EP1248862B1 - Method for austempering steel parts - Google Patents
Method for austempering steel parts Download PDFInfo
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- EP1248862B1 EP1248862B1 EP00984836A EP00984836A EP1248862B1 EP 1248862 B1 EP1248862 B1 EP 1248862B1 EP 00984836 A EP00984836 A EP 00984836A EP 00984836 A EP00984836 A EP 00984836A EP 1248862 B1 EP1248862 B1 EP 1248862B1
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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
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
Definitions
- the invention relates to a method for bainitizing Steel parts according to the preamble of the main claim.
- bainitizing is meant a heat treatment of Steel, which is first an “austenitizing” of steel, a subsequent quenching to a temperature above the so-called “martensite” start temperature and holding the Steel at this temperature for a given time includes.
- the austenitizing of steel, a subsequent Deterrence and the isothermal conversion of austenite in bainite above the martensite start temperature is further for example, also from US 5,628,045; EP-A-0 707 088 and EP-A-0 896 068.
- the inventive method for bainitizing steel parts as claimed in claim 1 over the prior art has the advantage that thus an at least almost complete conversion of Austenite in bainite, i. a purely bainitic structure, achievable, while the hardness of the afterwards obtained steel parts in a simple manner by the Process parameters is controllable.
- the obtained steel parts improved strength properties, for example with regard to a pulsating pressure-threshold load, on.
- a further advantage is that the inventive Process in a simple manner in mass production can be used without significant interference with existing Production processes or investments in production facilities would be required.
- the inventive method is further advantageous quenching of series batches of steel parts at low salt bath temperatures while producing as pure as possible bainite, ie without proportion of continuous bainite, possible, in addition, a uniform quenching intensity is achieved within a batch.
- the start temperature T 2 which is preferably slightly above the martensite start temperature T M , that in the ZTU image during quenching the pearlite microstructure is passed through.
- the core hardness of the implementation by the process according to the invention obtained steel parts the duration of the first period, i. of holding in the first salt bath or oil bath, and also the temperature of the first salt bath can be adjusted. It applies in general, that the core hardness of the obtained bainitic The shorter the structure of the steel parts Residence time in the first salt bath is selected.
- the resulting heat of reaction can be used to advantage, the steel parts after completion of the first period of a start temperature T 2 to a finish temperature T 3 on which the steel parts are then held for the duration of the second period. This results in an energy saving and a quick and uniform heating of the steel parts.
- the figure shows a schematic diagram of a so-called “ZTU image” (Time-Temperature Conversion Chart) the Conversion of austenite into bainite by means of a graded Bainite.
- ZTU image Time-Temperature Conversion Chart
- the invention is exemplified by the bainitization of steel Type 100Cr6, material no. 1.3505, explained.
- steel parts of this type are first austenitized in a conventional manner and then starting from a quenching temperature T 1 of 830 ° C to 870 ° C, for example 850 ° C, in a conventional manner in a first salt bath to a starting temperature T 2 quenched, which is above the martensite start temperature T M of the steel parts.
- the martensite start temperature T M is in the illustrated example at about 205 ° C to 215 ° C.
- the perlite structure area is also further 11 registered, in the inventive Bainitization by graded thermal conversion is not is going through.
- This second, isothermal storage at the finish temperature T 3 lasts for a second period ⁇ t iso, 2 , which is completed as soon as the bainite microstructure 12 is reached at the time t 3 , ie as soon as at least almost complete conversion of austenite into pure bainite is done.
- the period .DELTA.t iso, 2 or the time and t 3 may be different, selected from the illustration in the figure, for example for reasons of process stability such or extended, that the coordinate (T 3, T 3 ) lies within the bainite structure region 12.
- the achievement of the limitation of the bainite structure region 12 in the figure during the second period .DELTA.t iso, 2 is thus only to be understood as a minimum requirement for the length of the second time period .DELTA.t iso, 2 .
- the second, isothermal storage of the steel parts at the finish temperature T 3 takes place in a second salt bath or oil bath or alternatively also in a holding furnace according to the recirculation principle.
