EP0670375A1 - Method of hardening of metal valves, in particular intake valves for internal combustion engines - Google Patents

Method of hardening of metal valves, in particular intake valves for internal combustion engines Download PDF

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Publication number
EP0670375A1
EP0670375A1 EP95101756A EP95101756A EP0670375A1 EP 0670375 A1 EP0670375 A1 EP 0670375A1 EP 95101756 A EP95101756 A EP 95101756A EP 95101756 A EP95101756 A EP 95101756A EP 0670375 A1 EP0670375 A1 EP 0670375A1
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EP
European Patent Office
Prior art keywords
valves
hardening
valve
internal combustion
combustion engines
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
Application number
EP95101756A
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German (de)
French (fr)
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EP0670375B1 (en
Inventor
Hora Dipl.-Ing. Pavel
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Mercedes Benz Group AG
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Daimler Benz AG
Mercedes Benz AG
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Publication of EP0670375A1 publication Critical patent/EP0670375A1/en
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Expired - Lifetime legal-status Critical Current

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    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
    • F01L3/02—Selecting particular materials for valve-members or valve-seats; Valve-members or valve-seats composed of two or more materials

Definitions

  • the invention relates to a method for hardening single-metal valves according to the preamble of patent claim 1.
  • Single-metal inlet valves in particular those made of hardenable steel X 45 CrSi 9 3, are today usually treated at the various function points such as the shaft end, keyway, shaft and valve seat with locally targeted, different hardening processes, which can only be carried out in time-consuming individual hardenings, which have to be carried out separately for each function point can be carried out.
  • This is known for example from DE-PS 40 14 072.
  • Different locally different hardening levels for intake valves are also known from DE-AS 14 76 045, but only for steels with a proportion of 0.08 to 0.25% carbon. Due to the different individual hardenings, the hardening of such inlet valves is very expensive.
  • valve stem The end of the stem and the keyway as well as the valve seat are locally hardened by separate induction processes, whereas the valve stem is nitrided either with a low hardening depth or hardened on the surface by galvanic chrome plating to form a bi-metal valve.
  • the object of the invention is to develop a method for hardening mono-material valves which is inexpensive but nevertheless ensures sufficient hardness and crack resistance in all functional areas of the valves, in particular in the stem area.
  • the separate individual hardening performed for locally different areas on the valve can be dispensed with, as a result of which time is saved in production and the apparatus equipment specially designed and therefore expensive for each individual hardening is eliminated. Furthermore, a uniform mass hardening is made possible, in which the valves hardened in this way have sufficient hardness and crack resistance at all functional points, the latter in particular in the valve stem area.
  • the hardening method according to the invention is based on the knowledge that years of observations of damage cases are based on the fact that a toughness of the material, due to the hardening process, is not essential for the durability of the valve, especially in the stem area. Brittle fractures only occur with chrome-plated valves (bi-metal valves) and are caused by hydrogen embrittlement that occurs during galvanic chrome plating. By contrast, the furnace hardening used in the invention precludes the introduction of hydrogen into the valve material.
  • the shaft hardness offers good wear protection and increases the resistance to plastic deformation of the valve when overloaded during operation.
  • the valves can be hardened as bulk material in an expedient manner, which saves a time-consuming, separate installation of the valves.
  • FIG. 1 to 4 show individual stages of the valve shape in the manufacturing process of a valve for internal combustion engines, in particular for intake valves.
  • a rod material blank 1 shown in FIG. 1 made of a hardenable steel such as X 45 CrSi 9 3 is heated at one end 2.
  • a pear 3 (FIG. 2) is then compressed by electric upsetting, after which the blank 1 is forged into a valve 4.
  • the valve stem 5 and the valve plate 6 are preformed (FIG. 3). 4
  • the valve 4 is possibly machined, whereby the stem end 7 and the valve plate 6 are functionally designed and a keyway 8 is machined into the valve stem 5 in the region of the end 7.
  • the method of hot extrusion is also conceivable for its production.
  • the material in bar form is heated to the forming temperature and pressed through a die with a negative shape of the valve.
  • valves 4 designed in this way are received for hardening as bulk material 10 in a basket 11 and introduced into a hardening furnace 12 with the latter.
  • the valves are in the hardening furnace 12 4 evenly and simultaneously heat-treated at a temperature of about 950 ° C for a period of 1-2 hours and normal atmosphere and then quenched together from the furnace heat in an oil bath 13, whereby this is heated to about 100 ° C (Fig. 5).
  • Fig. 5 In the furnace heat, all surface parts and component cross sections of the valves 4 are treated uniformly and thus the individual functional valve sections such as the valve stem 5, the valve plate 6, the shaft end 7, the keyway 8 and the valve plate bottom 9 are heat treated in the same way.
  • the quenched valves 4 are then pushed into a further furnace 14 in the basket 11 and there subjected to the relaxation annealing process at a temperature of approximately 200 ⁇ 20 ° C. for about 1 ⁇ 2 - 1 hour.
  • a temperature of approximately 200 ⁇ 20 ° C. for about 1 ⁇ 2 - 1 hour As a result, residual stress peaks in the structure that arise during hardening are reduced and, at the same time, a structural transformation of tetragonal plate marten sites into cubic martensite is achieved. This improves the toughness of the valve material and levels different hardnesses between the valves 4. These are adjusted to a hardness in the range of 57 ⁇ 3 HRC. 6 shows the cut hatch 15, a machined, uniformly and uniformly hardened single valve 4.
  • valves 4 are finished by grinding or polishing to produce the required surface quality.

