EP1248862A1 - Method for austempering steel parts - Google Patents
Method for austempering steel partsInfo
- Publication number
- EP1248862A1 EP1248862A1 EP00984836A EP00984836A EP1248862A1 EP 1248862 A1 EP1248862 A1 EP 1248862A1 EP 00984836 A EP00984836 A EP 00984836A EP 00984836 A EP00984836 A EP 00984836A EP 1248862 A1 EP1248862 A1 EP 1248862A1
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- EP
- European Patent Office
- Prior art keywords
- steel parts
- temperature
- period
- start temperature
- steel
- 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.)
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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
- C21D1/20—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 bainizing steel parts according to the preamble of the main claim.
- “Bainitizing” is understood to mean a heat treatment of steel, which first comprises “austenitizing” the steel, then quenching it to a temperature above the so-called “artsite” starting temperature, and maintaining the steel at this temperature for a predetermined time.
- the steel is quenched without interruption from the start of the bainite transformation (so-called bainite start) to the end of the bainite transformation (so-called bainite finish) at a constant temperature and a suitable, suitably chosen holding time in this salt bath stored.
- the steel to be bainitized into a holding furnace operated with circulating air after a defined dwell time in the salt hot bath in order to achieve a complete conversion of austenite into bainite.
- the holding furnace has the same temperature as the warm salt bath.
- the method according to the invention for bainitizing steel parts has the advantage over the prior art that an at least almost complete conversion of austenite into bainite, ie a purely bainitic structure, can be achieved, the hardness of which follows steel parts obtained can be controlled in a simple manner by the process parameters.
- the steel parts obtained have improved strength properties, for example with regard to a pulsating pressure-swell load.
- the method according to the invention can be used in a simple manner in series production without substantial interventions in existing production processes or investments in production plants being necessary.
- the process according to the invention further advantageously enables quenching of batches of steel parts at low salt bath temperatures while simultaneously producing as pure bainite as possible, ie without a proportion of continuous bainite, wherein a uniform quenching intensity is also achieved within one batch.
- the choice of the star temperature T 2 which is preferably a little above the martensite start temperature T M , advantageously prevents the pearlite microstructure region from being run through in the ZTU image when quenching.
- the core hardness of the steel parts obtained after carrying out the process according to the invention can be adjusted by the duration of the first period, ie by holding in the first salt bath or oil bath, and also the temperature of the first salt bath. It generally applies that the core hardness of the bainitic structure of the steel parts obtained is lower, the shorter the residence time in the first salt bath is selected.
- the same also advantageously applies to the transfer of the steel parts into a holding furnace according to the recirculating air principle or into a second salt bath at an elevated temperature during the second period.
- the core hardness of the obtained, preferably purely bainitic, structure is
- Steel parts are a function of the finish temperature and the duration of this second period.
- the resulting heat of reaction can also advantageously be used to convert the steel parts from a start temperature T 2 to a finish temperature after the end of the first period To heat T 3 , on which the steel parts are then held for the duration of the second period. This results in energy savings and quick and even heating of the steel parts.
- the figure shows a schematic diagram of a so-called “ZTU image” (time-temperature conversion diagram) of the conversion from austenite to bainite by means of a stepped bainite conversion.
- ZTU image time-temperature conversion diagram
- the invention is illustrated using the example of the bainitization of steel of type 100Cr6, material no. 1.3505.
- steel parts of this type are first austenitized in a manner known per se and then, starting from a quenching temperature T x of 830 ° C. to 870 ° C., for example 850 ° C., in a manner known per se in a first salt warm 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 H in the example explained is approximately 205 ° C to 215 ° C.
- Austenite microstructure region 15 is present and is quenched from the quenching temperature T- at a time t 0 within a period of typically 5 s to 15 s to the starting temperature T 2 .
- a first period then begins, which lasts over a period of time ⁇ t iso _ x , during which the steel or the steel parts in a first salt bath in a manner known per se at at least approximately constant starting temperature T 2 are kept.
- An oil bath can also be used instead of the salt bath.
- ZTU image 5 also shows that during the first time period ⁇ t iS0 / x, the austenite previously present in the austenite structure region 15 begins to convert to bainite. This start of the bainite conversion takes place as soon as the conversion curve 16 entered in the ZTU image shows the course over time of the one according to the invention
- the pearlite microstructure region 11 which is not passed through in the bainitization according to the invention by means of stepped thermal conversion, is also entered in the ZTU image 5.