- the steel parts are then stored isothermally in the first salt bath over the first period .DELTA.t iso, 1 , which lasts for 5 minutes to 30 minutes, preferably 20 minutes.
- the steel parts are converted into a holding furnace according to the circulating air principle, which has a finish temperature T 3 of 240 ° C. to 280 ° C., in particular 260 ° C.
- the steel parts are then stored at this finish temperature T 3 over the second period ⁇ t iso, 2 , which lasts between 200 min and 400 min, preferably 250 min to 270 min.
- a second salt bath with the finishing temperature T 3 can also be used.
- a preferred embodiment of the method according to the invention further provides that the heat of reaction formed in the formation of the bainite microstructure is at least partially used for heating the steel parts from the start temperature T 2 to the finish temperature T 3 or for heating the holding furnace.
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Abstract
Description
Die Erfindung betrifft ein Verfahren zum Bainitisieren von Stahlteilen nach der Gattung des Hauptanspruches.The invention relates to a method for bainitizing Steel parts according to the preamble of the main claim.
Unter "Bainitisieren" versteht man eine Wärmebehandlung von Stahl, die zunächst ein "Austenitisieren" des Stahles, eine nachfolgende Abschreckung auf eine Temperatur oberhalb der sogenannten "Martensit"-Starttemperatur und ein Halten des Stahles auf dieser Temperatur über eine vorgegebene Zeit umfaßt.By "bainitizing" is meant a heat treatment of Steel, which is first an "austenitizing" of steel, a subsequent quenching to a temperature above the so-called "martensite" start temperature and holding the Steel at this temperature for a given time includes.
Mit dieser Vorgehensweise, die auch als "isothermische Umwandlung" von Austenit in Bainit bezeichnet wird, ist es möglich, einen Stahl zu erhalten, der, je nach Zielsetzung und über die Temperatur und Haltedauer steuerbar, vollständig oder teilweise von einem austenitischen Gefüge in ein bainitisches Gefüge umgewandelt worden ist.With this approach, also called "isothermal Conversion "of austenite in bainite is called, it is possible to obtain a steel, depending on the objective and controllable over the temperature and holding time, wholly or partly of an austenitic structure has been converted into a bainitic structure.
Hinsichtlich weiterer Details zum Austenitisieren und die erläuterte Bainitisierung von Stahl, die an sich seit langem bekannt sind, sei beispielsweise auf E. Zimmermann, "Werkstoffkunde und Werkstoffprüfung", Hermann Schrödel Verlag, 1962, Seiten 38, 39 und 74 bis 79, verwiesen.For further details on austenitizing and the explained bainitization of steel, which in itself for a long time are known, for example, to E. Zimmermann, "Materials Science and Materials Testing", Hermann Schrödel Verlag, 1962, pages 38, 39 and 74 to 79, referenced.
Das Austenitisieren von Stahl, eine anschließende Abschreckung und die isothermische Umwandlung von Austenit in Bainit oberhalb der Martensit-Starttemperatur ist weiter beispielsweise auch aus US 5,628, 045; EP-A-0 707 088 und EP-A-0 896 068 bekannt.The austenitizing of steel, a subsequent Deterrence and the isothermal conversion of austenite in bainite above the martensite start temperature is further for example, also from US 5,628,045; EP-A-0 707 088 and EP-A-0 896 068.
Die Bainitisierung von zuvor austenitisierten Stählen erfolgt bisher weiter vielfach in Bädern, sogenannten Salzwarmbädern. Dazu wird der Stahl nach der Abschreckung vom Beginn der Bainit-Umwandlung (sogenannter Bainit-Start) bis zum Ende der Bainit-Umwandlung (sogenannter Bainit-Finish) bei einer konstanten Temperatur und einer entsprechenden, geeignet gewählten Haltezeit in diesem Salzwarmbad ohne Unterbrechung gelagert.Bainitization of previously austenitized steels So far, there are many more in so-called baths Salt hot baths. For this, the steel is after the deterrent from the beginning of the bainite transformation (so-called bainite start) until the end of the bainite transformation (so-called bainite finish) at a constant temperature and a corresponding, suitably selected holding time in this Salt bath stored without interruption.