Abstract

Uni-metallic valves, esp. alloyed steel inlet valves for internal combustion engines, undergo martensitic age-hardening using a process involving annealing at approximately 950[deg]C, quenching, then tempering at 200+-20[deg]C, resulting in a hardness of 57+-3 HRC.

Description

Die Erfindung betrifft ein verfahren zum Härten von Einmetall-Ventilen gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a method for hardening single-metal valves according to the preamble of patent claim 1.

Einmetall-Einlaßventile, insbesondere solche aus einem härtbaren Stahl X 45 CrSi 9 3 werden heute üblicherweise an den verschiedenen Funktionsstellen wie Schaftende, Keilnut, Schaft und Ventilsitz mit örtlich gezielt wirkenden unterschiedlichen Härteverfahren behandelt, was nur in zeitraubenden, für jede Funktionsstelle zeitversetzt gesondert vorzunehmenden Einzelhärtungen durchgeführt werden kann. Dies ist beispielsweise aus der DE-PS 40 14 072 bekannt. Verschiedene lokal unterschiedlich wirkende Härtungsstufen für Einlaßventile sind auch aus der DE-AS 14 76 045, jedoch nur für Stähle mit einem Anteil von 0,08 bis 0,25% Kohlenstoff bekannt. Aufgrund der verschiedenen Einzelhärtungen gestaltet sich das Härten von derartigen Einlaßventilen sehr kostspielig. Das Schaftende und die Keilnut sowie der Ventilsitz werden durch gesonderte Induktionsverfahren örtlich gezielt gehärtet, wogegen der Ventilschaft entweder bei geringer Einhärtetiefe nitriergehärtet oder oberflächlich durch galvanisches Aufchromen unter Bildung eines Bi-Metall-Ventiles hart gemacht wird.Single-metal inlet valves, in particular those made of hardenable steel X 45 CrSi 9 3, are today usually treated at the various function points such as the shaft end, keyway, shaft and valve seat with locally targeted, different hardening processes, which can only be carried out in time-consuming individual hardenings, which have to be carried out separately for each function point can be carried out. This is known for example from DE-PS 40 14 072. Different locally different hardening levels for intake valves are also known from DE-AS 14 76 045, but only for steels with a proportion of 0.08 to 0.25% carbon. Due to the different individual hardenings, the hardening of such inlet valves is very expensive. The end of the stem and the keyway as well as the valve seat are locally hardened by separate induction processes, whereas the valve stem is nitrided either with a low hardening depth or hardened on the surface by galvanic chrome plating to form a bi-metal valve.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum Härten von Mono-Werkstoff-Ventilen zu entwickeln, das preisgünstig ist, jedoch gleichwohl eine in allen Funktionsbereichen der Ventile ausreichende Härte und Rißbeständigkeit, insbesondere im Schaftbereich gewährleistet.The object of the invention is to develop a method for hardening mono-material valves which is inexpensive but nevertheless ensures sufficient hardness and crack resistance in all functional areas of the valves, in particular in the stem area.

