EP0183017B2 - Sintering process for prealloyed tungsten powder - Google Patents

Sintering process for prealloyed tungsten powder Download PDF

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Publication number
EP0183017B2
EP0183017B2 EP85112578A EP85112578A EP0183017B2 EP 0183017 B2 EP0183017 B2 EP 0183017B2 EP 85112578 A EP85112578 A EP 85112578A EP 85112578 A EP85112578 A EP 85112578A EP 0183017 B2 EP0183017 B2 EP 0183017B2
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Prior art keywords
tungsten
sintering
phase
heat treatment
liquid phase
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German (de)
French (fr)
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EP0183017A1 (en
EP0183017B1 (en
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Rainer Dr. Dipl.-Phys. Schmidberger
Sylvia Dipl.-Ing. Härdtle
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Dornier System GmbH
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Dornier System GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
    • F42B12/00—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material
    • F42B12/02—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the warhead or the intended effect
    • F42B12/04—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the warhead or the intended effect of armour-piercing type
    • F42B12/06—Projectiles, missiles or mines characterised by the warhead, the intended effect, or the material characterised by the warhead or the intended effect of armour-piercing type with hard or heavy core; Kinetic energy penetrators
    • 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
    • B22F3/24—After-treatment of workpieces or articles
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/045—Alloys based on refractory metals

Definitions

  • the invention relates to a sintering process for pre-alloyed tungsten powder according to the preamble of claim 1.
  • Tungsten alloy powders are known from EP98 944, which are already pre-alloyed, whereby the tungsten grains are already covered by the binder phase. Pellets from this powder are compacted by solid phase sintering.
  • the sintered parts are characterized by a polygonal structure of the tungsten phase. The structure is much finer than that of conventional heavy tungsten metals, which were produced from the individual powders (W, Ni, Fe) by mixing, pressing and sintering in the liquid phase.
  • the polygonal structure shows a high consistency of the tungsten phase (contiguity). This means that a multitude of tungsten-tungsten grain boundaries exist that can degrade the mechanical properties of the sintered tungsten heavy metals.
  • the tensile strength and elongation at break deteriorate particularly when interstitial impurities such as oxygen, phosphorus, sulfur and other constituents which are sparingly soluble in tungsten are contained in the alloy. They separate out on the tungsten grain boundaries and cause the grain boundary embrittlement characteristic of pure tungsten.
  • the invention has for its object to provide a sintering process with which a sintered body with a high proportion of tungsten with a fine-grained structure (less than 10 .mu.m of the tungsten phase) has a low contiguity of the tungsten phase.
  • the heat treatment according to the invention in the liquid phase leads to the previously polygonal tungsten grains being rounded off by dissolving in the molten binder phase, without at the same time noticeable grain growth occurring. This results in an approximately spherical shape of the tungsten grains, which reduces the harmful continuity of the tungsten phase, since spheres have less contact area with one another than polygons.
  • Fine grain is required because of the resulting increase in strength (increase in the yield strength according to Hall-Petch relationship a s - 1W where a indicates the average grain size.
  • the duration of the heat treatment with the liquid phase is 2 to 10 minutes. After this time, the tungsten grains are largely rounded. Since the sintered body is already densely sintered when the liquid phase occurs (residual porosity - 1%) and the tungsten phase is relatively uniform, the segregation of tungsten and binder phases that occurs during the usual liquid phase internals will not take place.
  • Solid phase interinterpretation can also be carried out partially in vacuo. If this is not followed by any further sintering under a hydrogen atmosphere, a separate vacuum annealing to remove the hydrogen dissolved in the sintered part can be omitted.
  • the heat treatment with liquid phase can be carried out immediately after the solid phase sintering or only after vacuum annealing.
  • the atmosphere present can be both hydrogen and inert gas. However, the heat treatment can also be carried out in a high vacuum.
  • the cooling rate should not be more than 3 K / min near the solidification temperature.
  • the toughness of the sintered parts is increased by the method according to the invention.
  • the elongation at break increases due to the structural transformation without a significant decrease in strength e.g. from 15% to 40%.
  • the strength and elongation properties of the sintered parts can be changed within wide limits by adjusting the tungsten grain size via the dwell time in the liquid phase during the structural transformation.
  • FIG. 2 shows a workpiece that has been subjected to the treatment according to the invention.
  • Fig. 1 shows the metallographic section of a solid-phase sintered tungsten heavy metal with 90% tungsten.
  • Fig. 1 shows the polygonal structure of the tungsten grains, which creates a considerable contiguity of the tungsten phase.
  • Fig. 2 shows a micrograph of a tungsten heavy metal after heat treatment with liquid phase.
  • the tungsten grains are insignificantly larger than in the solid-phase sintered state. Due to their wrestling, however, the contiguity is significantly lower.
  • An alloyed tungsten heavy metal powder with the composition 90% W, 6% Ni, Co, 2% Fe is compressed with a pressure of 300 N / mm 2 .
  • the compact is sintered in flowing hydrogen at 1 300 ° C for 5 hours and then in a vacuum of 10- 5 mbar at 1050 ° C degassed for 6 hours.
  • the sintered part is then heat-treated in a vacuum at 1,470 ° C. for 5 minutes and then rapidly cooled.
  • the tensile strength of the sample is 1 150 N / mm 2 with an elongation at break of 30%.
  • a tungsten heavy metal powder as in Example 1 is compressed with a pressure of 300 N / mm 2 .
  • the compact is presintered in flowing hydrogen at 900 ° C for 10 hours and then sintered in vacuo at 1,360 ° C for 20 hours.
  • a heat treatment of the sintered part is then carried out in vacuo at 1,470 ° C. for 10 minutes.
  • the tensile strength of the sample is 1 100 N / mm 2 with an elongation at break of 40%.