Schließlich wurde auch bereits vorgeschlagen, den zu bainitisierenden Stahl nach Ablauf einer definierten Verweilzeit in dem Salzwarmbad in einen mit Umluft betriebenen Halteofen umzusetzen, um somit eine vollständige Umwandlung von Austenit in Bainit zu erreichen. Der Halteofen weist dazu die gleiche Temperatur auf wie das Salzwarmbad.Finally, it has already been suggested that bainitizing steel after a defined Residence time in the salt bath in one with circulating air implemented holding furnace, thus a complete Converting austenite into bainite. Of the Holding furnace has the same temperature as the Salt bath.
Das erfindungsgemäße Verfahren zum Bainitisieren von Stahlteilen wie in Anspruch 1 beansprucht hat gegenüber dem Stand der Technik den Vorteil, daß damit eine zumindest nahezu vollständige Umwandlung von Austenit in Bainit, d.h. ein rein bainitisches Gefüge, erreichbar ist, wobei gleichzeitig die Härte der danach erhaltenen Stahlteile in einfacher Weise durch die Verfahrensparameter steuerbar ist. Insbesondere weisen die erhaltenen Stahlteile verbesserte Festigkeitseigenschaften, beispielsweise hinsichtlich einer pulsierenden Druck-Schwell-Belastung, auf.The inventive method for bainitizing steel parts as claimed in claim 1 over the prior art has the advantage that thus an at least almost complete conversion of Austenite in bainite, i. a purely bainitic structure, achievable, while the hardness of the afterwards obtained steel parts in a simple manner by the Process parameters is controllable. In particular, the obtained steel parts improved strength properties, for example with regard to a pulsating pressure-threshold load, on.
Weiter ist vorteilhaft, daß durch das erfindungsgemäße Verfahren die bisher erforderliche Zeit zur Umwandlung von Austenit in Bainit deutlich verkürzt werden kann. Somit ergeben sich auch erhebliche Kostenvorteile bei der Durchführung des erfindungsgemäßen Verfahrens.It is also advantageous that by the method according to the invention the time required to convert Austenite in bainite can be significantly shortened. Consequently There are also significant cost advantages in the Implementation of the method according to the invention.
Vorteilhaft ist weiter, daß sich das erfindungsgemäße Verfahren in einfacher Weise in der Serienfertigung einsetzen läßt, ohne daß wesentliche Eingriffe in bestehende Fertigungsabläufe oder Investitionen in Fertigungsanlagen erforderlich wären.A further advantage is that the inventive Process in a simple manner in mass production can be used without significant interference with existing Production processes or investments in production facilities would be required.
Durch das erfindungsgemäße Verfahren ist weiter vorteilhaft die Abschreckung von Serienchargen von Stahlteilen bei niedrigen Salzbadtemperaturen unter gleichzeitiger Erzeugung von möglichst reinem Bainit, d.h. ohne Anteil von kontinuierlichem Bainit, möglich, wobei zudem eine gleichmäßige Abschreckintensität innerhalb einer Charge erzielt wird. Insbesondere wird durch die Wahl der Start-Temperatur T2, die bevorzugt wenig oberhalb der Martensit-Starttemperatur TM liegt, vorteilhaft vermieden, daß in dem ZTU-Bild beim Abschrecken der Perlit-Gefügebereich durchlaufen wird.The inventive method is further advantageous quenching of series batches of steel parts at low salt bath temperatures while producing as pure as possible bainite, ie without proportion of continuous bainite, possible, in addition, a uniform quenching intensity is achieved within a batch. In particular, it is advantageously avoided by the selection of the start temperature T 2 , which is preferably slightly above the martensite start temperature T M , that in the ZTU image during quenching the pearlite microstructure is passed through.
Vorteilhafte Weiterbildungen der Erfindung ergeben sich aus den in den Unteransprüchen genannten Maßnahmen. Advantageous developments of the invention will become apparent the measures mentioned in the dependent claims.