- the steel parts are then at a finish temperature T 3 , which is above the start temperature T 2 lies, at least approximately isothermally.
- This second, isothermal storage at the finish temperature T 3 lasts over a second period of time ⁇ t is ⁇ 2 , the is complete as soon as the bainite structural region 12 is reached at time t 3 , ie as soon as an at least almost complete conversion of austenite into pure bainite has taken place.
- the time period ⁇ t iso _ 2 or the time t 3 can also be chosen or extended, deviating from the illustration in the figure and, for example, for reasons of process stability, that the coordinate (t 3 / T 3 ) lies within the bainite structure region 12. Reaching the boundary of the bainite microstructure region 12 in the figure during the second time period ⁇ t is ⁇ 2 is therefore only a minimum requirement for the length of the second
- the second, isothermal storage of the steel parts at the finishing temperature T 3 takes place, for example, in a second warm salt bath or oil bath or alternatively also in a holding furnace, for example a holding furnace according to the recirculating air principle.
- the steel parts obtained are then exited, cooled and cleaned in a known manner.
- the batch to be treated is first quenched in the first hot salt bath at a starting temperature T 2 of 215 ° C. to 230 ° C.
- T 2 a starting temperature of 215 ° C. to 230 ° C.
- a temperature of 220 ° C. is particularly preferred.
- the steel parts then become isothermal in the first warm salt bath for the first period ⁇ t iso _ ! stored, which lasts between 5 min and 30 min, preferably 20 min.
- the steel parts are transferred to a holding oven according to the recirculating air principle, which has a finishing temperature T 3 of 240 ° C. to 280 ° C., in particular 260 ° C.
- T 3 finishing temperature of 240 ° C. to 280 ° C., in particular 260 ° C.
- Finish temperature T 3 over the second period ⁇ t iBO / 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 be used instead of a holding furnace.
- a preferred embodiment of the method according to the invention further provides that the heat of reaction generated during the formation of the bainite structure is at least partially used for heating the steel parts from the starting temperature T 2 to the finishing temperature T 3 or for heating the holding furnace.
- the steel parts with a bainitic structure produced or treated by the explained method finally have a core hardness of 650 HV10 to 700 HV10, which is reduced compared to the starting material.
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- Heat Treatment Of Steel (AREA)
Abstract
A method of austempering of steel parts is described. The steel parts are initially austenitized and subsequently quenched to a start temperature which is higher than the martensite start temperature. Then the steel parts are subjected to a first isothermal holding at the start temperature for a first time period. Subsequently the steel parts are held for a second isothermal time period at a finish temperature which is higher than the start temperature. The method described is particularly well suited for rapid austempering of steel parts, a pure bainitic structure being achievable, and the core hardness of the steel parts obtained being settable via the start temperature, the finish temperature, the duration of the first time period, and the duration of the second time period.
Description
Verfahren zum Bainitisieren von StahlteilenProcess for bainitizing steel parts
Die Erfindung betrifft ein Verfahren zum Bainitisieren von Stahlteilen nach der Gattung des Hauptanspruehes .The invention relates to a method for bainizing steel parts according to the preamble of the main claim.
Stand der TechnikState of the art
Unter „Bainitisieren" versteht man eine Wärmebehandlung von Stahl, die zunächst ein „Austenitisieren" des Stahles, eine nachfolgende Abschreckung auf eine Temperatur oberhalb der sogenannten „ artensit"-Starttemperatur und ein Halten des Stahles auf dieser Temperatur über eine vorgegebene Zeit umfaßt ."Bainitizing" is understood to mean a heat treatment of steel, which first comprises "austenitizing" the steel, then quenching it to a temperature above the so-called "artensite" starting temperature, and maintaining the steel at this temperature for a predetermined time.
Mit dieser Vorgehensweise, die auch als „isothermischeWith this procedure, which is also called "isothermal
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.Conversion "from austenite to bainite, it is possible to obtain a steel which, depending on the objective and controllable via the temperature and holding time, has been completely or partially converted from an austenitic structure 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.With regard to further details on austenitizing and the explained bainitizing of steel, which have long been known per se, reference is made, for example, to E. Zimmermann, "Materials science and 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 bekannt.The austenitizing of steel, a subsequent quenching and the isothermal conversion of austenite into bainite above the martensite starting temperature is also known, for example, from US Pat. No. 5,628,045.
