EP0253176A2 - Method for heat treating steel work pieces - Google Patents

Method for heat treating steel work pieces Download PDF

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Publication number
EP0253176A2
EP0253176A2 EP87109238A EP87109238A EP0253176A2 EP 0253176 A2 EP0253176 A2 EP 0253176A2 EP 87109238 A EP87109238 A EP 87109238A EP 87109238 A EP87109238 A EP 87109238A EP 0253176 A2 EP0253176 A2 EP 0253176A2
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EP
European Patent Office
Prior art keywords
temperature
batch
charge
martensite
gas
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.)
Withdrawn
Application number
EP87109238A
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German (de)
French (fr)
Other versions
EP0253176A3 (en
Inventor
Willi Freppon
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.)
Evonik Operations GmbH
Original Assignee
Degussa GmbH
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Filing date
Publication date
Application filed by Degussa GmbH filed Critical Degussa GmbH
Publication of EP0253176A2 publication Critical patent/EP0253176A2/en
Publication of EP0253176A3 publication Critical patent/EP0253176A3/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C21D1/22—Martempering
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/16—Arrangements of air or gas supply devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/16—Arrangements of air or gas supply devices
    • F27B2005/161—Gas inflow or outflow

Definitions

  • the invention relates to a process for the heat treatment of batches of iron and steel parts, which are heated in a vacuum and cooled under pressure in an inert gas by inflowing and circulating gas, after a rapid cooling of the batch from annealing temperature to the martensite formation temperature by comparing the temperatures inside the batch and on the batch surface by throttling the gas circulation speed and / or the gas pressure, a temperature equalization of the total batch in the range of the martensite formation temperature is made possible before further cooling to the removal temperature from the furnace takes place.
  • the inert gas is usually circulated with a blower and directed onto the batch in the furnace by means of nozzles or baffles.
  • the batch of steel parts can be removed from the furnace when it has cooled to the point where there is no longer any oxidation in the air.
  • the steel heated to the hardening temperature is cooled in a quenching agent so rapidly to about room temperature that the formation of ferrite, pearlite and carbide is suppressed and the hardening structure "martensite" is formed.
  • the conversion to martensite begins during the rapid cooling at the so-called martensite formation temperature, which is dependent on the carbon content and the other alloy components of the steel. It is usually between 550 ° C and 150 ° C, for common tool steels around 200 ° C.
  • This object is achieved in that the temperature profile inside the batch is simulated using a computer program.
  • the temperature compensation takes place in such a way that when the martensite formation temperature dependent on the steel composition is reached on the batch surface, the gas circulation is reduced or completely throttled, after a temperature increase on the batch surface due to heat conduction from the interior of the batch to temperatures of 10 to 80 ° C above the martensite formation temperature Gas circulation increased again, and this alternating reduction in gas circulation is continued until a final temperature equalization between the inside of the batch and the surface of the batch has taken place in the martensite formation temperature interval.
  • the temperatures on the batch surface are advantageously measured by means of electrical temperature sensors, e.g. with thermocouples, and the gas circulation and / or the gas pressure are regulated from the measured data via a computer control.
  • a computer program is used in the computer control, into which the previously determined batch-specific parameters and the martensite formation temperature are entered. This computer program simulates the temperature profile inside the batch so that there is no need to install a temperature sensor there. As soon as the temperature sensor on the batch surface shows the previously entered martensite formation temperature, the gas circulation is automatically throttled. As a result, the temperature on the surface of the batch rises again, since there is an outflow of heat from the inside of the batch.
  • the gas circulation is increased again by the computer control until the temperature sensor on the batch surface again shows the martensite formation temperature.
  • the gas circulation is then throttled again until, after repeated throttling and increasing the gas circulation, the temperature between the surface of the batch and the interior of the batch has been equalized. It is then cooled to the removal temperature from the oven in the usual way.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Heat Treatment Processes (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Heat Treatment Of Articles (AREA)
  • Furnace Charging Or Discharging (AREA)

Abstract

For heat treating iron and steel work pieces, the latter are heated up in a vacuum and cooled by blasting with inert gas under pressure. Martensite is formed evenly over the entire charge if, after rapid cooling to martensite-forming temperature, temperature equalisation between charge surface and charge interior is brought about by slowing down the gas-circulating velocity. For this purpose, the temperature of the charge surface is measured and the temperature course in the charge interior simulated by means of a computer program into which the charge-specific parameters have been previously fed.

