US3705058A - Soft-nitriding procedure for steel and cast iron - Google Patents

Soft-nitriding procedure for steel and cast iron Download PDF

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Publication number
US3705058A
US3705058A US160523A US3705058DA US3705058A US 3705058 A US3705058 A US 3705058A US 160523 A US160523 A US 160523A US 3705058D A US3705058D A US 3705058DA US 3705058 A US3705058 A US 3705058A
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Prior art keywords
steel
cast iron
soft
ammonia
procedure
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US160523A
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Zoltan Kolozsvari
Endre Gal
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FABRICA DE UTILAJE SI PIESE DE SCHIMB METALOTEHNICA
UTILAJE SI PIESE DE SCHIMB MET
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UTILAJE SI PIESE DE SCHIMB MET
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    • 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
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces

Definitions

  • Soft-nitriding of steel and cast iron machine parts is generally performed in a salt bath containing alcaline cyanides and cyanates.
  • the active carbon and nitrogen appears as a result of decomposition of the above salts.
  • the working temperature of the salt baths is of 570:10" C. (below of critical temperatures in Fe-N system).
  • a surface layer is to be obtained, composed of a compound (white) layer and a diffusion layer.
  • the compound layer is responsible for the high resistance to wear and scufiing, the diffusion layer forms a support.
  • a soft-nitriding procedure in a gaseous media is also known, using Endo-gas and ammonia. Backdraw of this procedure is the use of gas generator and a low nitriding potential.
  • the procedure in conformity with the invention eliminates the above disadvantages, performing the nitriding in order to realize a controlled and uniform treatment, at 570 i 10 C., in an atmopshere composed of ammonia, methane and oxygen.
  • the ammonia flow-rate has to be adjusted for a dissociation degree of 35-40%.
  • treating time can vary between 60 min. and 10 hours depending on parts to be treated and material.
  • a soft-nitriding procedure for increasing the nitrogen content of steel and cast iron articles comprising heat treating said articles for 1 to 10 hours at a temperature of 570 C. :10 C. in an atmosphere of ammonia, methane and oxygen while maintaining the dissociation rate of the ammonia between 38 and 40%, said atmosphere being characterized by having molar ratios of CH; to NH;, of 1 and CH,+NH to 0 of 25 to 30.

Abstract

A METHOD OF INCREASING THE NITROGEN CONTENT OF STEEL AND CAST IRON WHEREIN THE BODY IS MAINTAINED IN AN ATMOSPHERE OF AMMONIA, METHANE AND OXYGEN IN A MOLAR RATIO OF CH4:NH3=1 AND (CH4+NH3):O2=25-30 WHILE MAINTAINING THE DISSOCIATION RATE OF THE AMMONIA BETWEEN 38 AND 40%. THE TREATMENT TIME IS 1 TO 10 HOURS AT A TEMPERATURE OF 570* C.+ 10* C.