So ist vorteilhaft, daß die Kernhärte der nach Durchführung des erfindungsgemäßen Verfahrens erhaltenen Stahlteile durch die Dauer des ersten Zeitraumes, d.h. des Haltens in dem ersten Salzwarmbad oder Ölbad, und auch die Temperatur des ersten Salzwarmbades eingestellt werden kann. Dabei gilt generell, daß die Kernhärte des erhaltenen bainitischen Gefüges der Stahlteile desto geringer ist, je kürzer die Verweildauer im ersten Salzwarmbad gewählt wird.So it is advantageous that the core hardness of the implementation by the process according to the invention obtained steel parts the duration of the first period, i. of holding in the first salt bath or oil bath, and also the temperature of the first salt bath can be adjusted. It applies in general, that the core hardness of the obtained bainitic The shorter the structure of the steel parts Residence time in the first salt bath is selected.
Gleiches gilt vorteilhaft auch für das Umsetzen der Stahlteile in einen Halteofen nach dem Umluftprinzip bzw. in ein zweites Salzbad mit erhöhter Temperatur des zweiten Zeitraumes. Auch in diesem Fall ist die Kernhärte des erhaltenen, bevorzugt rein bainitischen Gefüges der Stahlteile eine Funktion der Finish-Temperatur und der Dauer dieses zweiten Zeitraumes.The same applies advantageous for the implementation of the Steel parts in a holding furnace according to the circulating air principle or in a second salt bath with elevated temperature of the second Period. Also in this case the core hardness of the obtained, preferably pure bainitic structure of Steel parts a function of the finish temperature and the duration this second period.
Da es sich bei der Umwandlung eines Austenit-Gefüges in ein Bainit-Gefüge um eine exotherme Reaktion handelt, kann weiter vorteilhaft die entstehende Reaktionswärme dazu genutzt werden, die Stahlteile nach Abschluß des ersten Zeitraumes von einer Start-Temperatur T2 auf eine Finish-Temperatur T3 zu erwärmen, auf der die Stahlteile dann über die Dauer des zweiten Zeitraumes gehalten werden. Damit ergibt sich eine Energieersparnis und ein schnelles und gleichmäßiges Erwärmen der Stahlteile.Since it is an exothermic reaction in the transformation of an austenite microstructure into a bainite microstructure, the resulting heat of reaction can be used to advantage, the steel parts after completion of the first period of a start temperature T 2 to a finish temperature T 3 on which the steel parts are then held for the duration of the second period. This results in an energy saving and a quick and uniform heating of the steel parts.
Ausführungsbeispiele der Erfindung werden anhand der Zeichnung und in der nachfolgenden Beschreibung näher erläutert.Embodiments of the invention will be described with reference to FIGS Drawing and explained in more detail in the following description.
Die Figur zeigt eine Prinzipskizze eines sogenannten "ZTU-Bildes" (Zeit-Temperatur-Umwandlungsschaubild) der Umwandlung von Austenit in Bainit mittels einer gestuften Bainitumwandlung.The figure shows a schematic diagram of a so-called "ZTU image" (Time-Temperature Conversion Chart) the Conversion of austenite into bainite by means of a graded Bainite.
Die Erfindung wird am Beispiel der Bainitisierung von Stahl des Typs 100Cr6, Werkstoff-Nr. 1.3505, erläutert.The invention is exemplified by the bainitization of steel Type 100Cr6, material no. 1.3505, explained.
Dazu werden zunächst Stahlteile dieses Typs in an sich bekannter Weise austenitisiert und danach ausgehend von einer Abschreck-Temperatur T1 von 830°C bis 870°C, beispielsweise 850°C, in an sich bekannter Weise in einem ersten Salzwarmbad auf eine Start-Temperatur T2 abgeschreckt, die oberhalb der Martensit-Starttemperatur TM der Stahlteile liegt. Die Martensit-Starttemperatur TM liegt im erläuterten Beispiel bei ca. 205°C bis 215°C.For this purpose, steel parts of this type are first austenitized in a conventional manner and then starting from a quenching temperature T 1 of 830 ° C to 870 ° C, for example 850 ° C, in a conventional manner in a first salt bath to a starting temperature T 2 quenched, which is above the martensite start temperature T M of the steel parts. The martensite start temperature T M is in the illustrated example at about 205 ° C to 215 ° C.
