EP0503326A2 - Process for preparing a sintered article from steel powder - Google Patents
Process for preparing a sintered article from steel powder Download PDFInfo
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- EP0503326A2 EP0503326A2 EP92102793A EP92102793A EP0503326A2 EP 0503326 A2 EP0503326 A2 EP 0503326A2 EP 92102793 A EP92102793 A EP 92102793A EP 92102793 A EP92102793 A EP 92102793A EP 0503326 A2 EP0503326 A2 EP 0503326A2
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- temperature
- steel powder
- sintered body
- sintering
- carbon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
- B22F3/101—Changing atmosphere
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
- C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
- C22C33/0285—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with Cr, Co, or Ni having a minimum content higher than 5%
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2201/00—Treatment under specific atmosphere
- B22F2201/01—Reducing atmosphere
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2201/00—Treatment under specific atmosphere
- B22F2201/04—CO or CO2
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2201/00—Treatment under specific atmosphere
- B22F2201/10—Inert gases
Definitions
- the invention is based on a method for producing a carbon-containing sintered body from steel powder, in which the steel powder is heated to sintering temperature in an atmosphere which at least temporarily contains carbon monoxide, is kept at sintering temperature for a predetermined period of time, and the sintered body formed in this way is subsequently cooled.
- the invention relates to a state of the art, as specified for example in Metals Handbook Ninth Edition Vol 7 Powder Metallurgy, pp. 360 and 361.
- a method for producing a sintered body is described in which steel powder is mixed with graphite powder and the resulting powder mixture is subsequently sintered.
- the graphite should do two things: on the one hand, it should be in the steel powder Reduce metal oxides, on the other hand, it should diffuse into the steel powder in order to bring the carbon content of the sintered body to a predetermined value. This is necessary, since otherwise the steel powder is considerably decarburized in the atmosphere which acts during sintering, which is often vacuum or contains an inert gas.
- the carbon in the steel powder escapes by reacting with oxygen from or on the grains of the steel powder or from the atmosphere to form carbon monoxide, which is generally flushed away or pumped away with the atmosphere.
- carbon monoxide which is generally flushed away or pumped away with the atmosphere.
- an extremely homogeneous and finely divided mixture of steel and graphite powder is required. This requires complex technology and can hardly be checked for the degree of distribution in a production process geared towards series production for the purposes of quality control.
- the invention is based on the object of specifying a method of the type mentioned at the beginning with which the carbon content of the sintered bodies produced thereafter can be adjusted in a simple manner suitable for series production.
- the method according to the invention is characterized in that, by means of comparatively simple technological measures, sintered bodies based on a steel powder with - for example, the starting steel powder corresponding - carbon content can be produced.
- the method according to the invention ensures a largely constant good quality of the sintered bodies produced thereafter and can be used particularly advantageously in the production of series products because of the cost advantages resulting therefrom and at the same time high reliability.
- an X20CrMoV121 steel powder is used as the starting material for producing sintered bodies.
- the chemical composition of this steel powder is: Percentage by weight component 0.21 C. 11.6 Cr 1.08 Mon 0.30 V 0.58 Mn 0.38 Ni 0.36 Si rest Fe
- the structure of this starting material is predominantly martensitic with smaller proportions of ⁇ -ferrite and austenite.
- the particle size of the powder grains determined by sieving is less than 50 ⁇ m.
- the oxygen content inside the powder is 55ppm and has both dissolved Oxygen as well as oxides. Added to this are oxides and adsorbed oxygen on the surface of the powder from 100-1000ppm.
- steel powders can also be used in the production of sintered bodies by the method according to the invention.
- 50g powder are each filled into cuboid shapes of approx. 10mm x 15mm x 10mm.
- the filled molds are placed in a sintering furnace provided with an aluminum oxide tube with a diameter of approx. 50mm.
- a sintering gas under atmospheric pressure is fed to the furnace at an inflow rate of approximately 0.5 1 / min.
- the loaded with the filled molds furnace is / are heated at a rate of about 10 o C min to a sintering temperature of about 1330 o C, left for about one hour to the sintering temperature, and thereafter at a rate of about 10 o C / min to Cooled to room temperature.