Description

Die Erfindung betrifft ein Verfahren zur Wärmebehandlung von Chargen aus Eisen- und Stahlteilen, die im Vakuum aufgeheizt und unter Druck in einem Inertgas durch Anströmen und Gasumwälzung abgekühlt werden, wobei nach einem schnellen Abkühlen der Charge von Glühtemperatur auf die Martensitbildungstemperatur durch Vergleich der Temperaturen im Chargeninnern und auf der Chargenoberfläche mittels Drosselung der Gasumwälzgeschwindigkeit und/oder des Gasdrucks ein Temperaturausgleich der Gesamtcharge im Bereich der Martensitbildungstemperatur ermöglicht wird, bevor eine weitere Abkühlung auf Entnahmetemperatur aus dem Ofen erfolgt.The invention relates to a process for the heat treatment of batches of iron and steel parts, which are heated in a vacuum and cooled under pressure in an inert gas by inflowing and circulating gas, after a rapid cooling of the batch from annealing temperature to the martensite formation temperature by comparing the temperatures inside the batch and on the batch surface by throttling the gas circulation speed and / or the gas pressure, a temperature equalization of the total batch in the range of the martensite formation temperature is made possible before further cooling to the removal temperature from the furnace takes place.

Es ist seit langem bekannt, Stahlteile in Vakuumöfen zu härten, indem sie unter Vakuum auf Temperaturen erhitzt werden, bei denen sich die Austenitphase als Gefüge bildet, und dann im Inertgas unter höherem Druck möglichst schnell abgekühlt werden. Dazu wird das Inertgas meist mit einem Gebläse umgewälzt und mittels Düsen oder Leitblechen auf die im Ofen befindliche Charge gerichtet. Die Stahlteile­charge kann dem Ofen entnommen werden, wenn sie soweit abgekühlt ist, daß keine Oxidation an der Luft mehr stattfindet.It has long been known to harden steel parts in vacuum furnaces by heating them under vacuum to temperatures at which the austenite phase forms as a structure, and then cooling them as quickly as possible in the inert gas under higher pressure. For this purpose, the inert gas is usually circulated with a blower and directed onto the batch in the furnace by means of nozzles or baffles. The batch of steel parts can be removed from the furnace when it has cooled to the point where there is no longer any oxidation in the air.

Da in einer zur Wärmebehandlung anstehenden Charge die Teile oft unterschiedliche Wandstärken besitzen, können dünne Teile bei der Entnahme aus dem Ofen beispielsweise auf 50°C abgekühlt sein, während die Temperatur dickerer Teile z.B. noch bei 250° C liegen kann. Das hat den Nachteil, daß sich in den verschiedenen Teilen einer Charge und auch in den einzelnen Teilen selbst unterschiedliche Gefüge ausbilden können.Since the parts in a batch to be heat-treated often have different wall thicknesses, thin parts can be cooled to 50 ° C. when removed from the furnace, for example, while the temperature of thicker parts may still be 250 ° C. This has the disadvantage that different structures can form in the different parts of a batch and also in the individual parts themselves.

Das gleiche gilt für Teile, die sich im Innern oder an der Oberfläche einer Charge befinden.The same applies to parts that are inside or on the surface of a batch.

Ein Verfahren und eine Vorrichtung zur Härtung von Stahlteilen ist beispielsweise in der DE-PS 28 39 807 beschrieben.A method and a device for hardening steel parts is described for example in DE-PS 28 39 807.

Bei der üblichen Abschreckhärtung wird der auf Härte­temperatur erwärmte Stahl in einem Abschreckmittel so rasch auf etwa Raumtemperatur abgekühlt, daß die Bildung von Ferrit, Perlit und Karbid unterdrückt wird und das Härtungsgefüge "Martensit" entsteht. Die Umwandlung in Martensit setzt während der raschen Abkühlung bei der sogenannten Martensit- Bildungstemperatur ein, die abhängig ist vom Kohlenstoffgehalt und den sonstigen Legierungsbestandteilen des Stahls. Sie liegt normalerweise zwischen 550° C und 150° C, für gebräuchliche Werkzeugstähle bei etwa 200° C.In conventional quench hardening, the steel heated to the hardening temperature is cooled in a quenching agent so rapidly to about room temperature that the formation of ferrite, pearlite and carbide is suppressed and the hardening structure "martensite" is formed. The conversion to martensite begins during the rapid cooling at the so-called martensite formation temperature, which is dependent on the carbon content and the other alloy components of the steel. It is usually between 550 ° C and 150 ° C, for common tool steels around 200 ° C.

