GB1575342A - Production of furnace atmospheres for the heat treatment of ferrous metals - Google Patents

Production of furnace atmospheres for the heat treatment of ferrous metals Download PDF

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Publication number
GB1575342A
GB1575342A GB17609/77A GB1760977A GB1575342A GB 1575342 A GB1575342 A GB 1575342A GB 17609/77 A GB17609/77 A GB 17609/77A GB 1760977 A GB1760977 A GB 1760977A GB 1575342 A GB1575342 A GB 1575342A
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GB
United Kingdom
Prior art keywords
furnace chamber
hydrocarbon
moles
carbon
oxygen
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.)
Expired
Application number
GB17609/77A
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.)
Air Products and Chemicals Inc
Original Assignee
Air Products and Chemicals 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
Application filed by Air Products and Chemicals Inc filed Critical Air Products and Chemicals Inc
Priority to GB17609/77A priority Critical patent/GB1575342A/en
Priority to FR7812463A priority patent/FR2388896A2/en
Priority to DE19782818558 priority patent/DE2818558A1/en
Priority to ZA00782403A priority patent/ZA782403B/en
Publication of GB1575342A publication Critical patent/GB1575342A/en
Expired 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
    • 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
    • C23C8/28—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 more than one element being applied in one step
    • C23C8/30—Carbo-nitriding
    • C23C8/32—Carbo-nitriding of ferrous surfaces