Die Aufgabe ist erfindungsgemäß durch die im Patentanspruch 1 angegebenen kennzeichnenden Merkmale gelöst.The object is achieved by the characterizing features specified in claim 1.

Dank der Erfindung kann auf die für lokal unterschiedlichen Bereiche am Ventil vorgenommenen, gesonderten Einzelhärtungen verzichtet werden, wodurch Zeit in der Fertigung eingespart wird und die für jede Einzelhärtung speziell ausgebildete und daher teuere apparative Ausrüstung entfällt. Desweiteren wird eine einheitliche Massenhärtung ermöglicht, bei der die derart gehärteten Ventile an sämtlichen Funktionsstellen eine ausreichende Härte und Rißbeständigkeit, letztere insbesondere im Ventilschaftbereich aufweisen.Thanks to the invention, the separate individual hardening performed for locally different areas on the valve can be dispensed with, as a result of which time is saved in production and the apparatus equipment specially designed and therefore expensive for each individual hardening is eliminated. Furthermore, a uniform mass hardening is made possible, in which the valves hardened in this way have sufficient hardness and crack resistance at all functional points, the latter in particular in the valve stem area.

Dem erfindungsgemäßen Härtungsverfahren liegt die auf jahrelange Beobachtungen von Schadensfällen sich stützende Erkenntnis zugrunde, daß eine - härtungsbedingt geringe - Zähigkeit des Werkstoffes, gerade im Schaftbereich für die Haltbarkeit des Ventils nicht von wesentlicher Bedeutung ist. Sprödbrüche treten dabei nur bei verchromten Ventilen (Bi-Metall-Ventilen) auf und werden infolge einer beim galvanischen Verchromen einsetzende Wasserstoffversprödung verursacht. Durch die in der Erfindung verwandte Ofenhärtung ist dementgegen ein Wasserstoffeintrag in den Ventilwerkstoff ausgeschlossen.The hardening method according to the invention is based on the knowledge that years of observations of damage cases are based on the fact that a toughness of the material, due to the hardening process, is not essential for the durability of the valve, especially in the stem area. Brittle fractures only occur with chrome-plated valves (bi-metal valves) and are caused by hydrogen embrittlement that occurs during galvanic chrome plating. By contrast, the furnace hardening used in the invention precludes the introduction of hydrogen into the valve material.

Darüber hinaus bietet die Schafthärte einen guten Verschleißschutz und erhöht den Widerstand gegen plastische Verformungen des Ventils bei Überlastung im Betrieb. Gemäß des Unteranspruches 2 können die Ventile in zweckmäßiger Weise als Schüttgut gehärtet werden, wodurch eine zeitraubende voneinander getrennte Aufstellung der Ventile erspart wird.In addition, the shaft hardness offers good wear protection and increases the resistance to plastic deformation of the valve when overloaded during operation. According to dependent claim 2, the valves can be hardened as bulk material in an expedient manner, which saves a time-consuming, separate installation of the valves.