Dies wird anhand der Figur erläutert, die in einem ZTU-Bild
5 zeigt, daß der Stahl zunächst als Austenit in einem
Austenit-Gefügebereich 15 vorliegt, und zu einem Zeitpunkt
t0 von der Abschreck-Temperatur T1 innerhalb eines Zeitraumes
von typischerweise 5 s bis 15 s auf die Start-Temperatur
T2 abgeschreckt wird. Zu dem Zeitpunkt t1 beginnt
dann ein erster Zeitraum, der über eine Zeitdauer Δtiso, 1 andauert,
und währenddessen der Stahl bzw. die Stahlteile in
einem ersten Salzwarmbad in an sich bekannter Weise bei der
zumindest näherungsweise konstanten Start-Temperatur T2
gehalten werden. Anstelle des Salzwarmbades kann im übrigen
auch ein Ölbad treten.This will be explained with reference to the figure which shows in a
In dem ZTU-Bild 5 ist weiter eingetragen, daß während des
ersten Zeitraumes Δtiso, 1 der zuvor in dem Austenit-Gefügebereich
15 vorliegende Austenit sich beginnt, in Bainit
umzuwandeln. Dieser Beginn der Bainitumwandlung erfolgt,
sobald die in dem ZTU-Bild eingetragene Umwandlungskurve 16,
die den zeitlichen Verlauf der bei dem erfindungsgemäßen
Verfahren eingesetzten Temperatur darstellt, in den Bainitumwandlungsbereich
13 eintritt.It is further noted in the ZTU
Die Umwandlung von Austenit in Bainit ist abgeschlossen,
sobald die Umwandlungskurve 16 in dem ZTU-Bild 5 den Bainit-Gefügebereich
12 erreicht, in dem die Stahlteile als reines
Bainit-Gefüge vorliegen.The conversion of austenite to bainite is complete,
Once the
In dem ZTU-Bild 5 ist im übrigen weiter auch der Perlit-Gefügebereich
11 eingetragen, der bei der erfindungsgemäßen
Bainitisierung durch gestufte thermische Umwandlung nicht
durchlaufen wird.Incidentally, in the ZTU
Nachdem das isotherme Lagern der Stahlteile bei der Start-Temperatur T2 über den ersten Zeitraum Δtiso, 1 zum Zeitpunkt t2 in dem ersten Salzwarmbad abgeschlossen ist, werden die Stahlteile anschließend bei einer Finish-Temperatur T3, die oberhalb der Start-Temperatur T2 liegt, zumindest näherungsweise isotherm gelagert.After the isothermal storage of the steel parts at the start temperature T 2 over the first period .DELTA.t iso, 1 is completed at time t 2 in the first salt bath, the steel parts are then at a finish temperature T 3 , which is above the start temperature T 2 is at least approximately isothermally stored.
Dieses zweite, isotherme Lagern bei der Finish-Temperatur T3
dauert über einen zweiten Zeitraum Δtiso, 2 an, der
abgeschlossen ist, sobald zum Zeitpunkt t3 der Bainit-Gefügebereich
12 erreicht ist, d.h. sobald eine zumindest
nahezu vollständige Umwandlung von Austenit in reines Bainit
erfolgt ist. Dabei sei betont, daß der Zeitraum Δtiso, 2 bzw.
der Zeitpunkt t3 auch, abweichend von der Darstellung in der
Figur und beispielsweise aus Gründen der Prozeßstabilität,
derart gewählt bzw. ausgedehnt sein kann, daß die Koordinate
(t3, T3) innerhalb des Bainit-Gefügebereiches 12 liegt. Das
Erreichen der Begrenzung des Bainit-Gefügebereiches 12 in
der Figur während des zweiten Zeitraumes Δtiso, 2 ist somit
lediglich als Minimalerfordernis für die Länge des zweiten
Zeitraumes Δtiso, 2 zu verstehen.This second, isothermal storage at the finish temperature T 3 lasts for a second period Δt iso, 2 , which is completed as soon as the
Das zweite, isotherme Lagern der Stahlteile bei der Finish-Temperatur T3 erfolgt in einem zweiten Salzwarmbad oder Ölbad oder alternativ auch in einem Halteofen nach dem Umluftprinzip.The second, isothermal storage of the steel parts at the finish temperature T 3 takes place in a second salt bath or oil bath or alternatively also in a holding furnace according to the recirculation principle.
