EP0779376A1 - Plasma carburizing of metallic workpieces - Google Patents
Plasma carburizing of metallic workpieces Download PDFInfo
- Publication number
- EP0779376A1 EP0779376A1 EP96118592A EP96118592A EP0779376A1 EP 0779376 A1 EP0779376 A1 EP 0779376A1 EP 96118592 A EP96118592 A EP 96118592A EP 96118592 A EP96118592 A EP 96118592A EP 0779376 A1 EP0779376 A1 EP 0779376A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- propane
- methane
- carbon
- plasma
- 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.)
- Granted
Links
- 238000005255 carburizing Methods 0.000 title claims description 21
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 36
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000001294 propane Substances 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 238000000034 method Methods 0.000 claims description 24
- 239000007789 gas Substances 0.000 claims description 7
- DPQUFPIZKSPOIF-UHFFFAOYSA-N methane propane Chemical compound C.CCC.CCC DPQUFPIZKSPOIF-UHFFFAOYSA-N 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 abstract description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 4
- 150000001721 carbon Chemical class 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 239000004071 soot Substances 0.000 description 2
- 229910001149 41xx steel Inorganic materials 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Images
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
- C23C8/36—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 using ionised gases, e.g. ionitriding
- C23C8/38—Treatment of ferrous surfaces
Definitions
- the invention relates to a process for the plasma carburization of metallic workpieces in a furnace, the furnace atmosphere containing a carbon carrier which is split under the process conditions of the plasma carburization with the release of pure carbon.
- propane (C 3 H 8 ) is generally used as the carbon carrier, which is split in the course of the so-called propane pyrolysis according to the following reaction equations: C. 3rd H 8th ⁇ CH 4th + C 2nd H 4th C. 2nd H 4th ⁇ 2C + 2H 2nd CH 4th ⁇ C + 2H 2nd
- methane (CH 4 ) is mostly used as the carbon carrier, which is obtained by methane pyrolysis according to the equation CH 4th ⁇ C + 2H 2nd is split.
- propane instead of methane.
- propane is a more effective carbon carrier than methane due to its larger number of carbon atoms - 3 carbon atoms for propane versus 1 carbon atom for methane.
- propane has the disadvantage that propane is thermally split in the temperature range above 600 ° C., as a result of which carburization takes place in the furnace, which leads to sooting of the furnace.
- Methane on the other hand, has only one carbon atom, but the methane molecule is so stable that it is not already split at the necessary carburizing temperature. Rather, the splitting takes place only in the plasma and therefore really only on the workpiece surface. Since the carbon mass flow density is only very low when splitting methane, large-scale batches are very difficult to carburize evenly with methane.
- the invention has for its object to provide a method for the plasma carburizing of metal workpieces, which ensures carburizing with a high carbon mass flow density, without at the same time the risk of sooting the furnace.
- the achievement of the high carbon mass flow density on the one hand and the avoidance of sooting on the other hand is due to the fact that propane can provide much more carbon than methane due to its three carbon atoms during thermal and electrical splitting in the plasma.
- the methane on the other hand hardly splits at carburizing temperatures between 800 ° C and 1000 ° C.
- the methane is only split in the plasma, ie really only on the workpiece surface, so that these released carbon atoms can only contribute to carburizing the workpieces, but not to sooting the furnace.
- the gas pressure in the furnace atmosphere is below 10 mbar, since thermal splitting of the methane is almost impossible in this pressure range.
- the furnace atmosphere can also contain other gases, in particular hydrogen and / or argon, which, as inert gases, are also intended to prevent oxidation of the workpieces.
- the drawing shows the hardness curve for the material 27 CrMo 4 according to the plasma carburizing process with a methane-propane mixture as a carbon carrier.
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)
- Arc Welding In General (AREA)
Abstract
Description
Die Erfindung betrifft ein Verfahren zur Plasmaaufkohlung metallischer Werkstücke in einem Ofen, wobei die Ofenatmosphäre einen Kohlenstoff-Träger enthält, der unter den Prozeßbedingungen der Plasmaaufkohlung unter Abgabe von reinem Kohlenstoff gespalten wird.The invention relates to a process for the plasma carburization of metallic workpieces in a furnace, the furnace atmosphere containing a carbon carrier which is split under the process conditions of the plasma carburization with the release of pure carbon.
