EP0049530B1 - Procédé et dispositif pour carburer des pièces en acier - Google Patents

Procédé et dispositif pour carburer des pièces en acier Download PDF

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Publication number
EP0049530B1
EP0049530B1 EP81108034A EP81108034A EP0049530B1 EP 0049530 B1 EP0049530 B1 EP 0049530B1 EP 81108034 A EP81108034 A EP 81108034A EP 81108034 A EP81108034 A EP 81108034A EP 0049530 B1 EP0049530 B1 EP 0049530B1
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EP
European Patent Office
Prior art keywords
soot
workpieces
gas
annealing furnace
gas mixture
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
EP81108034A
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German (de)
English (en)
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EP0049530A1 (fr
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 EP0049530A1 publication Critical patent/EP0049530A1/fr
Application granted granted Critical
Publication of EP0049530B1 publication Critical patent/EP0049530B1/fr
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 and a device for case hardening metallic workpieces, in which the workpieces are brought to a high temperature in an annealing furnace, exposed to the action of a carbon-containing gas mixture and hardened.
  • gas carburizing and carbonitriding are becoming increasingly important.
  • the processes are carried out in closed-type annealing furnaces, which allow a controlled atmosphere to be set and maintained at a specific reaction temperature.
  • the main problem of the carburizing process is the transfer of carbon from the gas atmosphere to the material, e.g. B. steel, regulated to achieve reproducible carburization results on workpieces of different basic carbon content, different alloys and in particular different shapes.
  • hydrocarbons paraffin or paraffinic hydrocarbons, methane, ethane, propane, butane or natural gas with a proportion of 7.5 to 38 grams of carbon.
  • Oxygen, air, carbon dioxide, carbon monoxide, water vapor or mixtures thereof serve as oxygen donors.
  • the gas components are fed to the furnace separately or in mixtures.
  • the gas atmosphere is measured and controlled via a dew point, infrared (CO 2 ) or oxygen measurement.
  • the carburizing process is divided into two or three intervals in which the carburizing agent is fed into the furnace (interval carbons). The intervals are separated in time by two or three phases in which a carbonizing agent is fed into the furnace. During the carbonization intervals, the carbon potential in the furnace rises sharply and soot is formed. In the subsequent phase, in which air is fed into the furnace instead of carbon dioxide, the carbon potential drops again to 0. However, with this procedure, edge oxidation cannot be avoided. However, if the proportion of carburizing agent in the gas mixture is reduced in order to avoid excessive soot formation, the carburizing time increases considerably.
  • 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.
  • the invention has for its object to provide a method for evenly catching up workpieces that works more reliably and faster and thus more economically.
  • This object is achieved in that one or more of the carbon-containing gas components, the gas mixture during the action on the surface of the workpieces is or are added to the gas mixture while keeping other components of the gas mixture constant, such that the average carbon potential of the furnace atmosphere is always above the soot limit of the thermodynamic equilibrium, the duration of the addition period being short compared to the intermediate periods between two addition periods.
  • the invention is based on the knowledge that a large carbon potential gradient between the workpiece surface and the core itself comes to the fore as an additional driving diffusion force from the beginning of the carburization.
  • the carbon-containing gas components of the gas mixture are added in a pulsating manner. This means that the carbon content of the gas mixture is raised to a certain level in various phases during the carburization, these phases being separated by time intervals in which the carbon content is not changed by the addition of carbon-containing gas components, and the carbon content of the gas mixture consequently decreases.
  • the gas mixture has at least atmospheric pressure and rises rapidly during the intermittent addition of a carbon-containing gas component.
  • This pressure increase is particularly pronounced when hydrocarbons with two or more carbon atoms are introduced into the furnace, since each of their molecules breaks down into several gas molecules with a corresponding pressure increase.
  • the pressure of the gas atmosphere fluctuates in the same rhythm in which the pulsating addition of the carbon-containing gas components takes place (• breathing the gas atmosphere).
  • the main advantage of this process is that the glow time is reduced by up to 60% compared to the endogas process, whereby glow time is understood to mean the duration of carburization and diffusion. Large depths of hardening are also achieved. With the fiction According to the method, a uniform carburization is achieved, which leads to workpieces that are free of soot and edge oxidation. Furthermore, the process is significantly more reliable, because of the low H 2 content, the risk of explosion is lower and the furnaces can be gassed safely during idle and at the weekend. In addition, gas generators are no longer necessary.
  • the duration of the addition period being short compared to the spaces between two addition periods (diffusion phase).
  • the addition period is 2 to 200 seconds, preferably 15 to 60 seconds, while the duration of the diffusion phase is 10 to 500 seconds, preferably 50 to 200 seconds.
  • the methane and / or the soot content in the gas mixture is measured, the measured variables are fed to a control unit and the addition of one or more of the hydrocarbons by the control unit after comparison of the values of the methane and / or soot content with a setpoint set in each case.
  • the setpoints are selected so that over-carbonization, i.e. H. Soot formation does not take place.