- an inert gas such as argon in particular, is first fed to the furnace as the sintering gas.
- a gas change takes place above a temperature of preferably approximately 1000 ° C.
- the sinter gas now supplied has at least carbon monoxide in addition to the inert gas.
- the steel powder is carburized at a temperature below about 1200 o C.
- Decarburization takes place above a temperature of approx. 1200 o C.
- the sintered bodies formed cool down at a temperature of approximately 1200 ° C. renewed change of the sintered gas. Below this temperature, only inert gas, such as argon, is again supplied. This avoids carburization of the sintered bodies following the decarburization previously carried out.
- inert gas such as argon
- the carbon content of the sintered bodies can be adjusted to a predetermined value which deviates from the carbon content of the steel powder by shifting one or both temperatures.
- the composition of the sintering gas can not only be changed step by step, as described above, but also continuously during the execution of the manufacturing process in order to adjust the carbon content to the predetermined value.
- the carbon content of the sintered body to be produced can be determined particularly precisely, since this then ensures compliance with the predetermined one Carbon content and the balance defined by the ratio of the partial pressures of carbon monoxide to carbon dioxide can be maintained by continuously changing the partial pressure of the carbon monoxide throughout the entire production process.
- the carbon monoxide content - as described above - is gradually changed, it is advisable to switch from the inert gas to a sintering gas containing carbon monoxide during heating at a temperature between 900 and 1200 oC.
- a switchover temperature of approx. 1000 o C and cooling of approx. 1200 o C has proven to be particularly favorable .
- the manufacturing process is carried out in a closed container.
- the sintering process is timed in such a way that carbon oxides formed in the steel powder at high temperatures are decomposed on cooling and carbon which is produced is reinstalled in the sintered body.
- the production method can also be carried out in a container in which the steel powder and thus also the sintered body to be produced are surrounded by elemental carbon, such as preferably graphite. It is necessary for the graphite to be in relatively close contact with the steel powder or the sintered body.
- the oxygen residue of the sintered gas then fetches the carbon required to build up a carbon monoxide-containing atmosphere localized around the sintered body and influences the carbon content of the steel powder or the sintered body only insignificantly.
- the steel powder be heat-treated in a reducing atmosphere before the sintering process. If such a heat treatment is carried out at temperatures of up to 1400 ° C., the oxygen present in the metal oxides of the steel powder, which are hardly avoidable or attached to the powder particles, is largely removed by reaction with the reducing component of the atmosphere. In the subsequent sintering process, this oxygen can no longer contribute to decarburization of the steel powder with the formation of carbon monoxide.
- a steel powder preheated in this way can be set to a predetermined carbon content much more easily in the subsequent sintering process than a steel powder which has not been heat-treated since Preheating one of the factors influencing the carbon content of the sintered body is switched off.
- the proportions of easily reducible oxides such as FeO and / or Cr2O3, are considerably reduced even at temperatures above 800 to 1000 o C.
- oxides that are difficult to reduce, such as MnO are reduced to a minimum by, for example, sulfur binding.
Abstract
Das Verfahren dient der Herstellung eines kohlenstoffhaltigen Sinterkörpers aus Stahlpulver. Bei diesem Verfahren wird das Stahlpulver in einer zumindest zeitweise Kohlenmonoxid enthaltenden Atmosphäre auf Sintertemperatur erwärmt, über einen vorbestimmten Zeitraum auf Sintertemperatur gehalten und der hierbei gebildete Sinterkörper nachfolgend abgekühlt. Bei diesem Verfahren soll der Kohlenstoffgehalt des herzustellenden Sinterkörpers in einfacher und in für eine Serienfertigung geeigneter Weise auf einen vorgegebenen Wert eingestellt werden. Dies wird dadurch erreicht, dass der Partialdruck des in der Atmosphäre befindlichen Kohlenmonoxids während der Ausführung des Herstellverfahrens gezielt verändert wird, und dass diese Änderung derart gesteuert wird, dass der Kohlenstoffgehalt des Sinterkörpers nach Ausführung des Herstellverfahrens auf den vorbestimmten Wert eingestellt ist.The process is used to produce a carbon-containing sintered body from steel powder. In this method, the steel powder is heated to the sintering temperature in an atmosphere which at least temporarily contains carbon monoxide, is kept at the sintering temperature for a predetermined period of time and the sintered body formed in the process is subsequently cooled. In this method, the carbon content of the sintered body to be produced is to be set to a predetermined value in a simple manner that is suitable for series production. This is achieved in that the partial pressure of the carbon monoxide in the atmosphere is changed in a targeted manner during the execution of the production process, and in that this change is controlled in such a way that the carbon content of the sintered body is set to the predetermined value after the production process has been carried out.