Unter den thermochemischen Behandlungsverfahren zur Einsatzhärtung metallischer Werkstücke haben sich in den letzten Jahren neben der konventionellen Gasaufkohlung immer mehr die Aufkohlungsprozesse in Vakuumanlagen durchgesetzt, da nur mit diesen Verfahren eine randoxidationsfreie Aufkohlung realisierbar ist. Bei diesen Aufkohlungsprozessen in Vakuumanlagen handelt es sich um die Niederdruck- und die Plasmaaufkohlung. Da bei diesen Aufkohlungsverfahren ohne sauerstoffhaltige Reaktionsgase gearbeitet wird, kann keine C-Pegelregelung erfolgen; die entscheidende Kenngröße für den Kohlenstoffübergang ist bei diesen Verfahren die Kohlenstoff-Massenstromdichte, die als Kohlenstoffmenge definiert ist, die pro Zeit- und Flächeneinheit in den Werkstoff übergeht. Dieser zur Aufkohlung benötigte Kohlenstoff wird von einem in der Ofenatmosphäre befindlichen Kohlenstoff-Träger - meist einem Kohlenwasserstoff - zur Verfügung gestellt, der bei den gegebenen Prozeßbedingungen unter Abgabe von reinem Kohlenstoff gespalten wird.In addition to conventional gas carburizing, the carburizing processes in vacuum systems have become more and more common among thermochemical treatment processes for case hardening of metallic workpieces, since only these processes can be used to carry out carburizing without edge oxidation. These carburizing processes in vacuum plants are low pressure and plasma carburizing. Since these carburizing processes work without oxygen-containing reaction gases, no C level control can take place; The decisive parameter for the carbon transition in these processes is the carbon mass flow density, which is defined as the amount of carbon that passes into the material per unit of time and area. This carbon required for the carburization is made available by a carbon carrier in the furnace atmosphere - usually a hydrocarbon - which is split under the given process conditions with the release of pure carbon.
Bei den bekannten Niederdruck-Aufkohlungsverfahren wird als Kohlenstoff-Träger in der Regel Propan (C3H8) verwendet, welches im Laufe der sogenannten Propanpyrolyse nach folgenden Reaktionsgleichungen gespalten wird:
Bei der Plasmaaufkohlung wird als Kohlenstoff-Träger meist Methan (CH4) verwendet, welches im Wege der Methanpyrolyse nach der Gleichung
Die Verwendung von Methan oder Propan als Kohlenstoff-Träger ist jeweils mit verschiedenen Vor- und Nachteilen verbunden. So ist beispielsweise Propan aufgrund seiner größeren Anzahl von Kohlenstoffatomen - 3 C-Atome beim Propan gegenüber 1 C-Atom beim Methan - ein wirksamerer Kohlenstoff-Träger als Methan. Andererseits weist Propan jedoch den Nachteil auf, daß Propan bereits im Temperaturbereich über 600°C thermisch gespalten wird, wodurch bereits im Ofen eine Aufkohlung stattfindet, die zum Verrußen des Ofens führt. Methan hingegen weist zwar nur ein C-Atom auf, jedoch ist das Methan-Molekül so stabil, daß es nicht bereits bei der notwendigen Aufkohlungstemperatur gespalten wird. Die Spaltung erfolgt vielmehr erst im Plasma und somit wirklich nur an der Werkstückoberfläche. Da die Kohlenstoff-Massenstromdichte bei der Spaltung von Methan nur sehr gering ist, lassen sich großflächige Chargen nur sehr schwer gleichmäßig mit Methan aufkohlen.The use of methane or propane as a carbon carrier has various advantages and disadvantages. For example, propane is a more effective carbon carrier than methane due to its larger number of carbon atoms - 3 carbon atoms for propane versus 1 carbon atom for methane. On the other hand, however, propane has the disadvantage that propane is thermally split in the temperature range above 600 ° C., as a result of which carburization takes place in the furnace, which leads to sooting of the furnace. Methane, on the other hand, has only one carbon atom, but the methane molecule is so stable that it is not already split at the necessary carburizing temperature. Rather, the splitting takes place only in the plasma and therefore really only on the workpiece surface. Since the carbon mass flow density is only very low when splitting methane, large-scale batches are very difficult to carburize evenly with methane.
In Anbetracht des voranstehend geschilderten Standes der Technik liegt der Erfindung die Aufgabe zugrunde, ein Verfahren zur Plasmaaufkohlung metallischer Werkstücke bereitzustellen, das eine Aufkohlung mit einer hohen Kohlenstoff-Massenstromdichte gewährleistet, ohne daß gleichzeitig die Gefahr der Verrußung des Ofens besteht.In view of the prior art described above, the invention has for its object to provide a method for the plasma carburizing of metal workpieces, which ensures carburizing with a high carbon mass flow density, without at the same time the risk of sooting the furnace.
Überraschenderweise hat sich im Laufe der Versuche herausgestellt, daß diese Aufgabe erfindungsgemäß dadurch gelöst wird, daß als Kohlenstoff-Träger ein Gemisch aus Methan und Propan verwendet wird.Surprisingly, the experiments has been found in the course that this object is inventively achieved in that a mixture of methane and propane is used as carbon support.