Die Bainitisierung von zuvor austenitisierten Stählen erfolgt bisher weiter vielfach in Bädern, sogenanntenThe bainitization of previously austenitized steels has so far often been carried out in so-called baths
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 ent- sprechenden, geeignet gewählten Haltezeit in diesem Salzwarmbad ohne Unterbrechung gelagert.Salt hot baths. For this purpose, the steel is quenched without interruption from the start of the bainite transformation (so-called bainite start) to the end of the bainite transformation (so-called bainite finish) at a constant temperature and a suitable, suitably chosen holding time in this salt bath stored.
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 also already been proposed to convert the steel to be bainitized into a holding furnace operated with circulating air after a defined dwell time in the salt hot bath in order to achieve a complete conversion of austenite into bainite. For this purpose, the holding furnace has the same temperature as the warm salt bath.
Vorteile der ErfindungAdvantages of the invention
Das erfindungsgemäße Verfahren zum Bainitisieren von Stahl- teilen 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 method according to the invention for bainitizing steel parts has the advantage over the prior art that an at least almost complete conversion of austenite into bainite, ie a purely bainitic structure, can be achieved, the hardness of which follows steel parts obtained can be controlled in a simple manner by the process parameters. In particular, the steel parts obtained have improved strength properties, for example with regard to a pulsating pressure-swell load.
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 the time required to convert austenite to bainite can be significantly reduced by the method according to the invention. This also results in considerable cost advantages when carrying out 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.It is also advantageous that the method according to the invention can be used in a simple manner in series production without substantial interventions in existing production processes or investments in production plants being necessary.
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 Star - 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 process according to the invention further advantageously enables quenching of batches of steel parts at low salt bath temperatures while simultaneously producing as pure bainite as possible, ie without a proportion of continuous bainite, wherein a uniform quenching intensity is also achieved within one batch. In particular, the choice of the star temperature T 2 , which is preferably a little above the martensite start temperature T M , advantageously prevents the pearlite microstructure region from being run through in the ZTU image when quenching.
Vorteilhafte Weiterbildungen der Erfindung ergeben sich aus den in den Unteransprüchen genannten Maßnahmen.
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.Advantageous developments of the invention result from the measures mentioned in the subclaims. It is advantageous that the core hardness of the steel parts obtained after carrying out the process according to the invention can be adjusted by the duration of the first period, ie by holding in the first salt bath or oil bath, and also the temperature of the first salt bath. It generally applies that the core hardness of the bainitic structure of the steel parts obtained is lower, the shorter the 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 derThe same also advantageously applies to the transfer of the steel parts into a holding furnace according to the recirculating air principle or into a second salt bath at an elevated temperature during the second period. In this case too, the core hardness of the obtained, preferably purely bainitic, structure is
Stahlteile eine Funktion der Finish-Temperatur und der Dauer dieses zweiten Zeitraumes .Steel parts are a function of the finish temperature and the duration of this second period.
Da es sich bei der Umwandlung eines Austenit-Gefüges in ein Bainit-Gefuge 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 the transformation of an austenite structure into a bainite structure is an exothermic reaction, the resulting heat of reaction can also advantageously be used to convert the steel parts from a start temperature T 2 to a finish temperature after the end of the first period To heat T 3 , on which the steel parts are then held for the duration of the second period. This results in energy savings and quick and even heating of the steel parts.
Zeichnung
Ausführungsbeispiele der Erfindung werden anhand der Zeichnung und in der nachfolgenden Beschreibung näher erläutert .drawing Embodiments of the invention are explained in more detail with reference to the drawing and in the description below.
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 diagram) of the conversion from austenite to bainite by means of a stepped bainite conversion.
Ausführungsbeispieleembodiments
Die Erfindung wird am Beispiel der Bainitisierung von Stahl des Typs 100Cr6, Werkstoff-Nr . 1.3505, erläutert.The invention is illustrated using the example of the bainitization of steel of type 100Cr6, material no. 1.3505.