Description

(54) IMPROVEMENTS RELATING TO THE PRODUCTION OF FURNACE ATMOSPHERES FOR THE HEAT TREATMENT OF FERROUS METALS (71) We. AIR PRODUCTS AND CHEMICALS INC., a company organised under the laws of the State of Delaware, United States of America, of P.O. Box 538, Allentown, Pennsylvania 18105, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, to be particularly described in and by the following statement: In our U.K. Patent Specification No.
1,471,880, we have described a method of heat treating ferrous metal in a furnace chamber which method comprises the steps of mixing an oxygen bearing medium selected from the group oxygen, air, carbon dioxide, carbon monoxide, water vapour and mixtures thereof; hydrocarbon; and an inert gas carrier to produce a gaseous mixture each 100 gm moles of which comprises between 2 and 7.4 gm moles oxygen (either as gaseous oxygen or in the form of carbon dioxide, carbon monoxide, water vapour and mixtures thereof); between 60 and 95 gm moles inert gas; and between a trace and 38 gm moles hydrocarbon containing 7.5 to 38 gm atoms of carbon (the number of gm atoms of carbon in the hydrocarbon being greater than the number of gm moles of oxygen in the oxgyen bearing medium), and delivering said mixture to said furnace chamber which is maintained at or above 690"C and wherein the mixture reacts to form a carbon controlled atmosphere.
We now believe that, although it is highly desirable to premix the oxygen bearing medium, hydrocarbon and inert gas carrier before they are introduced into the furnace chamber, this is not absolutely essential.
Accordingly, the present invention provides a method of heat treating ferrous metal in a furnace chamber which method comprises the steps of introducing into said furnace chamber an oxygen bearing medium selected from the group oxygen, air, carbon dioxide, carbon monoxide, water vapour and mixtures thereof; hydrocarbon; and an inert gas carrier; in a manner such that each 100 gm moles entering said furnace chamber comprises between 2 and 7.4 moles- oxygen (either as gaseous oxygen or in the form of carbon dioxide, carbon monoxide, water vapour and mixtures thereof); between 60 and 95 gm moles of inert gas; and between a trace and 38 gm moles hydrocarbon containing 7.5 to 38 gm atoms of carbon (the number of gm atoms of carbon in the hydrocarbon being greater than the number of gm moles oxygen in the oxygen bearing medium); and wherein said furnace chamber is maintained at or above 690"C and wherein the oxygen bearing medium, hydrocarbon and inert gas carrier form (within the furnace chamber) a mixture which reacts to form a carbon controlled atmosphere.
Preferably, the oxygen bearing medium hydrocarbon and inert gas carrier are delivered to the furnace chamber through respective separate and distinct inlets.
It is also possible for the oxygen bearing medium and inert gas carrier to be premixed and introduced into the furnace chamber through a separate and distinct inlet from the inlet for the hydrocarbon.
Alternatively, the hydrocarbon can be premixed with the inert gas carrier and introduced into the furnace chamber through a separate and distinct inlet from the oxygen.
Although not recommended, the hydrocarbon and oxygen could be premixed and introduced into the furnace chamber through a separate and distinct inlet from the inert gas carrier.
Preferably, the carbon potential is controlled by adjusting the volume ratio of hydrocarbon to oxygen bearing medium.
The inert gas carrier is preferably nitrogen.
Advantageously. each 100 gm moles en tering the furnace chamber contains between 70 and 95 gm moles nitrogen and --more preferably between 89 and 95 gm moles nitrogen.
Pr;eferably the hydrocarbon is a paraffin; methane, ethane, butane and propane being particularly suitable.
Each 100 gm moles entering the furnace chamber preferably contain between a trace and 19.4 gm moles of hydrocarbon containing 7.5 to 19.4 gm atoms of carbon and more preferably between a trace and 12.7 gm moles of hydrocarbon containing 7.75 to 12.7 gm atoms of carbon.
If desired - the mixture .may be supplemented by a volume 'of ammonia to perform carbonitriding. The volume of ammonia to (ammonia plus mixture) is preferably less than or equal to 1:5 (by volume).
Advantageously the flows of the oxygen bearing medium, hydrocarbon and inert gas carrier are adjusted so that the carbon controlled atmosphere within the furnace chamber contains between 3.9 and 10.7% (by volume) carbon, monoxide and more preferably between 3.9 and 8.2% thereof.
Although not. essential, the oxygen bear- ing medium, hydrocarbon and inert gas are preferably introduced into the furnace chamber in the immediate vicinity of the or one of the fans which:islused to circulate the atmosphere in the furnace chamber.
For a better understanding. of the present invention, - reference will now be made, by way of example, to the accompanying drawing, which shows a schematic vertical cross section.through a furnace chamber for the heat treatment of metal.
Referring to the drawing, there is shown a furnace chamber for the.heat treatment of metal. The furnace chamber is generally identified by reference numeral 1 and includes a door 2, a circulating fan 3, an exhaust vent 4 and separate and distinct inlets 5, 6, 7-and 8. In use for carburizing, furnace chamber 1 is heated to about 800"C by radiant tubes 9. A stream of nitrogen is then introduced into the furnace chamber 1 through inlet 5.
When the nitrogen has displaced substantially all the air in the furnace chamber 1, circulating fan 3 is started and propane and carbon dioxide are admitted through inlets 6 and 7 respectively. The flow of propane, carbon dioxide and nitrogen is then adjusted to give the furnace chamber the appropriate carbon potential. Suitable mixtures of nitrogen, propane and carbon dioxide are described in our aforementioned Patent Specification.
The articles to be carburized are placed on trays which are introduced into furnace chamber 1 through door 2.
After subjecting the articles to the required atmosphere(s), temperature(s) and time, the articles are removed from the furnace chamber 1.
It should be noted that the inlets 5, 6, 7 and 8 - are situated closely adjacent the rotational axis of the circulating fan 3 which ensures that adequate mixing occurs.
Inlet 8 is used for the introduction of ammonia when the furnace chamber is used for carbonitriding as described in our aforementioned Patent Specification.
WHAT WE CLAIM IS: 1. A method of heat treating ferrous metal in a furnace chamber which method comprises the steps of introducing into said furnace chamber an oxygen bearing medium selected from the group oxygen, air, carbon dioxide, carbon monoxide, water vapour and mixtures thereof; hydrocarbon; and an inert gas carrier; in a manner such that each 100 gm moles entering said furnace chamber comprises between 2 and 7.4 gm moles oxygen (either as gaseous oxygen or in jthe form of carbon dioxide, carbon monoxide, water vapour and mixtures thereof); between 60 and 95 gm moles of inert gas; and between a trace and 38 gm moles hydrocarbon coritaining 7.5 to 38 gm atoms of carbon (the number of gm atoms of carbon in the hydrocarbon being greater'than the number of gm moles oxygen in the oxygen bearing medium); and wherein said furnace chamber is maintained at or above 690"C and wherein the oxygen bearing medium, hydrocarbon and inert gas carrier form (within the furnace chamber) a mixture which reacts to form a carbon controlled atmosphere.
2. A method as claimed in Claim 1, wherein the oxygen bearing medium, hydrocarbon and inert gas carrier are delivered to the furnace chamber through respective separate and distinct inlets.