Das Erreichen der hohen Kohlenstoff-Massenstromdichte einerseits und das Vermeiden der Verrußung des Ofens andererseits kommt dabei dadurch zustande, daß Propan aufgrund seiner drei C-Atome bei der thermischen und elektrischen Spaltung im Plasma viel mehr Kohlenstoff zur Verfügung stellen kann als Methan. Das Methan auf der anderen Seite spaltet sich bei den Aufkohlungstemperaturen zwischen 800°C und 1000°C fast gar nicht. Die Spaltung des Methans findet erst im Plasma, also wirklich nur an der Werkstückoberfläche statt, so daß diese frei werdenden Kohlenstoff-Atome nur zum Aufkohlen der Werkstücke, nicht jedoch zur Verrußung des Ofens beitragen können.The achievement of the high carbon mass flow density on the one hand and the avoidance of sooting on the other hand is due to the fact that propane can provide much more carbon than methane due to its three carbon atoms during thermal and electrical splitting in the plasma. The methane on the other hand hardly splits at carburizing temperatures between 800 ° C and 1000 ° C. The methane is only split in the plasma, ie really only on the workpiece surface, so that these released carbon atoms can only contribute to carburizing the workpieces, but not to sooting the furnace.
Bei den Versuchen hat sich herausgestellt, daß ein Methan-Propan-Gemisch mit bis zu 60 Vol.-% Propan, insbesondere einem Propan-Anteil von 5 bis 50 Vol.-% besonders geeignet ist, um ohne Rußbildung eine hohe Kohlenstoff-Massenstromdichte bzw. Kohlenstoff-Übertragungsrate zu erhalten.The tests have shown that a methane / propane mixture with up to 60 vol.% Propane, in particular a propane fraction of 5 to 50 vol.%, Is particularly suitable for achieving a high carbon mass flow density or soot formation without soot formation To get carbon transfer rate.
Gemäß einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens beträgt der Gasdruck in der Ofenatmosphäre unter 10 mbar, da in diesem Druckbereich eine thermische Spaltung des Methans nahezu unmöglich ist.According to a preferred embodiment of the method according to the invention, the gas pressure in the furnace atmosphere is below 10 mbar, since thermal splitting of the methane is almost impossible in this pressure range.
Neben dem Methan-Propan-Gemisch kann die Ofenatmosphäre zusätzlich noch weitere Gase, insbesondere Wasserstoff und/oder Argon enthalten, welche als Inertgase zusätzlich die Oxidation der Werkstücke verhindern sollen.In addition to the methane-propane mixture, the furnace atmosphere can also contain other gases, in particular hydrogen and / or argon, which, as inert gases, are also intended to prevent oxidation of the workpieces.
In der Zeichnung ist für den Werkstoff 27 CrMo 4 der Härteverlauf nach dem Plasmaaufkohlungsverfahren mit einem Methan-Propan-Gemisch als Kohlenstoff-Träger dargestellt.The drawing shows the hardness curve for the material 27 CrMo 4 according to the plasma carburizing process with a methane-propane mixture as a carbon carrier.
Die Prozeßparameter für den in der Abbildung dargestellten Plasmaaufkohlungsprozeß waren:
- zehnminütiges Aufkohlen bei einer Aufkohlungstemperatur von 940°C.
- Die anschließende Diffusionsphase betrug 51 Minuten,
- woran anschließend nach dem Absenken auf die Härtetemperatur von 860°C die Charge mittels Hochdruckgasabschreckung abgeschreckt wurde.
- carburizing for ten minutes at a carburizing temperature of 940 ° C.
- The subsequent diffusion phase was 51 minutes,
- after which the charge was quenched by high-pressure gas quenching after lowering to the hardening temperature of 860 ° C.
Als Ergebnis dieses Prozesses wurde eine Einsatzhärtungstiefe (550 HV 1) von 0,7 mm auf der Zahnflanke erzielt.As a result of this process, a case hardening depth (550 HV 1) of 0.7 mm was achieved on the tooth flank.
Mit dem voranstehend dargestellten Verfahren ist es somit möglich, durch die Verwendung des Methan-Propan-Gemisches als Kohlenstoff-Träger die Kohlenstoff-Massenstromdichte bei der Plasmaaufkohlung deutlich zu erhöhen, ohne daß die Gefahr der Verrußung des Ofens besteht.With the method described above, it is thus possible, by using the methane-propane mixture as the carbon carrier, to significantly increase the carbon mass flow density in the plasma carburizing, without the risk of sooting the furnace.