  • the surface of the metallic workpieces therefore always remains soot-free. Rather, the carbon potential is kept almost constant at a value, the working line, around which the carbon potential fluctuates.
  • the carbon potential rises briefly during the pulse-like addition of hydrocarbons and falls below the almost constant mean value given during the subsequent diffusion phase. However, the carbon potential never drops to 0. It is crucial that the.
  • Working line of the process with a high carbon potential lies above the classic soot limit without producing soot, since the stay in the soot area is only very short. This fact has proven to be an essential feature of the method according to the invention, to which the high carburizing rate can be attributed.
  • the method according to the invention can also be used for carbonitriding the workpieces.
  • ammonia is added pulsating to the gas mixture while it is acting on the surface of the workpieces.
  • An annealing furnace for carrying out the method according to the invention essentially has a device for supplying and discharging gases into or from the annealing furnace, a gas analyzer for determining the methane content in the gas atmosphere and an associated control device.
  • the control device is advantageously connected to a soot sensor, the control unit being responsive to the difference between measured value signals and a setpoint signal for the soot and / or methane content which can be set in one or two setpoint transmitters and being connected to a valve for the addition of hydrocarbons.
  • the device for supplying the carbon-containing gas components opens into the interior of the annealing furnace in the lower region and in the immediate vicinity of the workpieces to be carburized in the annealing furnace.
  • An annealing furnace 1 is connected via a line 2 to a control unit consisting of a soot sensor 3, a gas analyzer 4 and a controller 5.
  • the gas components nitrogen, carbon dioxide and hydrocarbon, which come directly from storage bottles, are fed via valves 7, 8 and 9 and a feed 6 into the annealing furnace, which is connected to an exhaust line 10 for the exhaust gases.
  • Valve 7, which regulates the supply of nitrogen is open for driving in and heating up the batch in the furnace chamber, while valve 8 (carbon dioxide) and valve 9 (hydrocarbon, for example propane) are closed.
  • valves 7 and 8 are open and also valve 9, for a short time, for example 20 seconds.
  • the gas mixture passed into the furnace chamber accordingly consists of inert nitrogen, CO 2 and propane.
  • the propane is unstable at the high temperatures and breaks down into radicals, some of which are highly reactive, which cause rapid oversaturation of the workpiece surface with carbon. Because of the resulting significant carbon potential gradient between the workpiece surface and the core, this potential gradient comes to the fore as an additional driving diffusion force from the beginning of the carbonization.
  • both methane and soot are generated in the gas mixture.
  • a portion of this gas mixture is withdrawn via line 2 and the soot content in the soot sensor and the methane content in the gas analyzer 4, for example an infrared analyzer, are measured.
  • the controller 5 the output values of these two measuring devices are compared with predetermined target values and the valve 9 is closed via a relay 11 when these target values are exceeded thus the supply of z.
  • the addition period for the propane is, for example, 20 seconds.
  • the controller 5 opens the valve 9 again via the relay 11 and a new cycle begins.
  • valves 8 and 9 close and the charge is lowered to the hardening temperature.
  • a double spur gear made of 20 Mn Cr S , module 5 is sketched in the detail in FIG. 3.
  • the broad dashed line outside the body edges marks the surface hardened area, the narrow dashed line its position and its course.
  • the course of the hardened surface layer requires the determination of the measuring points, designated M1 and M2, for the hardening depth.
  • a production batch with a surface area of approximately 11 m 2 and a weight of approximately 500 kg is carburized in an Aichelin multi-purpose chamber furnace for 130 minutes at an annealing temperature of 945 ° C.
  • the addition period for propane is about 20 seconds and the duration of the diffusion phase is about 60 seconds.
  • Figure 4 shows the hardness curve on a double spur gear (material 16 Mn Cr s ) from this batch again.
  • the surface hardness in HV according to DIN 6773 is plotted against the hardening depth in mm.
  • Curve 1 relates to measuring point 1 and curve 2 to measuring point 2.
  • the workpiece is free of carbides and residual austenite, the carburized steel is martensite. It can clearly be seen that there is constant surface hardening down to a hardening depth of approx. 0.45 mm. However, this then decreases with the hardening depth, due to the shape of the workpiece at measuring point M1 more slowly than at measuring point M2.
  • a specified surface hardness of 610 HV (solid line) corresponds to a hardening depth of 0.83 mm at measuring point M1 and 0.68 mm at measuring point M2. This means that the indentation in the workpiece is hardened enough to avoid deformation.
  • Example 2 Analogous to Example 1, with the difference that the annealing temperature is 960 ° C., the annealing time is 30 minutes, the addition period for propane is 90 seconds on average and the diffusion time is approximately 200 seconds.
  • Figure 5 shows the hardness curve.
  • a surface hardness of 610 HV corresponds to a hardening depth of 0.45 mm at measuring point M1 and 0.36 mm at measuring point M2. So after a short time (30 min) a considerable hardening depth was reached.
  • FIG. 6 shows the course of the case hardening depth at a limit hardness of 610 HV1 as a function of the annealing time at different annealing temperatures.
  • the almost linear course of the curve from a hardening depth of approx. 0.45 mm is noteworthy.
  • Curves for annealing temperatures between 930 ° C and 960 ° C lie between the two curves shown. The results of 60 tests under production conditions are incorporated into the curve.