Description
Bei der Erfindung wird ausgegangen von einem Verfahren zur Herstellung eines kohlenstoffhaltigen Sinterkörpers aus Stahlpulver, bei dem das Stahlpulver in einer zumindest zeitweise Kohlenmonoxid enthaltenden Atmosphäre auf Sintertemperatur erwärmt, über einen vorbestimmten Zeitraum auf Sintertemperatur gehalten, und der hierbei gebildete Sinterkörper nachfolgend abgekühlt wird.The invention is based on a method for producing a carbon-containing sintered body from steel powder, in which the steel powder is heated to sintering temperature in an atmosphere which at least temporarily contains carbon monoxide, is kept at sintering temperature for a predetermined period of time, and the sintered body formed in this way is subsequently cooled.
Die Erfindung nimmt dabei Bezug auf einen Stand der Technik, wie er beispielsweise in Metals Handbook Ninth Edition Vol 7 Powder Metallurgy, S.360 und 361, angegeben ist. In diesem Stand der Technik wird ein Verfahren zur Herstellung eines Sinterkörpers beschrieben, bei dem Stahlpulver mit Graphitpulver gemischt und die resultierende Pulvermischung nachfolgend gesintert wird. Hierbei soll der Graphit zweierlei bewirken: zum einen soll er im Stahlpulver befindliche Metalloxide reduzieren, zum anderen soll er in das Stahlpulver diffundieren, um so den Kohlenstoffgehalt des Sinterkörpers auf einen vorbestimmten Wert zu bringen. Dies ist notwendig, da andernfalls in der beim Sintern wirkenden Atmosphäre, welche häufig Vakuum ist oder ein inertes Gas enthält, eine erhebliche Entkohlung des Stahlpulvers erfolgt. Bei dieser Entkohlung entweicht der im Stahlpulver befindliche Kohlenstoff, indem er mit Sauerstoff etwa aus oder auf den Körnern des Stahlpulvers oder aus der Atmosphäre zu Kohlenmonoxid reagiert, welches im allgemeinen mit der Atmosphäre weggespült oder weggepumpt wird. Um eine solche Entkohlung zu vermeiden, ist eine äusserst homogene und fein verteilte Mischung von Stahl- und Graphitpulver erforderlich. Dies bedingt eine aufwendige Technologie und ist in einem auf Serienfertigung ausgerichteten Herstellverfahren zu Zwecken einer Qualitätskontrolle kaum auf den Verteilungsgrad hin zu prüfen.The invention relates to a state of the art, as specified for example in Metals Handbook Ninth Edition Vol 7 Powder Metallurgy, pp. 360 and 361. In this prior art, a method for producing a sintered body is described in which steel powder is mixed with graphite powder and the resulting powder mixture is subsequently sintered. Here, the graphite should do two things: on the one hand, it should be in the steel powder Reduce metal oxides, on the other hand, it should diffuse into the steel powder in order to bring the carbon content of the sintered body to a predetermined value. This is necessary, since otherwise the steel powder is considerably decarburized in the atmosphere which acts during sintering, which is often vacuum or contains an inert gas. During this decarburization, the carbon in the steel powder escapes by reacting with oxygen from or on the grains of the steel powder or from the atmosphere to form carbon monoxide, which is generally flushed away or pumped away with the atmosphere. In order to avoid such decarburization, an extremely homogeneous and finely divided mixture of steel and graphite powder is required. This requires complex technology and can hardly be checked for the degree of distribution in a production process geared towards series production for the purposes of quality control.