Dazu werden zunächst Stahlteile dieses Typs in an sich bekannter Weise austenitisiert und danach ausgehend von einer Abschreck-Temperatur Tx 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 TH liegt im erläuterten Beispiel bei ca. 205°C bis 215°C.For this purpose, steel parts of this type are first austenitized in a manner known per se and then, starting from a quenching temperature T x of 830 ° C. to 870 ° C., for example 850 ° C., in a manner known per se in a first salt warm 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 H in the example explained is approximately 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 einemThis is explained with the aid of the figure, which shows in a ZTU picture 5 that the steel is initially in a form of austenite
Austenit-Gefügebereich 15 vorliegt, und zu einem Zeitpunkt t0 von der Abschreck-Temperatur T-, innerhalb eines Zeitraumes von typischerweise 5 s bis 15 s auf die Start- Temperatur T2 abgeschreckt wird. Zu dem Zeitpunkt t2 beginnt dann ein erster Zeitraum, der über eine Zeitdauer Δtiso_ x 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.Austenite microstructure region 15 is present and is quenched from the quenching temperature T- at a time t 0 within a period of typically 5 s to 15 s to the starting temperature T 2 . At time t 2 , a first period then begins, which lasts over a period of time Δt iso _ x , during which the steel or the steel parts in a first salt bath in a manner known per se at at least approximately constant starting temperature T 2 are kept. An oil bath can also be used instead of the salt bath.
In dem ZTU-Bild 5 ist weiter eingetragen, daß während des ersten Zeitraumes ΔtiS0/ x der zuvor in dem Austenit-Gefüge- bereich 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 erfindungsgemäßenZTU image 5 also shows that during the first time period Δt iS0 / x, the austenite previously present in the austenite structure region 15 begins to convert to bainite. This start of the bainite conversion takes place as soon as the conversion curve 16 entered in the ZTU image shows the course over time of the one according to the invention
Verfahren eingesetzten Temperatur darstellt, in den Bainit- umwandlungsbereich 13 eintritt .Represents the temperature used, enters the bainite conversion region 13.
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-Gefuge vorliegen.The transformation from austenite to bainite is completed as soon as the conversion curve reaches 16 in TTT chart 5 the bainitic structure region 12 in which the steel parts as pure • be bainite Gefuge.
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.In addition, the pearlite microstructure region 11, which is not passed through in the bainitization according to the invention by means of stepped thermal conversion, is also entered in the ZTU image 5.
Nachdem das isotherme Lagern der Stahlteile bei der Start- Temperatur T2 über den ersten Zeitraum Δtlsθι x 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 time period Δt lsθι x 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 lies, at least approximately isothermally.
Dieses zweite, isotherme Lagern bei der Finish-Temperatur T3 dauert über einen zweiten Zeitraum Δtisθι 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 Δtisθι 2 ist somit lediglich als Minimalerfordernis für die Länge des zweitenThis second, isothermal storage at the finish temperature T 3 lasts over a second period of time Δt isθι 2 , the is complete as soon as the bainite structural region 12 is reached at time t 3 , ie as soon as an at least almost complete conversion of austenite into pure bainite has taken place. It should be emphasized that the time period Δt iso _ 2 or the time t 3 can also be chosen or extended, deviating from the illustration in the figure and, for example, for reasons of process stability, that the coordinate (t 3 / T 3 ) lies within the bainite structure region 12. Reaching the boundary of the bainite microstructure region 12 in the figure during the second time period Δt isθι 2 is therefore only a minimum requirement for the length of the second
Zeitraumes ΔtiBO/ 2 zu verstehen.Period Δt iBO / 2 to understand.
Das zweite, isotherme Lagern der Stahlteile bei der Finish- Temperatur T3 erfolgt beispielsweise in einem zweiten Salzwarmbad oder Ölbad oder alternativ auch in einem Halteofen, beispielsweise einem Halteofen nach dem Umluftprinzip .The second, isothermal storage of the steel parts at the finishing temperature T 3 takes place, for example, in a second warm salt bath or oil bath or alternatively also in a holding furnace, for example a holding furnace according to the recirculating air principle.
Nach Abschuß der erläuterten gestuften Bainitumwandlung folgt dann in bekannter Weise die Ausfahrt, Kühlung und Reinigung der erhaltenen Stahlteile.After the step-by-step bainite transformation explained has been fired, the steel parts obtained are then exited, cooled and cleaned in a known manner.
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 the steel parts have been austenitized, the batch to be treated is first quenched in the first hot salt bath at a starting temperature T 2 of 215 ° C. to 230 ° C. A temperature of 220 ° C. is particularly preferred.
Bei dieser Start-Temperatur T2 werden die Stahlteile dann isotherm in dem ersten Salzwarmbad über den ersten Zeitraum
Δtiso_ ! gelagert, der zwischen 5 min und 30 min, bevorzugt 20 min, andauert .At this starting temperature T 2 , the steel parts then become isothermal in the first warm salt bath for the first period Δt iso _ ! stored, which lasts between 5 min and 30 min, preferably 20 min.