Nach Abschuß der erläuterten gestuften Bainitumwandlung folgt dann in bekannter Weise die Ausfahrt, Kühlung und Reinigung der erhaltenen Stahlteile.After firing the illustrated stepped bainite transformation then follows in a known manner the exit, cooling and Cleaning of the obtained steel parts.
Im einzelnen wird in dem erläuterten Ausführungsbeispiel, nach dem Austenitisieren der Stahlteile, zunächst ein Abschrecken der zu behandelnden Charge in dem ersten Salzwarmbad bei einer Start-Temperatur T2 von 215°C bis 230°C vorgenommen. Besonders bevorzugt ist eine Temperatur von 220°C.Specifically, in the illustrated embodiment, after Austenitisieren the steel parts, first a quenching of the charge to be treated in the first salt bath at a starting temperature T 2 of 215 ° C to 230 ° C made. Particularly preferred is a temperature of 220 ° C.
Bei dieser Start-Temperatur T2 werden die Stahlteile dann isotherm in dem ersten Salzwarmbad über den ersten Zeitraum Δtiso, 1 gelagert, der über 5 min bis 30 min, bevorzugt 20 min, andauert.At this starting temperature T 2 , the steel parts are then stored isothermally in the first salt bath over the first period .DELTA.t iso, 1 , which lasts for 5 minutes to 30 minutes, preferably 20 minutes.
Danach erfolgt dann zum Zeitpunkt t2 ein Umsetzen der Stahlteile in einen Halte-ofen nach dem Umluftprinzip, der eine Finish-Temperatur T3 von 240°C bis 280°C, insbesondere 260°C, aufweist. Die Stahlteile werden dann bei dieser Finish-Temperatur T3 über den zweiten Zeitraum Δtiso, 2, der zwischen 200 min und 400 min, bevorzugt 250 min bis 270 min, andauert, gelagert.Thereafter, at the time t 2, the steel parts are converted into a holding furnace according to the circulating air principle, which has a finish temperature T 3 of 240 ° C. to 280 ° C., in particular 260 ° C. The steel parts are then stored at this finish temperature T 3 over the second period Δt iso, 2 , which lasts between 200 min and 400 min, preferably 250 min to 270 min.
Alternativ kann anstelle eines Halteofens jedoch auch ein zweites Salzwarmbad mit der Finish-Temperatur T3 eingesetzt werden.Alternatively, instead of a holding furnace, however, a second salt bath with the finishing temperature T 3 can also be used.
Eine bevorzugte Ausgestaltung des erfindungsgemäßen Verfahrens sieht weiter vor, daß die bei der Bildung des Bainit-Gefüges entstehende Reaktionswärme zumindest teilweise zum Erwärmen der Stahlteile von der Start-Temperatur T2 auf die Finish-Temperatur T3 bzw. zur Beheizung des Halteofens genutzt wird.A preferred embodiment of the method according to the invention further provides that the heat of reaction formed in the formation of the bainite microstructure is at least partially used for heating the steel parts from the start temperature T 2 to the finish temperature T 3 or for heating the holding furnace.
Insgesamt wird durch das erläuterte Verfahren eine deutliche Verkürzung der Gesamt-Bainitumwandlungszeit erreicht, die im erläuterten Ausführungsbeispiel nunmehr ca. 300 min beträgt.Overall, the illustrated method is a clear Shortening of the total bainite conversion time reached in the explained embodiment is now about 300 min.