Der Erfindung, wie sie in Patentanspruch 1 definiert ist, liegt die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art anzugeben, mit dem in einfacher und in für eine Serienfertigung geeigneter Weise der Kohlenstoffgehalt der danach hergestellten Sinterkörper eingestellt werden kann.The invention, as defined in claim 1, is based on the object of specifying a method of the type mentioned at the beginning with which the carbon content of the sintered bodies produced thereafter can be adjusted in a simple manner suitable for series production.
Das Verfahren nach der Erfindung zeichnet sich dadurch aus, dass durch vergleichsweise einfach auszuführende technologische Massnahmen Sinterkörper auf der Basis eines Stahlpulvers mit einem - etwa dem Ausgangsstahlpulver entsprechenden - Kohlenstoffgehalt hergestellt werden können. Das Verfahrens nach der Erfindung gewährleistet eine weitgehend gleichbleibend gute Qualität der danach hergestellten Sinterkörper und lässt sich vor allem bei der Fertigung von Serienprodukten wegen der hieraus sich ergebenden Kostenvorteile bei gleichzeitig hoher Zuverlässigkeit mit besonderem Vorteil einsetzen.The method according to the invention is characterized in that, by means of comparatively simple technological measures, sintered bodies based on a steel powder with - for example, the starting steel powder corresponding - carbon content can be produced. The method according to the invention ensures a largely constant good quality of the sintered bodies produced thereafter and can be used particularly advantageously in the production of series products because of the cost advantages resulting therefrom and at the same time high reliability.
Nachfolgend werden bevorzugte Ausführungsbeispiele der Erfindung beschrieben. Bei diesen Ausführungsbeispielen wird als Ausgangsmaterial zur Herstellung von Sinterkörpern ein X20CrMoV121 - Stahlpulver verwendet. Die chemische Zusammensetzung dieses Stahlpulvers beträgt:
Die Struktur dieses Ausgangsmaterials ist überwiegend martensitisch mit kleineren Anteilen an δ-Ferrit und Austenit. Die durch Sieben bestimmte Teilchengrösse der Pulverkörner ist kleiner 50µm. Der Sauerstoffgehalt im Inneren des Pulvers beträgt 55ppm und weist sowohl gelösten Sauerstoff als auch Oxide auf. Hinzukommen Oxide und adsorbierter Sauerstoff auf der Oberfläche des Pulvers von 100-1000ppm.The structure of this starting material is predominantly martensitic with smaller proportions of δ-ferrite and austenite. The particle size of the powder grains determined by sieving is less than 50 μm. The oxygen content inside the powder is 55ppm and has both dissolved Oxygen as well as oxides. Added to this are oxides and adsorbed oxygen on the surface of the powder from 100-1000ppm.
Anstelle eines derartigen Stahlpulvers lassen sich auch andere Stahlpulver bei der Herstellung von Sinterkörpern nach dem erfindungsgemässen Verfahren verwenden.Instead of such a steel powder, other steel powders can also be used in the production of sintered bodies by the method according to the invention.
50g Pulver werden jeweils in quaderförmige Formen von ca 1oomm x 15mm x 10mm Abmessung gefüllt. Die gefüllten Formen werden in einen mit einer Aluminiumoxid- Röhre von ca. 50mm Durchmesser versehenen Sinterofen gebracht. Dem Ofen wird ein unter atmosphärischem Druck stehendes Sintergas mit einer Zuflussrate von ca. 0.5 1/min zugeführt.50g powder are each filled into cuboid shapes of approx. 10mm x 15mm x 10mm. The filled molds are placed in a sintering furnace provided with an aluminum oxide tube with a diameter of approx. 50mm. A sintering gas under atmospheric pressure is fed to the furnace at an inflow rate of approximately 0.5 1 / min.
Der mit den gefüllten Formen beschickte Ofen wird mit einer Rate von ca 10oC/min auf eine Sintertemperatur von ca. 1330oC aufgeheizt, ca. eine Stunde auf Sintertemperatur belassen und danach mit einer Rate von ca. 10oC/min auf Raumtemperatur abgekühlt.The loaded with the filled molds furnace is / are heated at a rate of about 10 o C min to a sintering temperature of about 1330 o C, left for about one hour to the sintering temperature, and thereafter at a rate of about 10 o C / min to Cooled to room temperature.