Um einen Stahl zu härten, ist es nicht erforderlich, auch das Temperaturintervall der Martensit-Bildung rasch zu durchlaufen. Wird in diesem Bereich langsam abgekühlt, so wandelt sich der Austenit ziemlich gleichmäßig über den ganzen Querschnitt des Werkstücks Martensit um. Bei der anschließenden langsamen Abkühlung auf Raumtemperatur entsteht der volumengrößere Martensit an allen Stellen des Werkstücks fast gleichzeitig, im Gegensatz zur Abschreckhärtung, bei der der Martensit an den einzelnen Partien des Werkstücks zu verschiedenen Zeitpunkten entsteht und dadurch zu Spannungen, verbunden mit Formänderungen und Reißgefahr, führt. Solche Temperaturunterschiede treten allerdings auch bei einer langsamen Abkühlung im Martensitbereich zwischen Teilen im Innern und auf der Oberfläche einer Charge auf.In order to harden a steel, it is not necessary to go through the temperature interval of the formation of martensite quickly. If cooling is slow in this area, the austenite changes fairly uniformly over the entire cross-section of the martensite workpiece. During the subsequent slow cooling to room temperature, the larger-volume martensite is formed almost simultaneously on all parts of the workpiece, in contrast to quench hardening, in which the martensite is formed on the individual parts of the workpiece at different times and thus leads to tension, associated with changes in shape and risk of tearing . However, such temperature differences also occur during slow cooling in the martensite area between parts inside and on the surface of a batch.

Aus den "Fachberichte Hüttenpraxis Metallverarbeitung, Vol 23, Nr. 9, 1985, Seite 717-721" ist es bekannt, solche Temperaturunterschiede weitgehenst zu verhindern, indem mit Thermoelementen die Temperatur an verschiedenen Stellen der Charge gemessen und die Gasabkühlung durch Steuerung der Gasstromrichtung entsprechend variiert wird. In der Praxis treten allerdings Fälle auf, in denen die Temperatur innerhalb der Charge nicht mit einem Temperatursensor gemessen werden kann. Eine Regelung und Steuerung der Abkühlungsgeschwindigkeit durch Vergleich der Temperaturen auf der Chargenoberfläche und im Chargeninnern ist in diesem Fällen nicht möglich.From the "Technical reports metallurgical practice metal processing, Vol 23, No. 9, 1985, page 717-721", it is known to largely prevent such temperature differences by measuring the temperature at various points in the batch with thermocouples and the gas cooling by controlling the gas flow direction accordingly is varied. In practice, however, there are cases in which the temperature within the batch cannot be measured with a temperature sensor. In this case, it is not possible to regulate and control the cooling rate by comparing the temperatures on the surface of the batch and inside the batch.

Es war daher Aufgabe der vorliegenden Erfindung, ein Verfahren zur Wärmebehandlung von Chargen aus Eisen- und Stahlteilen,gemäß dem Oberbegriff des Patentanspruchs,zu entwickeln, bei dem eine gleichmäßige Martensitbildung innerhalb der einzelnen Teile und innerhalb der gesamten Charge auch ohne Messung der Temperatur im Chargeninnern erreicht werden kann.It was therefore an object of the present invention to develop a method for the heat treatment of batches made of iron and steel parts, according to the preamble of the claim, in which a uniform formation of martensite within the individual parts and within the entire batch even without measuring the temperature inside the batch can be reached.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß der Temperaturverlauf im Chargeninnern mittels eines Rechenprogramms simuliert wird.This object is achieved in that the temperature profile inside the batch is simulated using a computer program.