Claims (6)
dadurch gekennzeichnet,
daß als Kohlenstoff-Träger ein Gemisch aus Methan und Propan verwendet wird.Process for plasma carburizing metallic workpieces in a furnace, the furnace atmosphere containing a carbon carrier which is split under the process conditions of plasma carburization with the release of pure carbon,
characterized,
that a mixture of methane and propane is used as the carbon carrier.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19547131 | 1995-12-16 | ||
DE19547131A DE19547131A1 (en) | 1995-12-16 | 1995-12-16 | Process for plasma carburizing metallic workpieces |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0779376A1 true EP0779376A1 (en) | 1997-06-18 |
EP0779376B1 EP0779376B1 (en) | 2000-01-26 |
EP0779376B2 EP0779376B2 (en) | 2002-12-18 |
Family
ID=7780384
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96118592A Expired - Lifetime EP0779376B2 (en) | 1995-12-16 | 1996-11-20 | Plasma carburizing of metallic workpieces |
Country Status (4)
Country | Link |
---|---|
US (1) | US5851314A (en) |
EP (1) | EP0779376B2 (en) |
AT (1) | ATE189271T1 (en) |
DE (2) | DE19547131A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19815233A1 (en) * | 1998-04-04 | 1999-10-07 | Ald Vacuum Techn Gmbh | Process for vacuum carburizing under treatment gas |
WO2008025344A1 (en) * | 2006-08-31 | 2008-03-06 | Schaeffler Kg | Process for producing a highly case-hardenable roller bearing component |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050016831A1 (en) * | 2003-07-24 | 2005-01-27 | Paganessi Joseph E. | Generation of acetylene for on-site use in carburization and other processes |
DE102004053935B4 (en) * | 2004-11-09 | 2015-04-09 | Schaeffler Technologies AG & Co. KG | Process for the heat treatment of a component made of a thermosetting heat-resistant steel and a component made of a thermosetting, heat-resistant steel |
KR101622306B1 (en) * | 2009-10-29 | 2016-05-19 | 삼성전자주식회사 | Graphene sheet, substrate comprising graphene sheet and process for preparing these materials |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58113371A (en) * | 1981-12-28 | 1983-07-06 | Seiko Epson Corp | Plasma surface hardening method |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5139584A (en) † | 1989-07-13 | 1992-08-18 | Solo Fours Industriels Sa | Carburization process |
US5383980A (en) * | 1992-01-20 | 1995-01-24 | Leybold Durferrit Gmbh | Process for hardening workpieces in a pulsed plasma discharge |
DE4427902C1 (en) * | 1994-08-06 | 1995-03-30 | Leybold Durferrit Gmbh | Method for carburising components made from carburisable materials by means of a plasma discharge operated in a pulsed fashion |
-
1995
- 1995-12-16 DE DE19547131A patent/DE19547131A1/en not_active Withdrawn
-
1996
- 1996-11-20 AT AT96118592T patent/ATE189271T1/en not_active IP Right Cessation
- 1996-11-20 EP EP96118592A patent/EP0779376B2/en not_active Expired - Lifetime
- 1996-11-20 DE DE59604291T patent/DE59604291D1/en not_active Expired - Fee Related
- 1996-12-13 US US08/766,282 patent/US5851314A/en not_active Expired - Fee Related
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58113371A (en) * | 1981-12-28 | 1983-07-06 | Seiko Epson Corp | Plasma surface hardening method |
Non-Patent Citations (4)
Title |
---|
CHEMICAL ABSTRACTS, vol. 102, no. 26, 1 July 1985, Columbus, Ohio, US; abstract no. 224092u, SGIBNEV V.V.: "machine experiment study of mechanisms of processes occuring in a glow discharge in a medium of hydrocarbons" page 212; XP002028317 * |
FIZ. KHIM. OBRAB. MATER., vol. 2, no. 75-8, 1985, OMSK,SU * |
HOFFMANN F ET AL: "ASPEKTE DES UNTERDRUCK- UND PLASMAAUFKOHLENS", HAERTEREI TECHNISCHE MITTEILUNGEN, vol. 49, no. 2, 1 March 1994 (1994-03-01), pages 103 - 111, XP000436013 * |
PATENT ABSTRACTS OF JAPAN vol. 7, no. 219 (C - 188) 29 September 1983 (1983-09-29) * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19815233A1 (en) * | 1998-04-04 | 1999-10-07 | Ald Vacuum Techn Gmbh | Process for vacuum carburizing under treatment gas |
WO2008025344A1 (en) * | 2006-08-31 | 2008-03-06 | Schaeffler Kg | Process for producing a highly case-hardenable roller bearing component |
Also Published As
Publication number | Publication date |
---|---|
DE19547131A1 (en) | 1997-06-19 |
ATE189271T1 (en) | 2000-02-15 |
US5851314A (en) | 1998-12-22 |
DE59604291D1 (en) | 2000-03-02 |
EP0779376B2 (en) | 2002-12-18 |
EP0779376B1 (en) | 2000-01-26 |
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