Beim Aufheizen wird dem Ofen als Sintergas zunächst ein Inertgas, wie insbesondere etwa Argon, zugeführt.When heating up, an inert gas, such as argon in particular, is first fed to the furnace as the sintering gas.
Oberhalb einer Temperatur von vorzugsweise ca. 1000oC findet ein Gaswechsel statt. Das nunmehr zugeführte Sintergas weist neben dem Inertgas zusätzlich zumindest noch Kohlenmonoxid auf. Hierdurch wird unterhalb einer Temperatur von ca.1200oC das Stahlpulvers aufgekohlt. Oberhalb einer Temperatur von ca. 1200oC findet eine Entkohlung statt.A gas change takes place above a temperature of preferably approximately 1000 ° C. The sinter gas now supplied has at least carbon monoxide in addition to the inert gas. Thereby, the steel powder is carburized at a temperature below about 1200 o C. Decarburization takes place above a temperature of approx. 1200 o C.
Nach der Sinterung wird beim Abkühlen der gebildeten Sinterkörper bei einer Temperatur von ca. 1200oC ein erneuter Wechsel des Sintergases vorgenommen. Unterhalb dieser Temperatur wird wiederum nurmehr Inertgas, wie etwa Argon, zugeführt. Hierdurch wird eine der zuvor vorgenommenen Entkohlung folgende Aufkohlung der Sinterkörper vermieden. Durch geeignete Wahl der Temperaturen, an denen die beiden Gaswechsel vorgenommen werden, kann so erreicht werden, dass in dem durch diese Temperaturen bestimmten Temperaturintervall die Auf- und die Entkohlung des Stahlpulvers und der daraus gebildeten Sinterkörper zur Gleichheit gebracht sind.After sintering, the sintered bodies formed cool down at a temperature of approximately 1200 ° C. renewed change of the sintered gas. Below this temperature, only inert gas, such as argon, is again supplied. This avoids carburization of the sintered bodies following the decarburization previously carried out. By a suitable choice of the temperatures at which the two gas changes are carried out, it can be achieved that the carburization and decarburization of the steel powder and the sintered bodies formed therefrom are brought into equality in the temperature interval determined by these temperatures.
Unter Beibehaltung der vor allem durch Sinterdauer sowie Aufheiz- und Abkühlrate bestimmten Verfahrensparameter kann durch Verlagerung einer oder beider Temperaturen der Kohlenstoffgehalt der Sinterkörper auf einen vom Kohlenstoffgehalt des Stahlpulvers abweichenden vorbestimmten Wert eingestellt werden.While maintaining the process parameters determined primarily by the sintering time and the heating and cooling rate, the carbon content of the sintered bodies can be adjusted to a predetermined value which deviates from the carbon content of the steel powder by shifting one or both temperatures.
Wichtig ist vor allem, dass der Partialdruck der den Sinterkörper bei der Ausführung des Herstellverfahrens umgebenden Atmosphäre gezielt verändert wird, und dass diese Änderung derart gesteuert wird, dass der Kohlenstoffgehalt des Sinterkörpers auf den vorbestimmten Wert eingestellt wird.It is particularly important that the partial pressure of the atmosphere surrounding the sintered body when the manufacturing process is carried out is changed in a targeted manner, and that this change is controlled in such a way that the carbon content of the sintered body is adjusted to the predetermined value.