Description

United States Patent f 3,705,058 SOFT-NITRIDING PRQCEDURE FER STEEL AND CAST IRON Zoltan Kolozsvari and Endre Gal, Targu-Mures, Rumania, assignors to Fabrica de Utilaie si Piese de Schirnb Metalotehnica, Targu-Mures, Rurnania No Drawing. Filed July 7, 1971, Ser. No. 160,523 Claims priority, application Rumania, July 9, 1970,
6 Int. Cl. c236 11/16, 11/18 U.S. Cl. 148-16.6 1 Claim ABSTRACT OF THE DISCLOSURE A method of increasing the nitrogen content of steel and cast iron wherein the body is maintained in an atmosphere of ammonia, methane and oxygen in a molar ratio of CH :NH =1 and (CH,+NH ):O =25-30 while maintaining the dissociation rate of the ammonia between 38 and 40%. The treatment time is 1 to hours at a temperature of 570 C. :10 C.
SUMMARY As a result of the treatment a compound layer of a thickness of 10-15 m. is obtained, supported by a diffusion layer with a case depth depending on treating time and material composition.
The invention refers to a soft nitriding (low temperature carbonitriding) procedure of steel and cast iron in a controlled atmosphere.
Soft-nitriding of steel and cast iron machine parts is generally performed in a salt bath containing alcaline cyanides and cyanates. The active carbon and nitrogen appears as a result of decomposition of the above salts. The working temperature of the salt baths is of 570:10" C. (below of critical temperatures in Fe-N system). As result of the treatment a surface layer is to be obtained, composed of a compound (white) layer and a diffusion layer. The compound layer is responsible for the high resistance to wear and scufiing, the diffusion layer forms a support.
The above procedure presents disadvantages, because applying a salt bath with heavy toxic effect and by the other hand no continuous inspection and control of the bath characteristics is possible, the only inspection is by performing chemical analyses.
A soft-nitriding procedure in a gaseous media is also known, using Endo-gas and ammonia. Backdraw of this procedure is the use of gas generator and a low nitriding potential.
The procedure in conformity with the invention eliminates the above disadvantages, performing the nitriding in order to realize a controlled and uniform treatment, at 570 i 10 C., in an atmopshere composed of ammonia, methane and oxygen. The ratio of gas components is as Patented Dec. 5, 1972 follows: CH /NH =1 and (CH +NH )/O =25-30, with an ammonia dissociation rate of 384-0%, and a treating time of 1-10 hours.
An example of realizing the invention is given below, in order to soft-nitride pieces of OLC 35 (plain carbon steel with 0.35% C).
The treatment has been performed in a gaseous media of the following composition: NH /CH1,=1, adding oxygen in a ratio of CH NH /O =25-30, at a treating temperature of 570 :10 C. The ammonia flow-rate has to be adjusted for a dissociation degree of 35-40%.
A three hours treatment assures the following results:
Hardness Sample HB HVI HV3 HVfi HV1 HVt! Untreated 200-207 Nltrlded in salt bath 510 440 407 370 320 Gas-nitrided 490 430 400 380 340 Metallographic examination has shown the following data:
case depth (of diffusion layer): 0.350.40 mm. depth of compound layer: 10-15mm. microhardness of compound layer: 870-920 MHV.
On the basis of experiments the parameters of the above treatment, in conformity with the invention, have been established, as follows:
(a) temperature: 570 :10 C. (b) ratio of the components: NH /CH =1 and (CH-I-NHS (c) ammonia dissociation rate: 35-40% (d) treating time can vary between 60 min. and 10 hours depending on parts to be treated and material.
Advantages of the procedure in conformity with the invention are:
a clean metal surface can be obtained all the parameters of the procedure can be precisely checked and controlled.
What is claimed is:
1. A soft-nitriding procedure for increasing the nitrogen content of steel and cast iron articles, comprising heat treating said articles for 1 to 10 hours at a temperature of 570 C. :10 C. in an atmosphere of ammonia, methane and oxygen while maintaining the dissociation rate of the ammonia between 38 and 40%, said atmosphere being characterized by having molar ratios of CH; to NH;, of 1 and CH,+NH to 0 of 25 to 30.
References Cited UNITED STATES PATENTS 3,228,807 1/1966 Mitchell et al. 148-165 X 3,519,257 3/1968 Winter et al. 148-16'.5 X 3,620,518 11/1971 Winter et al. 148--16 3,399,085 8/1968 Knechtel et al. 148-16.6
FOREIGN PATENTS 125,006 Czechoslovakia.
48,847 Germany.
CHARLES N. LOVELL, Primary Examiner U.S. Cl. X.R 148-165
US160523A 1970-07-09 1971-07-07 Soft-nitriding procedure for steel and cast iron Expired - Lifetime US3705058A (en)

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RO6386470 1970-07-09

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DE (1) DE2133284C3 (en)
FR (1) FR2098281B1 (en)
GB (1) GB1351162A (en)
HU (1) HU163105B (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4035203A (en) * 1973-12-21 1977-07-12 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Method for the heat-treatment of steel and for the control of said treatment
US4049473A (en) * 1976-03-11 1977-09-20 Airco, Inc. Methods for carburizing steel parts
US4108693A (en) * 1974-12-19 1978-08-22 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Method for the heat-treatment of steel and for the control of said treatment
US4366008A (en) * 1979-02-09 1982-12-28 Kabushiki Kaisha Fujikoshi Method for hardening steel
US4386972A (en) * 1973-10-26 1983-06-07 Air Products And Chemicals, Inc. Method of heat treating ferrous metal articles under controlled furnace atmospheres
US20080000553A1 (en) * 2005-02-25 2008-01-03 Naoyuki Sano Soft-nitrided parts made of non-heat treated steel
US10094014B2 (en) * 2014-03-13 2018-10-09 Nippon Steel & Sumitomo Metal Corporation Nitriding method and nitrided part production method

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB395337A (en) * 1930-11-01 1933-07-13 Krupp Ag Improvements in processes for hardening iron, steel, and cast iron, alloys by nitrogenising

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4386972A (en) * 1973-10-26 1983-06-07 Air Products And Chemicals, Inc. Method of heat treating ferrous metal articles under controlled furnace atmospheres
US4035203A (en) * 1973-12-21 1977-07-12 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Method for the heat-treatment of steel and for the control of said treatment
US4108693A (en) * 1974-12-19 1978-08-22 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Method for the heat-treatment of steel and for the control of said treatment
US4049473A (en) * 1976-03-11 1977-09-20 Airco, Inc. Methods for carburizing steel parts
US4366008A (en) * 1979-02-09 1982-12-28 Kabushiki Kaisha Fujikoshi Method for hardening steel
US20080000553A1 (en) * 2005-02-25 2008-01-03 Naoyuki Sano Soft-nitrided parts made of non-heat treated steel
US10094014B2 (en) * 2014-03-13 2018-10-09 Nippon Steel & Sumitomo Metal Corporation Nitriding method and nitrided part production method

Also Published As

Publication number Publication date
DE2133284C3 (en) 1975-11-27
DE2133284A1 (en) 1972-02-24
FR2098281B1 (en) 1975-10-10
DE2133284B2 (en) 1975-04-24
FR2098281A1 (en) 1972-03-10
HU163105B (en) 1973-06-28
GB1351162A (en) 1974-04-24

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