In der nachfolgenden Zeichnungsbeschreibung wird ein Ausführungsbeispiel der Erfindung näher erläutert; dabei zeigen:

  • Fig. 1 einen Stangenmaterialrohling in einer Seitenansicht,
  • Fig. 2 den Rohling aus Fig. 1 nach einer Stauchbehandlung in einer Seitenansicht,
  • Fig. 3 der gestauchte Rohling aus Fig. 2 in ausgeschmiedeter Ventilform in einer Seitenansicht,
  • Fig. 4 das Ventil aus Fig. 3 nach zerspanender Bearbeitung,
  • Fig. 5 eine schematisierte Härtung mehrerer Ventile gemäß Fig. 3,
  • Fig. 6 ein Einzelventil im einheitlich durchgehärteten Zustand nach Entspannungsglühen aus Fig. 5 in einem Längsschnitt.
In the following description of the drawings, an embodiment of the invention is explained in more detail; show:
  • 1 shows a rod material blank in a side view,
  • 2 shows the blank from FIG. 1 after a compression treatment in a side view,
  • 3 the upset blank from FIG. 2 in a forged valve shape in a side view,
  • 4 shows the valve from FIG. 3 after machining,
  • 5 shows a schematic hardening of several valves according to FIG. 3,
  • 6 shows a single valve in the uniformly fully hardened state after stress relief annealing from FIG. 5 in a longitudinal section.

In Fig. 1 bis 4 sind einzelne Stufen der Ventilform im Herstellungsprozeß eines Ventils für Brennkraftmaschinen, insbesondere für Einlaßventile dargestellt. Dabei wird ein in Fig. 1 gezeigter Stangenmaterialrohling 1 aus einem härtbaren Stahl wie beispielsweise aus X 45 CrSi 9 3 an einem Ende 2 erwärmt. Am erwärmten Ende 2 des Rohlings 1 wird dann eine Birne 3 (Fig. 2) durch Elektrostauchen angestaucht, wonach der Rohling 1 zu einem Ventil 4 ausgeschmiedet wird. Hierzu wird der Ventilschaft 5 und der Ventilteller 6 vorgeformt (Fig.3). Anschließend wird nach Fig. 4 das Ventil 4 eventuell zerspanend vorbearbeitet, wobei das Schaftende 7 und der Ventilteller 6 funktionell gestaltet wird und im Bereich des Endes 7 in den Ventilschaft 5 eine Keilnut 8 eingearbeitet wird.1 to 4 show individual stages of the valve shape in the manufacturing process of a valve for internal combustion engines, in particular for intake valves. A rod material blank 1 shown in FIG. 1 made of a hardenable steel such as X 45 CrSi 9 3 is heated at one end 2. At the heated end 2 of the blank 1, a pear 3 (FIG. 2) is then compressed by electric upsetting, after which the blank 1 is forged into a valve 4. For this purpose, the valve stem 5 and the valve plate 6 are preformed (FIG. 3). 4, the valve 4 is possibly machined, whereby the stem end 7 and the valve plate 6 are functionally designed and a keyway 8 is machined into the valve stem 5 in the region of the end 7.

Alternativ zu der beschriebenen Umformung des Einlaßventils 4 ist zu dessen Herstellung auch die Methode des Warmfließpressens denkbar. Dabei wird das Material in Stabform auf die Umformtemperatur aufgeheizt und durch eine Matrize mit Negativform des Ventils durchgepreßt.As an alternative to the shaping of the inlet valve 4 described, the method of hot extrusion is also conceivable for its production. The material in bar form is heated to the forming temperature and pressed through a die with a negative shape of the valve.