Der Temperaturausgleich erfolgt in der Weise, daß beim Erreichen der von der Stahlzusammensetzung abhängigen Martensitbildungstemperatur auf der Chargenoberfläche die Gasumwälzung vermindert oder völlig gedrosselt wird, nach einer Temperaturerhöhung auf der Chargenoberfläche infolge Wärmeleitung aus dem Chargeninnern auf Temperaturen von 10 bis 80° C oberhalb der Martensitbildungstemperatur die Gasumwälzung wieder gesteigert, und dieses abwechselnde Vermindern der Gasumwälzung solange fortgeführt wird, bis ein endgültiger Temperaturausgleich zwischen Chargeninnerem und Chargenoberfläche im Martensitbildungstemperaturintervall erfolgt ist.The temperature compensation takes place in such a way that when the martensite formation temperature dependent on the steel composition is reached on the batch surface, the gas circulation is reduced or completely throttled, after a temperature increase on the batch surface due to heat conduction from the interior of the batch to temperatures of 10 to 80 ° C above the martensite formation temperature Gas circulation increased again, and this alternating reduction in gas circulation is continued until a final temperature equalization between the inside of the batch and the surface of the batch has taken place in the martensite formation temperature interval.

Die Temperaturen auf der Chargenoberfläche werden vorteilhafterweise mittels elektrischer Temperatursensoren gemessen, z.B. mit Thermoelementen, und aus den gemessenen Daten über eine Computersteuerung die Gasumwälzung und/oder der Gasdruck geregelt. In der Computersteuerung wird dabei ein Rechenprogramm eingesetzt, in das die zuvor ermittelten chargenspezifischen Parameter und die Martensitbildungstemperatur eingegeben werden. Mit diesem Rechenprogramm wird der Temperaturverlauf im Chargeninnern simuliert, so daß man dort keinen Temperatursensor anzubringen braucht. Sobald der Temperatursensor auf der Chargenoberfläche die zuvor eingegebene Martensitbildungstemperatur anzeigt, wird die Gasumwälzung automatisch gedrosselt. Dadurch steigt die Temperatur auf der Chargenoberfläche wieder an, da aus dem Chargeninneren ein Wärmeabfluß nach außen erfolgt. Nach Erreichen einer Temperatur, die beispielsweise 20° C über eingegebenen Martensitbildungstemperatur liegen kann, wird die Gasumwälzung durch die Computer-Steuerung wieder erhöht, bis der Temperatursensor auf der Chargenoberfläche erneut die Martensitbildungstemperatur anzeigt. Anschließend wird die Gasumwälzung wieder gedrosselt, bis nach mehrmaligem Drosseln und Erhöhen der Gasumwälzung ein Temperaturausgleich zwischen Chargenoberfläche und Chargeninnerem erfolgt ist. Anschließend erfolgt das Abkühlen auf die Entnahmetemperatur aus dem Ofen auf üblicher Weise.The temperatures on the batch surface are advantageously measured by means of electrical temperature sensors, e.g. with thermocouples, and the gas circulation and / or the gas pressure are regulated from the measured data via a computer control. A computer program is used in the computer control, into which the previously determined batch-specific parameters and the martensite formation temperature are entered. This computer program simulates the temperature profile inside the batch so that there is no need to install a temperature sensor there. As soon as the temperature sensor on the batch surface shows the previously entered martensite formation temperature, the gas circulation is automatically throttled. As a result, the temperature on the surface of the batch rises again, since there is an outflow of heat from the inside of the batch. After reaching a temperature which can be 20 ° C above the entered martensite formation temperature, the gas circulation is increased again by the computer control until the temperature sensor on the batch surface again shows the martensite formation temperature. The gas circulation is then throttled again until, after repeated throttling and increasing the gas circulation, the temperature between the surface of the batch and the interior of the batch has been equalized. It is then cooled to the removal temperature from the oven in the usual way.

Claims (1)

Verfahren zur Wärmebehandlung von Chargen aus Eisen- und Stahlteilen, die im Vakuum aufgeheizt und unter Druck in einem Inertgas durch Anströmen und Gasumwälzung abgekühlt werden, wobei nach einem schnellen Abkühlen der Charge von Glühtemperatur auf die Martensitbildungstemperatur durch Vergleich der Temperaturen im Chargeninnern und auf der Chargenoberfläche mittels Drosselung der Gasumwälzge­schwindigkeit und/oder des Gasdrucks ein Temperaturaus­gleich der Gesamtcharge im Bereich der Martensitbildungs­temperatur ermöglicht wird, bevor eine weitere Abkühlung auf die Entnahmetemperatur aus dem Ofen erfolgt,
dadurch gekennzeichnet,
daß der Temperaturverlauf im Chargeninnern mittels eines Rechenprogramms simuliert wird.Process for the heat treatment of batches of iron and steel parts, which are heated in a vacuum and cooled under pressure in an inert gas by inflow and gas circulation, whereby after a rapid cooling of the batch from annealing temperature to the martensite formation temperature by comparison of the temperatures inside the batch and on the batch surface by throttling the gas circulation rate and / or the gas pressure, a temperature equalization of the total batch in the area of the martensite formation temperature is made possible before further cooling to the removal temperature from the furnace takes place,
characterized,
that the temperature profile inside the batch is simulated using a computer program.
EP87109238A 1986-07-09 1987-06-26 Method for heat treating steel work pieces Withdrawn EP0253176A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863623105 DE3623105C1 (en) 1986-07-09 1986-07-09 Process for the heat treatment of steel parts
DE3623105 1986-07-09