Wird als Atmosphäre das Sintergas eingesetzt, so kann zur Einstellung des Kohlenstoffgehaltes auf den vorbestimmten Wert die Zusammensetzung des Sintergases während der Ausführung des Herstellverfahrens nicht nur - wie zuvor beschrieben - schrittweise, sondern auch kontinuierlich geändert werden. Hierbei lässt sich der Kohlenstoffgehalt des herzustellenden Sinterkörpers besonders genau festlegen, da dann das für die Einhaltung des vorbestimmten Kohlenstoffgehalts massgebliche und durch das Verhältnis der Partialdrücke von Kohlenmonoxid und Kohlendioxid definierte Gleichgewicht durch kontinuierliche Änderung des Partialdruckes des Kohlenmonoxids während des gesamten Herstellverfahrens eingehalten werden kann.If the sintering gas is used as the atmosphere, the composition of the sintering gas can not only be changed step by step, as described above, but also continuously during the execution of the manufacturing process in order to adjust the carbon content to the predetermined value. In this case, the carbon content of the sintered body to be produced can be determined particularly precisely, since this then ensures compliance with the predetermined one Carbon content and the balance defined by the ratio of the partial pressures of carbon monoxide to carbon dioxide can be maintained by continuously changing the partial pressure of the carbon monoxide throughout the entire production process.
Wird der Kohlenmonoxidgehalt - wie zuvor beschrieben - schrittweise verändert, so empfiehlt es sich, während des Aufheizens bei einer Temperatur zwischen 900 und 1200oC vom Inertgas auf ein kohlenmonoxidhaltiges Sintergas umzuschalten. Bei den zuvor angegebenen Parametern, wie Pulverzusammensetzung, Grösse der zu erstellenden Sinterkörper, Aufheiz- und Abkühlraten sowie Sinterdauer, hat sich während des Aufheizens eine Umschalttemperatur von ca. 1000oC und beim Abkühlen eine solche von ca. 1200oC als besonders günstig herausgestellt.If the carbon monoxide content - as described above - is gradually changed, it is advisable to switch from the inert gas to a sintering gas containing carbon monoxide during heating at a temperature between 900 and 1200 oC. With the parameters specified above, such as powder composition, size of the sintered body to be produced, heating and cooling rates and sintering time, a switchover temperature of approx. 1000 o C and cooling of approx. 1200 o C has proven to be particularly favorable .
Dem Sintergas werden während des Aufheizens beim Erreichen der Umschalttemperatur bis zu 10 Volumenprozent Kohlenmonoxid zugeführt. Es ist zu empfehlen, dem Sintergas beim Erreichen der Umschalttemperatur zusätzlich ein reduzierendes Gas, wie vorzugsweise Wasserstoff, zuzugeben. Hierdurch wird zusätzlich erreicht, dass bei der durch das Kohlenmonoxid bewirkten Aufkohlung des Sinterkörpers dessen Oxidation weitgeheng vermieden wird. Dies ist von besonderem Vorteil bei der Herstellung vergleichsweise poröser und/oder mit einer Pulverfüllung versehener Sinterkörper. Dem Sintergas können bis zu 20 Volumenprozent Wasserstoff zugeführt werden. Sehr bewährt hat es sich, während des Aufheizens beim Erreichen der Umschalttemperatur ein Sintergas mit ca. 5 Volumenprozent Kohlenmonoxid und ca. 10 Volumenprozent Wasserstoff zuzuführen.Up to 10 percent by volume of carbon monoxide is added to the sintered gas during heating when the switchover temperature is reached. It is recommended to add a reducing gas, such as preferably hydrogen, to the sintering gas when the changeover temperature is reached. This additionally ensures that the carbonization of the sintered body caused by the carbon monoxide largely avoids its oxidation. This is of particular advantage in the production of comparatively porous and / or sintered bodies provided with a powder filling. Up to 20 percent by volume of hydrogen can be added to the sintering gas. It has proven very useful to add a sintering gas with approx. 5 percent by volume carbon monoxide and approx. 10 percent by volume hydrogen during heating when the changeover temperature is reached.
Es ist möglich, das Herstellverfahren in einem abgeschlossenen Behälter auszuführen. Hierbei wird der Sintervorgang zeitlich derart gesteuert, dass bei hohen Temperaturen im Stahlpulver gebildete Kohlenstoffoxide beim Abkühlen zersetzt werden und dabei entstehender Kohlenstoff in den Sinterkörper wieder eingebaut wird.It is possible to carry out the manufacturing process in a closed container. In this case, the sintering process is timed in such a way that carbon oxides formed in the steel powder at high temperatures are decomposed on cooling and carbon which is produced is reinstalled in the sintered body.