Damit ergibt sich gegenüber bekannten Verfahren, d.h. dem isothermen Lagern der Stahlteile bei der Start-Temperatur T2 bis zum Erreichen des reinen Bainit-Gefüges eine Zeitersparnis von typischerweise ca. 60 min. This results in comparison to known methods, ie the isothermal storage of the steel parts at the starting temperature T 2 until reaching the pure bainite microstructure, a time savings of typically about 60 min.
Die durch das erläuterte Verfahren hergestellten bzw. behandelten Stahlteile mit bainitischem Gefüge weisen abschließend eine gegenüber dem Ausgangsmaterial reduzierte Kernhärte von 650 HV10 bis 700 HV10 auf.The produced by the described method or treated steel parts with bainitic structure point finally a reduced compared to the starting material Core hardness from 650 HV10 to 700 HV10.
Gleichzeitig ergab sich eine deutliche Festigkeitssteigerung der Stahlteile bei pulsierender Druck-Schwell-Belastung.At the same time there was a significant increase in strength the steel parts with pulsating pressure-threshold load.
Claims (9)
- Process for austempering steel parts, comprising the process steps of: a.) austenitizing the steel parts, b.) quenching the steel parts to a starting temperature (T2) which is above the martensite starting temperature (TM) of the steel parts, c.) at least approximately isothermally holding the steel parts at the starting temperature (T2) for a first period of time (Δtiso,1), which lasts for 5 minutes to 30 min, and d.) at least approximately isothermally holding the steel parts in a holding furnace using the circulated air principle, a molten salt bath or an oil bath at a finishing temperature (T3) above the starting temperature (T2) for a second period of time (Δtiso,2).
- Process according to Claim 1, characterized in that the austenitic microstructure of the steel parts is at least substantially transformed into an in particular purely bainitic microstructure.
- Process according to Claim 1, characterized in that the starting temperature (T2) used is a temperature of from 215°C to 230°C.
- Process according to Claim 1, characterized in that the finishing temperature (T3) used is a temperature of from 240°C to 280°C.
- Process according to at least one of the preceding claims, characterized in that the quenching in accordance with process step b.) and/or the holding in accordance with process step c.) is carried out in a first molten salt bath or oil bath.
- Process according to at least one of the preceding claims, characterized in that the second period of time (Δtiso,2) lasts for from 200 min to 400 min, in particular from 250 min to 300 min.
- Process according to at least one of the preceding claims, characterized in that after process step d.) the steel parts are cooled to a temperature (T4) of from 20°C to 40°C.
- Process according to at least one of the preceding claims, characterized in that the core hardness of the steel parts is set by means of the duration of the first and/or second period of time (Δtiso,1, Δtiso,2) and/or by means of the starting temperature (T2) and/or the finishing temperature (T3).
- Process according to at least one of the preceding claims, characterized in that the heat of reaction produced during the formation of the bainitic microstructure is at least partially utilized to heat the steel parts, in particular during process step d.), which is carried out in a furnace.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19963973A DE19963973C1 (en) | 1999-12-31 | 1999-12-31 | Production of bainite from steel parts comprises austenizing the parts, quenching to a starting temperature, isothermally storing the steel parts at the starting temperature and isothermally storing the parts at a finishing temperature |
| DE19963973 | 1999-12-31 | ||
| PCT/DE2000/003668 WO2001049888A1 (en) | 1999-12-31 | 2000-10-18 | Method for austempering steel parts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1248862A1 EP1248862A1 (en) | 2002-10-16 |