Publications (2)

Publication Number Publication Date
EP0253176A2 true EP0253176A2 (en) 1988-01-20
EP0253176A3 EP0253176A3 (en) 1989-08-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP87109238A Withdrawn EP0253176A3 (en) 1986-07-09 1987-06-26 Method for heat treating steel work pieces

Country Status (3)

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EP (1) EP0253176A3 (en)
JP (1) JPS6326308A (en)
DE (1) DE3623105C1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0538575A1 (en) * 1991-10-25 1993-04-28 Ipsen Industries International Gesellschaft Mit Beschränkter Haftung Method for cooling a charge of workpieces during a heat treatment process
EP0621344A1 (en) * 1993-04-21 1994-10-26 Ipsen Industries International Gesellschaft Mit Beschränkter Haftung Flexible adaptive quenching
WO2006042538A1 (en) * 2004-10-22 2006-04-27 Ald Vacuum Technologies Gmbh Method for the low-warping case hardening of metallic parts

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4452607B2 (en) 2004-03-05 2010-04-21 順一 島田 Illumination device, filter device, image display device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58224121A (en) * 1982-06-22 1983-12-26 Sumitomo Metal Ind Ltd Controlling method of heating in tight annealing furnace
JPS59110735A (en) * 1982-12-13 1984-06-26 Kawasaki Steel Corp Method for cooling coil
EP0129701A1 (en) * 1983-06-22 1985-01-02 Schmetz GmbH & Co. KG Unternehmensverwaltung Oven device for cooling a workload, especially of metallic workpieces

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58224121A (en) * 1982-06-22 1983-12-26 Sumitomo Metal Ind Ltd Controlling method of heating in tight annealing furnace
JPS59110735A (en) * 1982-12-13 1984-06-26 Kawasaki Steel Corp Method for cooling coil
EP0129701A1 (en) * 1983-06-22 1985-01-02 Schmetz GmbH & Co. KG Unternehmensverwaltung Oven device for cooling a workload, especially of metallic workpieces

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
FACHBERICHTE H]TTENPRAXIS METALLWEITERVERARBEITUNG, Band 23, Nr. 9, 1985, Seiten 717-721, Sprechsaal-Verlag, Coburg, DE; P. LISTEMANN: "Neuere Entwicklungen auf dem Gebiet der Vakuum-W{rmebehandlung" *
PATENT ABSTRACTS OF JAPAN, Band 8, Nr. 225 (C-247)[1662], 16. Oktober 1984; & JP-A-59 110 735 (KAWASAKI SEITETSU K.K.) 26-06-1984 *
PATENT ABSTRACTS OF JAPAN, Band 8, Nr. 71 (C-217)[1508], 3. April 1984; & JP-A-58 224 121 (SUMITOMO KINZOKU KOGYO K.K.) 26-12-1983 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0538575A1 (en) * 1991-10-25 1993-04-28 Ipsen Industries International Gesellschaft Mit Beschränkter Haftung Method for cooling a charge of workpieces during a heat treatment process
EP0621344A1 (en) * 1993-04-21 1994-10-26 Ipsen Industries International Gesellschaft Mit Beschränkter Haftung Flexible adaptive quenching
WO2006042538A1 (en) * 2004-10-22 2006-04-27 Ald Vacuum Technologies Gmbh Method for the low-warping case hardening of metallic parts

Also Published As

Publication number Publication date
JPS6326308A (en) 1988-02-03
DE3623105C1 (en) 1987-12-03
EP0253176A3 (en) 1989-08-16

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Effective date: 19910724

RIN1 Information on inventor provided before grant (corrected)

Inventor name: FREPPON, WILLI