Ferner kann das Herstellverfahren auch in einem Behälter ausgeführt werden, in dem das Stahlpulver und damit auch der herzustellende Sinterkörper von elementarem Kohlenstoff, wie vorzugsweise Graphit, umgeben ist. Hierbei ist es erforderlich, dass der Graphit in relativ engem Kontakt mit dem Stahlpulver bzw. dem Sinterkörper steht. Der Sauerstoffrest des Sintergases holt sich dann den zum Aufbau einer um den Sinterkörper lokalisierten, kohlenmonoxidhaltigen Atmosphäre benötigten Kohlenstoff aus der Graphithülle und beeinflusst den Kohlenstoffgehalt des Stahlpulvers bzw. des Sinterkörpers nurmehr unwesentlich.Furthermore, the production method can also be carried out in a container in which the steel powder and thus also the sintered body to be produced are surrounded by elemental carbon, such as preferably graphite. It is necessary for the graphite to be in relatively close contact with the steel powder or the sintered body. The oxygen residue of the sintered gas then fetches the carbon required to build up a carbon monoxide-containing atmosphere localized around the sintered body and influences the carbon content of the steel powder or the sintered body only insignificantly.
Es ist sehr zu empfehlen, vor dem Sinterprozess eine Wärmebehandlung des Stahlpulvers in einer reduzierenden Atmosphäre vorzunehmen. Wird eine solche Wärmebehandlung bei Temperaturen bis zu 1400oC durchgeführt, so wird der in den kaum zu vermeidenden Metalloxiden des Stahlpulvers befindliche oder an den Pulverteilchen angelagerte Sauerstoff durch Reaktion mit dem reduzierenden Bestandteil der Atmosphäre weitgehend entfernt. Im nachfolgenden Sinterprozess kann dieser Sauerstoff dann nicht mehr zu einer Entkohlung des Stahlpulvers unter Bildung von Kohlenmonoxid beitragen. Ein derart vorgeglühtes Stahlpulver kann im nachfolgenden Sinterprozess wesentlich einfacher auf einen vorbestimmten Kohlenstoffgehalt eingestellt werden als ein nicht wärmebehandeltes Stahlpulver, da durch das Vorglühen einer der den Kohlenstoffgehalt des Sinterkörpers beeinflussenden Faktoren ausgeschaltet ist.
Wird das Stahlpulver in einer Wasserstoffatmosphäre geglüht, so werden bereits schon bei Temperaturen oberhalb 800 bis 1000oC die Anteile an leicht reduzierbaren Oxiden, wie z.B. FeO und/oder Cr₂O₃, erheblich reduziert. Hingegen werden schwer reduzierbare Oxide, wie z.B. MnO, etwa durch Schwefelabbindung auf ein Minimum reduziert.It is highly recommended that the steel powder be heat-treated in a reducing atmosphere before the sintering process. If such a heat treatment is carried out at temperatures of up to 1400 ° C., the oxygen present in the metal oxides of the steel powder, which are hardly avoidable or attached to the powder particles, is largely removed by reaction with the reducing component of the atmosphere. In the subsequent sintering process, this oxygen can no longer contribute to decarburization of the steel powder with the formation of carbon monoxide. A steel powder preheated in this way can be set to a predetermined carbon content much more easily in the subsequent sintering process than a steel powder which has not been heat-treated since Preheating one of the factors influencing the carbon content of the sintered body is switched off.
If the steel powder is annealed in a hydrogen atmosphere, the proportions of easily reducible oxides, such as FeO and / or Cr₂O₃, are considerably reduced even at temperatures above 800 to 1000 o C. In contrast, oxides that are difficult to reduce, such as MnO, are reduced to a minimum by, for example, sulfur binding.