| EP1248862B1 true EP1248862B1 (en) | 2005-05-18 |
Family
ID=7935123
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP00984836A Revoked EP1248862B1 (en) | 1999-12-31 | 2000-10-18 | Method for austempering steel parts |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US6843867B1 (en) |
| EP (1) | EP1248862B1 (en) |
| JP (1) | JP5231700B2 (en) |
| AT (1) | ATE295901T1 (en) |
| DE (2) | DE19963973C1 (en) |
| WO (1) | WO2001049888A1 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102004038159B3 (en) * | 2004-08-06 | 2006-05-18 | Ab Skf | Process for the heat treatment of workpieces made of steel or cast iron |
| DE102007061084A1 (en) | 2007-12-19 | 2009-07-02 | Federal-Mogul Sealing Systems Gmbh | Metallic flat gasket and manufacturing process |
| US8066828B2 (en) * | 2008-06-18 | 2011-11-29 | Tata Consultancy Services, Ltd. | Method for efficient heat treatment of steel |
| JP2014516120A (en) * | 2011-05-25 | 2014-07-07 | アクティエボラゲット・エスコーエッフ | Heat treatment method for steel components |
| EP2982769A1 (en) * | 2014-08-06 | 2016-02-10 | Indexator Group AB | Austempered steel, method for producing it, component and semi-finished bad |
| DE102015218163A1 (en) | 2015-09-22 | 2017-03-23 | Robert Bosch Gmbh | Bainitized component and method of manufacture |
| US10822180B2 (en) | 2018-08-01 | 2020-11-03 | iwis drive systems, LLC | Chain for grain elevators |
| SE542672C2 (en) | 2018-09-14 | 2020-06-23 | Ausferritic Ab | Method for producing an ausferritic steel austempered during continuous cooling followed by annealing |
| US11713492B2 (en) | 2019-06-25 | 2023-08-01 | iwis drive systems, LLC | Offset link for roller chain with enhanced strength |
| DE102021130969A1 (en) | 2021-11-25 | 2023-05-25 | Ald Vacuum Technologies Gmbh | Process and system for bainitising metallic workpieces |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2258566A (en) * | 1940-07-30 | 1941-10-07 | American Steel & Wire Co | Hardenable steel heat treatment |
| DE2939380A1 (en) * | 1979-09-28 | 1981-04-16 | Aichelin GmbH, 7015 Korntal | Isothermal quenching tank for workpieces leaving hardening furnace - where workpieces are transferred from molten salt bath to hot air duct by conveyor belt |
| JPH02277715A (en) * | 1989-04-19 | 1990-11-14 | Aisin Takaoka Ltd | Heat treatment of flake graphite cast iron |
| JP2984889B2 (en) * | 1992-07-08 | 1999-11-29 | 新日本製鐵株式会社 | High carbon steel wire or steel wire excellent in wire drawability and method for producing the same |
| WO1994028187A1 (en) * | 1993-05-25 | 1994-12-08 | Nippon Steel Corporation | High-carbon steel rod wire or steel wire excellent in workability in wire drawing and process for producing the same |
| DE19521941C1 (en) * | 1995-06-07 | 1996-10-02 | Mannesmann Ag | Mfg. sintered air-hardenable alloy steel component |
| JP3580938B2 (en) * | 1996-03-05 | 2004-10-27 | アイシン・エィ・ダブリュ株式会社 | Heated bainite treatment method |
| SE510344C2 (en) * | 1997-08-01 | 1999-05-17 | Ovako Steel Ab | Way for complete bainite hardening of steel |
-
1999
- 1999-12-31 DE DE19963973A patent/DE19963973C1/en not_active Revoked
-
2000
- 2000-10-18 JP JP2001550415A patent/JP5231700B2/en not_active Expired - Lifetime
- 2000-10-18 EP EP00984836A patent/EP1248862B1/en not_active Revoked
- 2000-10-18 WO PCT/DE2000/003668 patent/WO2001049888A1/en active IP Right Grant
- 2000-10-18 US US10/169,444 patent/US6843867B1/en not_active Expired - Lifetime
- 2000-10-18 AT AT00984836T patent/ATE295901T1/en active
- 2000-10-18 DE DE50010362T patent/DE50010362D1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JP5231700B2 (en) | 2013-07-10 |
| WO2001049888A9 (en) | 2003-06-05 |
| DE50010362D1 (en) | 2005-06-23 |
| US6843867B1 (en) | 2005-01-18 |
| WO2001049888A1 (en) | 2001-07-12 |
| DE19963973C1 (en) | 2001-05-31 |
| JP2004510048A (en) | 2004-04-02 |
| EP1248862A1 (en) | 2002-10-16 |
| ATE295901T1 (en) | 2005-06-15 |
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