Claims (9)

1. Procédé pour la cémentation de pièces métalliques, dans lequel les pièces sont portées à températures élevées dans un four de recuit, sont soumises à l'action d'un mélange gazeux contenant du carbone et sont durcies, caractérisé en ce qu'un ou plusieurs des composants gazeux du mélange gazeux contenant du carbone, sont ajoutés au mélange gazeux pendant son action sur la surface des pièces, de façon pulsée et en maintenant constants d'autres composants du mélange gazeux de telle sorte que le potentiel de carbone moyen de l'atmosphère gazeuse soit constamment situé au-dessus de la limite de formation de suie de l'équilibre thermodynamique, la durée de la période d'addition étant courte par rapport aux intervalles de temps existant entre deux périodes d'addition.
2. Procédé selon la revendication 1, caractérisé en ce qu'un ou plusieurs hydrocarbures sont ajoutés de façon pulsée.
3. Procédé selon la revendication 2, caractérisé en ce que des hydrocarbures contenant deux atomes de carbone ou plus sont ajoutés de façon pulsée.
4. Procédé selon une des revendications 1 à 3, caractérisé en ce que la période d'addition est de 2 à 200 secondes et en ce que le temps s'écoulant depuis la fin d'une période d'addition jusqu'au début de la période suivante (phase de diffusion) s'élève de 10 à 500 secondes.
5. Procédé selon une des revendications 1 à 4, caractérisé en ce que la période d'addition est de 15 à 60 secondes et en ce que le temps s'écoulant depuis la fin d'une période d'addition jusqu'au début de la suivante est de 50 à 200 secondes.
6. Procédé selon une des revendications 1 à 5, caractérisé en ce que, de façon continue, la teneur en méthane et/ou la teneur en suie sont mesurées dans le mélange gazeux, les grandeurs de mesure sont appliquées à une unité de régulation et l'addition d'un ou de plusieurs des hydrocarbures est réglée par l'unité de régulation après comparaison des valeurs de la teneur en méthane et/ou de la teneur en suie avec une valeur de consigne respectivement prédéterminée.
7. Procédé selon une des revendications 1 à 6, caractérisé en ce que de l'ammoniac est addition- nellement ajouté de façon pulsée au mélange pendant son action sur la surface des pièces.
8. Four de recuit pour la mise en oeuvre du procédé selon une des revendications 1 à 7, comportant des dispositifs pour assurer l'admission et la décharge de gaz par rapport au volume intérieur du four de recuit, un analyseur de gaz pour la détermination de la teneur en méthane dans l'atmosphère gazeuse et un dispositif de régulation associée, caractérisé en ce que le dispositif de régulation est relié à un détecteur de suie, et le dispositif de régulation réagit à la différence entre des signaux de valeur de mesure et un signal de valeur de consigne de la teneur en suie et/ou de la teneur en méthane, pouvant être réglé dans un ou deux générateurs de valeur de consigne, et est en liaison avec une vanne pour l'admission de composants gazeux contenant du carbone.
9. Four de recuit selon la revendication 8, caractérisé en ce que le dispositif d'admission des composants gazeux contenant du carbone débouche dans le volume intérieur du four de recuit dans une zone inférieure et au voisinage immédiat des pièces à carburer se trouvant dans le four.
EP81108034A 1980-10-08 1981-10-07 Procédé et dispositif pour carburer des pièces en acier Expired EP0049530B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19803038078 DE3038078A1 (de) 1980-10-08 1980-10-08 Verfahren und vorrichtung zum aufkohlen metallischer werkstuecke
DE3038078 1980-10-08

