EP0049531B1 - Verfahren zum Einsatzhärten metallischer Werkstücke - Google Patents

Verfahren zum Einsatzhärten metallischer Werkstücke Download PDF

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Publication number
EP0049531B1
EP0049531B1 EP81108035A EP81108035A EP0049531B1 EP 0049531 B1 EP0049531 B1 EP 0049531B1 EP 81108035 A EP81108035 A EP 81108035A EP 81108035 A EP81108035 A EP 81108035A EP 0049531 B1 EP0049531 B1 EP 0049531B1
Authority
EP
European Patent Office
Prior art keywords
gas
pressure fluctuations
furnace
carbon
components
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
EP81108035A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0049531A1 (de
Inventor
Karlheinz Längerich
Rüdiger Dr. Conrad
Wolfgang Dr. Danzer
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.)
Linde GmbH
Original Assignee
Linde GmbH
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 Linde GmbH filed Critical Linde GmbH
Publication of EP0049531A1 publication Critical patent/EP0049531A1/de
Application granted granted Critical
Publication of EP0049531B1 publication Critical patent/EP0049531B1/de
Expired legal-status Critical Current

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

Definitions

  • the invention relates to a method for case hardening metallic workpieces, in which they are exposed in a furnace at high temperatures to the action of a carbon-containing gas atmosphere in which pressure fluctuations are generated.
  • Case hardening is a process for the heat treatment of metals in the presence of a carbon-containing or nitrogen-containing gas mixture, in which the surface layer of a metal workpiece is thermochemically treated with carbon and, if necessary, with nitrogen (carburizing or carbonitriding).
  • the heat treatment changes the chemical composition of the workpiece by diffusing carbon or nitrogen in or out.
  • the transport of the gaseous carburizing agent to the workpiece can be the rate-determining step of the carburizing process in the case of rapidly carburizing gas atmospheres.
  • the transport of the gaseous carburizing agent to the workpiece can be the rate-determining step of the carburizing process in the case of rapidly carburizing gas atmospheres.
  • GB-A-527 081 discloses a method for carburizing.
  • a gas mixture is prepared outside a furnace, compressed to a pressure above ambient pressure and then expanded into the furnace interior. The pressure increase inside the furnace is reduced by leaks in the furnace.
  • a process for case hardening is known from DE-B-1 041 067, in which pressure fluctuations are generated in the gas atmosphere within a furnace.
  • Hardening technology notices Vol. 35 (1980) No. 5, pages 230 to 237, disclose the use of a treatment gas for case hardening, which is composed of gases containing carbon, nitrogen and oxygen. From hardening technology communications, Vol. 35 (1980) No. 6, pages 284 to 288, it is known for thermochemical treatment to regulate the composition of the furnace atmosphere by measuring the residual methane content or the oxygen partial pressure.
  • the carburizing agent for example methane
  • the carburizing agent is added in two or three time intervals, which are interrupted by breaks in which no carburizing agent is added and the diffusion of the carbon or nitrogen into the edge area of the metallic workpiece takes place. In relation to the time period of the heat treatment, these intervals last relatively long (a few minutes up to approx. 1 hour).
  • the invention is therefore based on the object of specifying a method of the type described in the introduction, in which a uniform surface quality of all treated metallic workpieces is achieved by the heat treatment.
  • This object is achieved in that the gas atmosphere is formed from at least two components and the pressure fluctuations are generated by pulsating the addition of at least two components with different amplitudes and frequencies of the pressure fluctuations of the individual gas components in the furnace.
  • gas movement is forced by constant pressure changes during the heat treatment process of the entire gas atmosphere and thus also in the vicinity of geometrically unfavorable metal parts. Due to the pressure changes, a largely homogeneous gas atmosphere is established in all furnace areas.
  • the carburizing agent or the carbonitriding agent is therefore transported to the workpiece uniformly and sufficiently quickly at all points on the workpiece to be treated, so that the carbon potential has almost the same value at all points on the workpiece surface during the carburizing process. Insufficient carburization of disadvantaged workpiece surfaces or excessive carburization of favored workpiece surfaces is therefore avoided.
  • edge zone properties of the workpieces treated by the method according to the invention therefore improve since it is not necessary to add oxygen to remove the soot deposits.
  • the method according to the invention also shortens the entire carburizing process, since a large carbon potential gradient is achieved between the workpiece surface and the workpiece core and this potential gradient also acts as a driving diffusion force.
  • the gas mixture is composed of an inert carrier gas, a carbon- and nitrogen-containing gas and a oxygen-containing gas formed.
  • the pressure fluctuations are generated by pulsating admixing of two gas components to the third gas component or by pulsating mixing of all gas components.
  • the pressure fluctuations of the inert carrier gas can be dimensioned such that a constant gas movement which is dependent on the furnace size, among other things, is brought about within the furnace, while the pressure fluctuations of the carbon-containing or nitrogen-containing gas are primarily aimed at the carbon or carbide required for case hardening. Provide sufficient nitrogen.
  • the period of the pressure fluctuations is advantageously shorter compared to the duration of the heat treatment.
  • the method according to the invention is particularly useful when the furnace atmosphere outside the furnace is formed from two or more components, which are stored individually and mixed under excess pressure and input into the furnace.
  • each individual gas component can be mixed with the other components in a pulsating manner.
  • only one shut-off device is required, which can be operated automatically if necessary.
  • a hydrocarbon with more than one carbon atom is advantageously used as the carbon-containing gas in the process according to the invention.
  • Such hydrocarbons become unstable at the temperatures prevailing in the furnace and break down into several gaseous radicals. Because of the constant furnace volume, the decay results in a pressure increase, which is higher the more radicals are formed. This effect is superimposed on the pressure fluctuations caused by the pulsating addition and amplifies these fluctuations.
  • the frequency of the pressure fluctuations is set as a function of the methane and / or hydrogen and / or soot content in the furnace atmosphere.
  • the method according to the invention not only achieves a faster carburization but also an improved carburization - in particular at geometrically unfavorable points.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Making Paper Articles (AREA)
  • Threshing Machine Elements (AREA)
EP81108035A 1980-10-08 1981-10-07 Verfahren zum Einsatzhärten metallischer Werkstücke Expired EP0049531B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3038082 1980-10-08
DE19803038082 DE3038082A1 (de) 1980-10-08 1980-10-08 Verfahren zum einsatzhaerten metallischer werkstuecke

