 1982-05-28 1983-12-02 Air Liquide Procede de traitement thermique de pieces metalliques par carburation
JP3448789B2 (ja) * 1995-01-20 2003-09-22 同和鉱業株式会社 ガス浸炭方法
US6287393B1 (en) * 1999-09-03 2001-09-11 Air Products And Chemicals, Inc. Process for producing carburizing atmospheres

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4049473A (en) * 1976-03-11 1977-09-20 Airco, Inc. Methods for carburizing steel parts
US4145232A (en) * 1977-06-03 1979-03-20 Union Carbide Corporation Process for carburizing steel
US5417774A (en) * 1992-12-22 1995-05-23 Air Products And Chemicals, Inc. Heat treating atmospheres

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US20030226620A1 (en) 2003-12-11
AU2003243343A1 (en) 2003-12-22

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