Die derartig ausgebildeten Ventile 4 werden zum Härten als Schüttgut 10 in einem Korb 11 aufgenommen und mit diesem in einen Härtofen 12 eingebracht. Im Härteofen 12 werden die Ventile 4 gleichmäßig und gleichzeitig bei einer Temperatur von etwa 950°C für die Dauer von 1-2 Stunden und Normalatmosphäre wärmebehandelt und danach gemeinsam aus der Ofenwärme in einem Ölbad 13 abgeschreckt, wodurch dieses auf etwa 100°C aufgewärmt wird (Fig. 5). In der Ofenwärme werden alle Oberflächenpartien und Bauteilquerschnitte der Ventile 4 gleichmäßig und somit die einzelnen funktionellen Ventilabschnitte wie der Ventilschaft 5, der Ventilteller 6, das Schaftende 7, die Keilnut 8 und der Ventiltellerboden 9 in gleicher Weise wärmebehandelt.The valves 4 designed in this way are received for hardening as bulk material 10 in a basket 11 and introduced into a hardening furnace 12 with the latter. The valves are in the hardening furnace 12 4 evenly and simultaneously heat-treated at a temperature of about 950 ° C for a period of 1-2 hours and normal atmosphere and then quenched together from the furnace heat in an oil bath 13, whereby this is heated to about 100 ° C (Fig. 5). In the furnace heat, all surface parts and component cross sections of the valves 4 are treated uniformly and thus the individual functional valve sections such as the valve stem 5, the valve plate 6, the shaft end 7, the keyway 8 and the valve plate bottom 9 are heat treated in the same way.

Die abgeschreckten Ventile 4 werden anschließend im Korb 11 in einen weiteren Ofen 14 geschoben und dort bei einer Temperatur von etwa 200±20°C ca. ½ - 1 Stunde lang dem Vorgang des Entspannungsglühens unterzogen. Dadurch werden Eigenspannungsspitzen im Gefüge, die beim Härten entstehen, abgebaut und gleichzeitig eine Gefügeumwandlung tetragonalen Plattenmartensites in kubischen Martensit erreicht. Dies verbessert die Zähigkeit des Ventilwerkstoffes und nivelliert unterschiedliche Härten zwischen den Ventilen 4. Diese werden hierbei auf eine Härte im Bereich von 57±3 HRC eingestellt. Fig. 6 zeigt dabei mit der Schnittschraffur 15 ein bearbeitetes, einheitlich und gleichmäßig durchgehärtetes Einzelventil 4.The quenched valves 4 are then pushed into a further furnace 14 in the basket 11 and there subjected to the relaxation annealing process at a temperature of approximately 200 ± 20 ° C. for about ½ - 1 hour. As a result, residual stress peaks in the structure that arise during hardening are reduced and, at the same time, a structural transformation of tetragonal plate marten sites into cubic martensite is achieved. This improves the toughness of the valve material and levels different hardnesses between the valves 4. These are adjusted to a hardness in the range of 57 ± 3 HRC. 6 shows the cut hatch 15, a machined, uniformly and uniformly hardened single valve 4.

Im gehärteten Zustand erfolgt die Endbearbeitung der Ventile 4 durch Schleifen oder Polieren zur Herstellung der geforderten Oberflächenqualität.In the hardened state, the valves 4 are finished by grinding or polishing to produce the required surface quality.

Claims (2)