3. A method as claimed in Claim 1 wherein the oxygen bearing medium and inert gas carrier are premixed and introduced into the furnace chamber through a separate and distinct inlet from the inlet for the hydrocarbon.
4. A method as claimed in Claim 1, wherein the hydrocarbon is premixed with the inert gas carrier and introduced-into the furnace chamber through a separate and distinct inlet from the oxygen.
5. A method as claimed- in Claim 1, wherein the hydrocarbon and oxygen are premixed and introduced into the furnace chamber through a separate and distinct inlet from the inert gas carrier.
6. A method as claimed in any preceding claim, wherein each 100 gm moles entering the furnace chamber contains between 70 and 95 gm moles nitrogen.
7. A method as claimed in any preceding claim wherein the hydrocarbon is a paraffin.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. tering the furnace chamber contains between 70 and 95 gm moles nitrogen and --more preferably between 89 and 95 gm moles nitrogen. Pr;eferably the hydrocarbon is a paraffin; methane, ethane, butane and propane being particularly suitable. Each 100 gm moles entering the furnace chamber preferably contain between a trace and 19.4 gm moles of hydrocarbon containing 7.5 to 19.4 gm atoms of carbon and more preferably between a trace and 12.7 gm moles of hydrocarbon containing 7.75 to 12.7 gm atoms of carbon. If desired - the mixture .may be supplemented by a volume 'of ammonia to perform carbonitriding. The volume of ammonia to (ammonia plus mixture) is preferably less than or equal to 1:5 (by volume). Advantageously the flows of the oxygen bearing medium, hydrocarbon and inert gas carrier are adjusted so that the carbon controlled atmosphere within the furnace chamber contains between 3.9 and 10.7% (by volume) carbon, monoxide and more preferably between 3.9 and 8.2% thereof. Although not. essential, the oxygen bear- ing medium, hydrocarbon and inert gas are preferably introduced into the furnace chamber in the immediate vicinity of the or one of the fans which:islused to circulate the atmosphere in the furnace chamber. For a better understanding. of the present invention, - reference will now be made, by way of example, to the accompanying drawing, which shows a schematic vertical cross section.through a furnace chamber for the heat treatment of metal. Referring to the drawing, there is shown a furnace chamber for the.heat treatment of metal. The furnace chamber is generally identified by reference numeral 1 and includes a door 2, a circulating fan 3, an exhaust vent 4 and separate and distinct inlets 5, 6, 7-and 8. In use for carburizing, furnace chamber 1 is heated to about 800"C by radiant tubes 9. A stream of nitrogen is then introduced into the furnace chamber 1 through inlet 5. When the nitrogen has displaced substantially all the air in the furnace chamber 1, circulating fan 3 is started and propane and carbon dioxide are admitted through inlets 6 and 7 respectively. The flow of propane, carbon dioxide and nitrogen is then adjusted to give the furnace chamber the appropriate carbon potential. Suitable mixtures of nitrogen, propane and carbon dioxide are described in our aforementioned Patent Specification. The articles to be carburized are placed on trays which are introduced into furnace chamber 1 through door 2. After subjecting the articles to the required atmosphere(s), temperature(s) and time, the articles are removed from the furnace chamber 1. It should be noted that the inlets 5, 6, 7 and 8 - are situated closely adjacent the rotational axis of the circulating fan 3 which ensures that adequate mixing occurs. Inlet 8 is used for the introduction of ammonia when the furnace chamber is used for carbonitriding as described in our aforementioned Patent Specification. WHAT WE CLAIM IS:
1. A method of heat treating ferrous metal in a furnace chamber which method comprises the steps of introducing into said furnace chamber an oxygen bearing medium selected from the group oxygen, air, carbon dioxide, carbon monoxide, water vapour and mixtures thereof; hydrocarbon; and an inert gas carrier; in a manner such that each 100 gm moles entering said furnace chamber comprises between 2 and 7.4 gm moles oxygen (either as gaseous oxygen or in jthe form of carbon dioxide, carbon monoxide, water vapour and mixtures thereof); between 60 and 95 gm moles of inert gas; and between a trace and 38 gm moles hydrocarbon coritaining 7.5 to 38 gm atoms of carbon (the number of gm atoms of carbon in the hydrocarbon being greater'than the number of gm moles oxygen in the oxygen bearing medium); and wherein said furnace chamber is maintained at or above 690"C and wherein the oxygen bearing medium, hydrocarbon and inert gas carrier form (within the furnace chamber) a mixture which reacts to form a carbon controlled atmosphere.
2. A method as claimed in Claim 1, wherein the oxygen bearing medium, hydrocarbon and inert gas carrier are delivered to the furnace chamber through respective separate and distinct inlets.
3. A method as claimed in Claim 1 wherein the oxygen bearing medium and inert gas carrier are premixed and introduced into the furnace chamber through a separate and distinct inlet from the inlet for the hydrocarbon.
4. A method as claimed in Claim 1, wherein the hydrocarbon is premixed with the inert gas carrier and introduced-into the furnace chamber through a separate and distinct inlet from the oxygen.
5. A method as claimed- in Claim 1, wherein the hydrocarbon and oxygen are premixed and introduced into the furnace chamber through a separate and distinct inlet from the inert gas carrier.
6. A method as claimed in any preceding claim, wherein each 100 gm moles entering the furnace chamber contains between 70 and 95 gm moles nitrogen.
7. A method as claimed in any preceding claim wherein the hydrocarbon is a paraffin.
8. A method as claimed in any preceding
claim wherein each 100 gm moles entering the furnace chamber contains between a trace and 19.4 gm moles of hydrocarbon containing 7.5 to 19.4 gm atoms of carbon.
9. A method as claimed in any preceding claim wherein said mixture is supplemented by a volume of ammonia such that the volume of ammonia to (ammonia plus mixture) is less than or equal to 1:5 (by volume).
10. A method as claimed in any preceding claim wherein the flows of the oxygen bearing medium, hydrocarbon and inert gas carrier are adjusted so that the carbon controlled atmosphere within the furnace chamber contains between 3.9 and 10.7 % (by volume) carbon monoxide.
11. A method as claimed in any preceding claim wherein the oxygen bearing medium, hydrocarbon and inert gas are introduced into the furnace chamber in the immediate vicinity of the or one of the fans which is used to circulate the atmosphere in the furnace chamber.
12. A method of heat treating ferrous metal in a furnace chamber substantially as herein described with reference to the accompanying drawing.
GB17609/77A 1977-04-27 1977-04-27 Production of furnace atmospheres for the heat treatment of ferrous metals Expired GB1575342A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB17609/77A GB1575342A (en) 1977-04-27 1977-04-27 Production of furnace atmospheres for the heat treatment of ferrous metals
FR7812463A FR2388896A2 (en) 1977-04-27 1978-04-27 THERMAL TREATMENT PROCESS OF FERROUS METALS
DE19782818558 DE2818558A1 (en) 1977-04-27 1978-04-27 METHOD FOR THE HEAT TREATMENT OF FERROUS METALS
ZA00782403A ZA782403B (en) 1977-04-27 1978-04-27 Improvements relating to the production of furnace atmospheres for the heat treatments of ferrous metals