Publications (2)

Publication Number Publication Date
EP0049530A1 EP0049530A1 (fr) 1982-04-14
EP0049530B1 true EP0049530B1 (fr) 1985-06-05

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EP81108034A Expired EP0049530B1 (fr) 1980-10-08 1981-10-07 Procédé et dispositif pour carburer des pièces en acier

Country Status (11)

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US (1) US4472209A (fr)
EP (1) EP0049530B1 (fr)
AT (1) AT369792B (fr)
AU (1) AU543782B2 (fr)
BR (1) BR8102150A (fr)
DE (2) DE3038078A1 (fr)
DK (1) DK433181A (fr)
ES (1) ES8206658A1 (fr)
GR (2) GR75086B (fr)
NO (1) NO813283L (fr)
ZA (1) ZA812500B (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3714283C1 (de) * 1987-04-29 1988-11-24 Ipsen Ind Internat Gmbh Verfahren zur Gasaufkohlung von Stahl
DE4221958C1 (de) * 1992-07-02 1993-11-18 Mannesmann Ag Verfahren zum Herstellen eines Zahnradelementes einer Ritzelwelle
DE10232432A1 (de) * 2002-07-17 2004-01-29 Linde Ag Verfahren und Vorrichtung zum Unterdruckaufkohlen
DE102007047074A1 (de) * 2007-10-01 2009-04-02 Robert Bosch Gmbh Verfahren zur Aufkohlung von Werkstücken sowie Verwendung