Verfahren zum Härten von Einmetall-Ventilen, insbesondere von Einlaßventilen für Brennkraftmaschinen aus einem härtbaren Stahl, insbesondere aus X 45 CrSi 9 3,
dadurch gekennzeichnet,
daß unter Verzicht auf eine örtlich gezielte Sonderbehandlung einzelner Oberflächenpartien viele gleiche Ventile (4) gemeinsam und gleichzeitig einer für alle Oberflächenpartien und Bauteilquerschnitte gleichmäßig wirkenden Wärmebehandlung bei etwa 950°C in einem Härteofen (12) unterzogen und danach gemeinsam aus der Ofenwärme abgeschreckt werden und daß die Ventile (4) anschließend durch Entspannen bei einer Temperatur von etwa 200±20°C unter Beibehaltung ihrer durch die vorhergehende Wärmebehandlung geschaffenen martensitischen Gefügestruktur auf eine Härte im Bereich von 57±3 HRC eingestellt werden.Method for hardening single-metal valves, in particular inlet valves for internal combustion engines, made of hardenable steel, in particular of X 45 CrSi 9 3,
characterized by
that without a locally targeted special treatment of individual surface areas, many identical valves (4) are subjected to a heat treatment at about 950 ° C. in a hardening furnace (12), which acts uniformly for all surface areas and component cross sections, and are then quenched together from the furnace heat and that the valves (4) are then adjusted to a hardness in the range of 57 ± 3 HRC by relaxing at a temperature of about 200 ± 20 ° C while maintaining their martensitic structure created by the previous heat treatment. Verfahren nach Anspruch 1,
dadurch gekennzeichnet,
daß die Ventile (4) als Schüttgut (10) gehärtet werden.Method according to claim 1,
characterized by
that the valves (4) are hardened as bulk material (10).
EP95101756A 1994-03-03 1995-02-09 Method of hardening of metal valves, in particular intake valves for internal combustion engines Expired - Lifetime EP0670375B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4406896 1994-03-03
DE4406896A DE4406896C1 (en) 1994-03-03 1994-03-03 Martensitic age-hardening process for esp. alloyed steel inlet valves

Publications (2)

Publication Number Publication Date
EP0670375A1 true EP0670375A1 (en) 1995-09-06
EP0670375B1 EP0670375B1 (en) 1998-09-09

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EP95101756A Expired - Lifetime EP0670375B1 (en) 1994-03-03 1995-02-09 Method of hardening of metal valves, in particular intake valves for internal combustion engines

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EP (1) EP0670375B1 (en)
JP (1) JP2817029B2 (en)
DE (2) DE4406896C1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9181824B2 (en) * 2006-01-26 2015-11-10 Aubert & Duval Method for producing an internal combustion engine valve and valve obtained in this manner

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019180741A1 (en) * 2018-03-20 2019-09-26 Durovalves India Pvt. Ltd. Monometallic inlet valve for crail engine with hardened tappet end

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Publication number Priority date Publication date Assignee Title
DE1206455B (en) * 1959-08-14 1965-12-09 Daimler Benz Ag Method for hardening valves, in particular intake valves for internal combustion engines
DE1476045A1 (en) * 1964-01-10 1969-02-13 Eaton Yale & Towne Disc valve for internal combustion engines and process for its manufacture
JPS63169326A (en) * 1986-12-30 1988-07-13 Honda Motor Co Ltd Suction valve

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DE1216905B (en) * 1961-07-28 1966-05-18 Bbc Brown Boveri & Cie Device for uniform and rapid cooling of workpieces, preferably forged or cast parts
JPS5137250A (en) * 1974-09-26 1976-03-29 Dainippon Toryo Kk HANSHAGATAEKISHOHYOJISOCHI
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1206455B (en) * 1959-08-14 1965-12-09 Daimler Benz Ag Method for hardening valves, in particular intake valves for internal combustion engines
DE1476045A1 (en) * 1964-01-10 1969-02-13 Eaton Yale & Towne Disc valve for internal combustion engines and process for its manufacture
JPS63169326A (en) * 1986-12-30 1988-07-13 Honda Motor Co Ltd Suction valve

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BEDDOES G N: "VALVE MATERIALS AND DESIGN", POWDER METALLURGY, vol. 35, no. 4, 1 January 1992 (1992-01-01), pages 260 - 266, XP000327738 *
PATENT ABSTRACTS OF JAPAN vol. 12, no. 444 (C - 545) 22 November 1988 (1988-11-22) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9181824B2 (en) * 2006-01-26 2015-11-10 Aubert & Duval Method for producing an internal combustion engine valve and valve obtained in this manner

Also Published As

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EP0670375B1 (en) 1998-09-09
DE4406896C1 (en) 1995-06-29
JPH07268475A (en) 1995-10-17
JP2817029B2 (en) 1998-10-27
DE59503476D1 (en) 1998-10-15

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