Claims (13)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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CH76291 | 1991-03-13 | ||
CH762/91 | 1991-03-13 |
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EP0503326A2 true EP0503326A2 (en) | 1992-09-16 |
EP0503326A3 EP0503326A3 (en) | 1993-06-30 |
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Application Number | Title | Priority Date | Filing Date |
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EP19920102793 Ceased EP0503326A3 (en) | 1991-03-13 | 1992-02-20 | Process for preparing a sintered article from steel powder |
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US (1) | US5162099A (en) |
EP (1) | EP0503326A3 (en) |
JP (1) | JPH0625710A (en) |
DE (1) | DE4113928A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1998053939A1 (en) * | 1997-05-27 | 1998-12-03 | Höganäs Ab | Method of monitoring and controlling the composition of sintering atmosphere |
WO1999037425A1 (en) * | 1998-01-21 | 1999-07-29 | Höganäs Ab | Process of preparing an iron-based powder in a gas-tight furnace |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
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JPH04208512A (en) * | 1990-11-30 | 1992-07-30 | Nec Corp | Manufacture of solid electrolytic capacitor |
SE520251C2 (en) * | 1999-05-20 | 2003-06-17 | Sandvik Ab | Molybdenum silicon type resistance elements for metal powder sintering |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2386072A (en) * | 1944-02-28 | 1945-10-02 | Enos A Stewart | Method of making sponge iron |
GB638114A (en) * | 1946-04-02 | 1950-05-31 | Davide Primavesi | Improvements in or relating to the production of sintered bodies from metal powders |
EP0038558A1 (en) * | 1980-04-21 | 1981-10-28 | Sumitomo Electric Industries Limited | Process for producing sintered ferrous alloys |
EP0066207A1 (en) * | 1981-05-20 | 1982-12-08 | Air Products And Chemicals, Inc. | Process for providing a uniform carbon distribution in ferrous compacts at high temperatures |
JPS5873702A (en) * | 1981-10-28 | 1983-05-04 | Sumitomo Metal Ind Ltd | Production of powder metal forged parts having excellent hardenability and toughness |
-
1991
- 1991-04-29 DE DE4113928A patent/DE4113928A1/en not_active Withdrawn
-
1992
- 1992-02-20 EP EP19920102793 patent/EP0503326A3/en not_active Ceased
- 1992-03-03 US US07/845,033 patent/US5162099A/en not_active Expired - Fee Related
- 1992-03-05 JP JP4048914A patent/JPH0625710A/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2386072A (en) * | 1944-02-28 | 1945-10-02 | Enos A Stewart | Method of making sponge iron |
GB638114A (en) * | 1946-04-02 | 1950-05-31 | Davide Primavesi | Improvements in or relating to the production of sintered bodies from metal powders |
EP0038558A1 (en) * | 1980-04-21 | 1981-10-28 | Sumitomo Electric Industries Limited | Process for producing sintered ferrous alloys |
EP0066207A1 (en) * | 1981-05-20 | 1982-12-08 | Air Products And Chemicals, Inc. | Process for providing a uniform carbon distribution in ferrous compacts at high temperatures |
JPS5873702A (en) * | 1981-10-28 | 1983-05-04 | Sumitomo Metal Ind Ltd | Production of powder metal forged parts having excellent hardenability and toughness |
Non-Patent Citations (2)
Title |
---|
E.KLAR 'METALS HANDBOOK' 1984 , ASM , OHIO 9th edition vol.7 * |
PATENT ABSTRACTS OF JAPAN vol. 7, no. 169 (M-231)(1314) 26. Juli 1983 & JP-A-58 073 702 ( SUMITOMO KINZOKU KOGYO ) 4. Mai 1983 * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1998053939A1 (en) * | 1997-05-27 | 1998-12-03 | Höganäs Ab | Method of monitoring and controlling the composition of sintering atmosphere |
US6303077B1 (en) | 1997-05-27 | 2001-10-16 | Höganäs Ab | Method of monitoring and controlling the composition of sintering atmosphere |
WO1999037425A1 (en) * | 1998-01-21 | 1999-07-29 | Höganäs Ab | Process of preparing an iron-based powder in a gas-tight furnace |
US6355087B1 (en) | 1998-01-21 | 2002-03-12 | Höganäs Ab | Process of preparing an iron-based powder in a gas-tight furnace |
Also Published As
Publication number | Publication date |
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EP0503326A3 (en) | 1993-06-30 |
JPH0625710A (en) | 1994-02-01 |
DE4113928A1 (en) | 1992-09-17 |
US5162099A (en) | 1992-11-10 |
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