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DE3146042A1 (de) * 1981-11-20 1983-05-26 Linde Ag, 6200 Wiesbaden Verfahren zum einsatzhaerten metallischer werkstuecke
DE3411605C2 (de) * 1984-03-29 1986-07-17 Joachim Dr.-Ing. 7250 Leonberg Wünning Verfahren und Einrichtung zur Gasaufkohlung von Stahl
DE3507527A1 (de) * 1984-11-20 1986-05-22 Ewald 4133 Neukirchen-Vluyn Schwing Verfahren und anlage zum aufkohlen eines werkstueckes aus stahl
US4632707A (en) * 1985-04-09 1986-12-30 Air Products And Chemicals, Inc. Protective atmosphere process for annealing and/or hardening ferrous metals
WO1992005295A1 (fr) * 1986-08-12 1992-04-02 Nobuo Nishioka Procede et appareil de cementation au gaz
DE3707003A1 (de) * 1987-03-05 1988-09-15 Ewald Schwing Verfahren zum aufkohlen eines werkstueckes aus stahl
US4776901A (en) * 1987-03-30 1988-10-11 Teledyne Industries, Inc. Nitrocarburizing and nitriding process for hardening ferrous surfaces
US4989840A (en) * 1989-11-08 1991-02-05 Union Carbide Canada Limited Controlling high humidity atmospheres in furnace main body
CH681186A5 (fr) * 1989-11-09 1993-01-29 Battelle Memorial Institute
US5133813A (en) * 1990-07-03 1992-07-28 Tokyo Heat Treating Company Ltd. Gas-carburizing process and apparatus
FR2678287B1 (fr) * 1991-06-26 1993-10-29 Etudes Constructions Mecaniques Procede et four de cementation a basse pression.
FR2681332B1 (fr) * 1991-09-13 1994-06-10 Innovatique Sa Procede et dispositif de cementation d'un acier dans une atmosphere a basse pression.
IT1272670B (it) * 1993-09-24 1997-06-26 Lindberg Ind Srl Metodo e dispositivo per la formazione e l'erogazione controllata di un'atmosfera gassosa ad almeno due componenti ed applicazione di impianti di trattamento termico o di combustibile
RU2048601C1 (ru) * 1993-12-20 1995-11-20 Рыжов Николай Михайлович Способ диагностики процесса химико-термической обработки сталей и сплавов в тлеющем разряде и устройство для его осуществления
FR2821362B1 (fr) * 2001-02-23 2003-06-13 Etudes Const Mecaniques Procede de cementation basse pression
US7468107B2 (en) * 2002-05-01 2008-12-23 General Motors Corporation Carburizing method
DE10221605A1 (de) * 2002-05-15 2003-12-04 Linde Ag Verfahren und Vorrichtung zur Wärmebehandlung metallischer Werkstücke
DE10235131A1 (de) * 2002-08-01 2004-02-19 Ipsen International Gmbh Verfahren und Vorrichtung zum Schwärzen von Bauteilen
WO2005038076A1 (fr) * 2003-10-14 2005-04-28 Etudes Et Constructions Mecaniques Procede et four de cementation basse pression
EP2541179A3 (fr) * 2005-11-23 2014-09-24 Surface Combustion, Inc. Générateur de gaz pour le traitement de surface d' articles métalliques dans un four atmosphérique
US20080120843A1 (en) * 2006-11-06 2008-05-29 Gm Global Technology Operations, Inc. Method for manufacturing low distortion carburized gears
US8075420B2 (en) * 2009-06-24 2011-12-13 Acushnet Company Hardened golf club head
DE112010005929A5 (de) 2010-10-11 2014-01-02 Ipsen International Gmbh Verfahren und Einrichtung zum Aufkohlen und Carbonitrieren von metallischen Werkstoffen

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3714283C1 (de) * 1987-04-29 1988-11-24 Ipsen Ind Internat Gmbh Verfahren zur Gasaufkohlung von Stahl
DE4221958C1 (de) * 1992-07-02 1993-11-18 Mannesmann Ag Verfahren zum Herstellen eines Zahnradelementes einer Ritzelwelle
DE10232432A1 (de) * 2002-07-17 2004-01-29 Linde Ag Verfahren und Vorrichtung zum Unterdruckaufkohlen
DE102007047074A1 (de) * 2007-10-01 2009-04-02 Robert Bosch Gmbh Verfahren zur Aufkohlung von Werkstücken sowie Verwendung

Also Published As

Publication number Publication date
EP0049530A1 (fr) 1982-04-14
BR8102150A (pt) 1982-08-17
AT369792B (de) 1983-01-25
ATA539980A (de) 1982-06-15
ES505891A0 (es) 1982-09-01
AU543782B2 (en) 1985-05-02
ES8206658A1 (es) 1982-09-01
DE3170866D1 (en) 1985-07-11
DE3038078A1 (de) 1982-05-06
NO813283L (no) 1982-04-13
US4472209A (en) 1984-09-18
AU6915481A (en) 1982-04-22
ZA812500B (en) 1982-04-28
GR75086B (fr) 1984-07-13
DK433181A (da) 1982-04-09
GR75375B (fr) 1984-07-13

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