Publications (2)

Publication Number Publication Date
EP0049531A1 EP0049531A1 (de) 1982-04-14
EP0049531B1 true EP0049531B1 (de) 1985-06-05

Family

ID=6113954

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81108035A Expired EP0049531B1 (de) 1980-10-08 1981-10-07 Verfahren zum Einsatzhärten metallischer Werkstücke

Country Status (9)

Country Link
EP (1) EP0049531B1 (da)
AT (1) ATA539780A (da)
AU (1) AU542462B2 (da)
BR (1) BR8102151A (da)
DE (2) DE3038082A1 (da)
DK (1) DK433081A (da)
ES (1) ES8206641A1 (da)
NO (1) NO813284L (da)
ZA (1) ZA812499B (da)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3146042A1 (de) * 1981-11-20 1983-05-26 Linde Ag, 6200 Wiesbaden Verfahren zum einsatzhaerten metallischer werkstuecke
FR2586259B1 (fr) * 1985-08-14 1987-10-30 Air Liquide Procede de cementation rapide dans un four continu

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE618026C (de) * 1932-08-28 1935-08-30 Ewald Hanus Verfahren zum Zementieren von Eisen und Stahl
FR835931A (fr) * 1938-03-30 1939-01-05 Procédé pour la cémentation gazeuse de pièces en acier
DE1041067B (de) * 1955-12-06 1958-10-16 Elino Ind Ofenbau Carl Hanf & Verfahren zum Aufkohlen, Nitrieren oder Karbonitrieren von Stahlteilen
DE2624828C2 (de) * 1976-06-03 1985-08-14 Alco Standard Corp., Valley Forge Verfahren und Ofen zur Durchführung einer Wärmebehandlung von Werkstücken
DE2851982A1 (de) * 1978-12-01 1980-06-12 Degussa Verfahren zum steuern von aufkohlungsprozessen im unterdruckbereich

Also Published As

Publication number Publication date
ES505892A0 (es) 1982-09-01
DK433081A (da) 1982-04-09
DE3170867D1 (en) 1985-07-11
EP0049531A1 (de) 1982-04-14
AU6915581A (en) 1982-04-22
ES8206641A1 (es) 1982-09-01
NO813284L (no) 1982-04-13
BR8102151A (pt) 1982-08-17
AU542462B2 (en) 1985-02-21
DE3038082A1 (de) 1982-05-06
ZA812499B (en) 1982-04-28
ATA539780A (de) 1982-04-15

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