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB17609/77A GB1575342A (en) 1977-04-27 1977-04-27 Production of furnace atmospheres for the heat treatment of ferrous metals

Publications (1)

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GB1575342A true GB1575342A (en) 1980-09-17

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DE (1) DE2818558A1 (en)
FR (1) FR2388896A2 (en)
GB (1) GB1575342A (en)
ZA (1) ZA782403B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT376703B (en) * 1982-08-18 1984-12-27 Linde Ag METHOD FOR PRODUCING A NITROGEN AND HYDROGEN-CONTAINING GAS ATMOSPHERES FOR THE GLOWING OF METAL WORKPIECES AND APPLICATION OF THE METHOD

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2446322A2 (en) 1979-01-15 1980-08-08 Air Liquide METHOD FOR HEAT TREATMENT OF STEEL AND CONTROL OF SAID TREATMENT
DE3038078A1 (en) * 1980-10-08 1982-05-06 Linde Ag, 6200 Wiesbaden METHOD AND DEVICE FOR CARBONING METAL WORKPIECES
FR2524006B1 (en) * 1982-03-23 1985-10-11 Air Liquide PROCESS FOR THE SURFACE CURING OF METAL PARTS

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1150079A (en) * 1956-04-26 1958-01-07 Renault Process for preparing atmosphere for heat treatment of metals
CH448673A (en) * 1965-12-09 1967-12-15 Four Electr Delemont Sa Du Gas carburizing process of steel
GB1471880A (en) * 1973-10-26 1977-04-27 Air Prod & Chem Furnace atmosphere for the heat treatment of ferrous metal
JPS5178714A (en) * 1974-12-28 1976-07-08 Kobe Steel Ltd Kofunmatsutaino kanetsuhoho
US4049473A (en) * 1976-03-11 1977-09-20 Airco, Inc. Methods for carburizing steel parts

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT376703B (en) * 1982-08-18 1984-12-27 Linde Ag METHOD FOR PRODUCING A NITROGEN AND HYDROGEN-CONTAINING GAS ATMOSPHERES FOR THE GLOWING OF METAL WORKPIECES AND APPLICATION OF THE METHOD

Also Published As

Publication number Publication date
ZA782403B (en) 1979-06-27
FR2388896B2 (en) 1981-01-09
FR2388896A2 (en) 1978-11-24
DE2818558A1 (en) 1978-11-09

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