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 dieserThen, at time t 2, the steel parts are transferred to a holding oven according to the recirculating air principle, which has a finishing temperature T 3 of 240 ° C. to 280 ° C., in particular 260 ° C. The steel parts are then at this
Finish-Temperatur T3 über den zweiten Zeitraum ΔtiBO/ 2, der zwischen 200 min und 400 min, bevorzugt 250 min bis 270 min, andauert, gelagert.Finish temperature T 3 over the second period Δt iBO / 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, a second salt bath with the finishing temperature T 3 can be used instead of a holding furnace.
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 generated during the formation of the bainite structure is at least partially used for heating the steel parts from the starting temperature T 2 to the finishing temperature T 3 or for heating the holding furnace.
Insgesamt wird durch das erläuterte Verfahren eine deutlicheOverall, the process explained makes a clear one
Verkürzung der Gesamt-Bainitumwandlungszeit erreicht, die im erläuterten Ausführungsbeispiel nunmehr ca. 300 min beträgt.Shortening of the total bainite conversion time reached, which in the illustrated embodiment is now approximately 300 minutes.
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 Zeit- ersparnis von typischerweise ca. 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.Compared to known processes, ie the isothermal storage of the steel parts at the starting temperature T 2 until the pure bainite structure is reached, this results in a time saving of typically approx. 60 min. The steel parts with a bainitic structure produced or treated by the explained method finally have a core hardness of 650 HV10 to 700 HV10, which is reduced compared to the starting material.
Gleichzeitig ergab sich eine deutliche Festigkeitssteigerung der Stahlteile bei pulsierender Druck-Schwell-Belastung.
At the same time, there was a significant increase in the strength of the steel parts with pulsating pressure-swell loads.
Claims
1. Verfahren zum Bainitisieren von Stahlteilen, mit den Verfahrensschritten: a.) Austentisieren der Stahlteile, b.) Abschreckung der Stahlteile auf eine Start-Temperatur (T2) , die oberhalb der Martensit-Starttemperatur (TM) der Stahlteile liegt, c.) zumindest näherungsweise isothermes Lagern der Stahlteile bei der Start-Temperatur (T2) über einen ersten Zeitraum (Δtisθι und d.) zumindest näherungsweise isothermes Lagern der Stahlteile bei einer Finish-Temperatur (T3) oberhalb der Starttemperatur (T2) über einen zweiten Zeitraum (Δtisθ; 2) .1. A process for bainitizing steel parts, with the process steps: a.) Tenting the steel parts, b.) Quenching the steel parts to a start temperature (T 2 ) which is above the martensite start temperature (T M ) of the steel parts, c .) at least approximately isothermal storage of the steel parts at the start temperature (T 2 ) over a first period (Δt isθι and d.) at least approximately isothermal storage of the steel parts at a finish temperature (T 3 ) above the start temperature (T 2 ) over a second period (Δt isθ; 2 ).
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das austenitische Gefüge der Stahlteile zumindest weitgehend in ein insbesondere rein bainitisches Gefüge umgewandelt wird.2. The method according to claim 1, characterized in that the austenitic structure of the steel parts is at least largely converted into a particularly bainitic structure.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß als Start-Temperatur (T2) eine Temperatur von 215°C bis 230°C eingesetzt wird. 3. The method according to claim 1, characterized in that a temperature of 215 ° C to 230 ° C is used as the starting temperature (T 2 ).
4. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß als Finish-Temperatur (T3) eine Temperatur von 240°C bis 280°C eingesetzt wird.4. The method according to claim 1, characterized in that a temperature of 240 ° C to 280 ° C is used as the finishing temperature (T 3 ).
5. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß das Abschrecken gemäß Verfahrensschritt b.) und/oder das Lagern gemäß Verfahrensschritt c.) in einem ersten Salzwarmbad oder Ölbad erfolgt .5. The method according to at least one of the preceding claims, characterized in that the quenching according to process step b.) And / or the storage according to process step c.) Takes place in a first salt bath or oil bath.
6. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß das Lagern gemäß Verfahrensschritt d.) in einem Ofen, insbesondere einem Umluftofen, oder einem zweiten Salzwarmbad oder Ölbad erfolgt .6. The method according to at least one of the preceding claims, characterized in that the storage according to step d.) In an oven, in particular a forced air oven, or a second salt bath or oil bath.
7. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß der erste Zeitraum7. The method according to at least one of the preceding claims, characterized in that the first period
(Δtiso, über 5 Minuten bis 30 min andauert.(Δt iso, lasts from 5 minutes to 30 minutes.
8. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß der zweite Zeitraum8. The method according to at least one of the preceding claims, characterized in that the second period
(Δtisθ/ 2) über 200 min bis 400 min, insbesondere 250 min bis 300 min, andauert.(Δt isθ / 2 ) over 200 min to 400 min, in particular 250 min to 300 min.
9. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß nach dem Verfahrensschritt d.) eine Kühlung der Stahlteile auf eine Temperatur (T4) von 20°C bis 40°C erfolgt.9. The method according to at least one of the preceding claims, characterized in that after step d.) Cooling of the steel parts to a temperature (T 4 ) of 20 ° C to 40 ° C takes place.
10. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die Kernhärte der Stahlteile über die Dauer des ersten und/oder zweiten10. The method according to at least one of the preceding claims, characterized in that the core hardness of Steel parts over the duration of the first and / or second
Zeitraumes (ΔtiBO/ x, Δtlsθ/ 2) und/oder über die Start- Temperatur (T2) und/oder die Finish-Temperatur (T3) eingestellt wird.Period (Δt iBO / x , Δt lsθ / 2 ) and / or via the start temperature (T 2 ) and / or the finish temperature (T 3 ) is set.
11. Verfahren nach mindestens einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die bei der Bildung des bainitischen Gefüges entstehende Reaktionswärme zumindest teilweise zur Erwärmung der Stahlteile, insbesondere während des in einem Ofen durchgeführten Verfahresschrittes d.), genutzt wird. 11. The method according to at least one of the preceding claims, characterized in that the heat of reaction arising during the formation of the bainitic structure is used at least partially for heating the steel parts, in particular during the process step d.) Carried out in an oven.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19963973 | 1999-12-31 | ||
| 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 |
| PCT/DE2000/003668 WO2001049888A1 (en) | 1999-12-31 | 2000-10-18 | Method for austempering steel parts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1248862A1 true EP1248862A1 (en) | 2002-10-16 |
| EP1248862B1 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) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102007061084A1 (en) | 2007-12-19 | 2009-07-02 | Federal-Mogul Sealing Systems Gmbh | Metallic flat gasket and manufacturing process |
Families Citing this family (9)
| 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 |
| US8066828B2 (en) * | 2008-06-18 | 2011-11-29 | Tata Consultancy Services, Ltd. | Method for efficient heat treatment of steel |
| WO2012161635A1 (en) | 2011-05-25 | 2012-11-29 | Aktiebolaget Skf | Method for heat treating a steel component |
| 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 |
| DE69427473T2 (en) | 1993-05-25 | 2002-04-18 | Nippon Steel Corp | HIGH-CARBON STEEL ROD OR WIRE WITH EXCELLENT DRAWNABILITY AND METHOD FOR THE PRODUCTION THEREOF |
| 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 AT AT00984836T patent/ATE295901T1/en active
- 2000-10-18 WO PCT/DE2000/003668 patent/WO2001049888A1/en active IP Right Grant
- 2000-10-18 EP EP00984836A patent/EP1248862B1/en not_active Revoked
- 2000-10-18 JP JP2001550415A patent/JP5231700B2/en not_active Expired - Lifetime
- 2000-10-18 US US10/169,444 patent/US6843867B1/en not_active Expired - Lifetime
- 2000-10-18 DE DE50010362T patent/DE50010362D1/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| See references of WO0149888A1 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102007061084A1 (en) | 2007-12-19 | 2009-07-02 | Federal-Mogul Sealing Systems Gmbh | Metallic flat gasket and manufacturing process |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5231700B2 (en) | 2013-07-10 |
| US6843867B1 (en) | 2005-01-18 |
| WO2001049888A1 (en) | 2001-07-12 |
| JP2004510048A (en) | 2004-04-02 |
| ATE295901T1 (en) | 2005-06-15 |
| EP1248862B1 (en) | 2005-05-18 |
| DE19963973C1 (en) | 2001-05-31 |
| DE50010362D1 (en) | 2005-06-23 |
| WO2001049888A9 (en) | 2003-06-05 |
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