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  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
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Abstract

This invention relates to a sintering process. More particularly, this invention relates to a process for preparing a sintered form having a tungsten content which comprises the steps of: (a) sintering a porous form of pressed tungsten alloy powders having a high tungsten content in solid phase, and (b) heat treating the sintered part from step (a) in a liquid phase.

Description

Die Erfindung betrifft ein Sinterverfahren für vorlegierte Wolframpulver nach dem Oberbegriff des Anspruchs 1.The invention relates to a sintering process for pre-alloyed tungsten powder according to the preamble of claim 1.

Beim konventionellen Sintern mehrphasiger Wolframlegierungen werden die Metalle pulverförmig gemischt, gepreßt und in der flüssigen Phase gesintert. Bei Wolframlegierungen geschieht dies bei Temperaturen größer als 1 450°C. Innerhalb der flüssigen Phase müssen mindestens drei Prozesse ablaufen:

  • 1. Legierungsbildung
  • 2. Umhüllung der Wolframkörner
  • 3. Verdichten des Presslings
In the conventional sintering of multi-phase tungsten alloys, the metals are mixed in powder form, pressed and sintered in the liquid phase. In the case of tungsten alloys, this occurs at temperatures greater than 1,450 ° C. At least three processes must take place within the liquid phase:
  • 1. Alloy formation
  • 2. Coating the tungsten grains
  • 3. Compact the compact

Die dafür erforderliche lange Verweilzeit in der flüssigen Phase führt zu starkem Kornwachstum, was die Festigkeit verringert.The long residence time required in the liquid phase leads to strong grain growth, which reduces the strength.

Aus der US 39 79 234 ist ein solches Sinterverfahren bekannt, bei dem die Verweilzeit in der flüssigen Phase ca. 1 bis 2 Stunden beträgt, was zum oben genannten starken Kornwachstum führt.Such a sintering process is known from US 39 79 234, in which the residence time in the liquid phase is approximately 1 to 2 hours, which leads to the abovementioned strong grain growth.

Aus der EP98 944 sind Wolframlegierungspulver bekannt, die bereits vorlegiert sind, wobie die Wolframkörner bereits von der Binderphase umhüllt sind. Presslinge aus diesem Pulver werden durch Festphasensintern verdichtet. Die Sinterteile zeichnen sich durch ein polygonales Gefüge der Wolframphase aus. Das Gefüge ist wesentlich feiner als das konventioneller Wälframschwermetalle, die aus den Einzelpulvern (W, Ni, Fe) durch Mischen, Pressen und Sintern in flüssiger Phase hergestellt wurden. Das polygonale Gefüge weist jedoch eine hohe Durchgängigkeit der Wolframphase (Kontiguität) auf. Dies bedeutet, dass eine Vielzahl von Wolfram-Wolfram-Korngrenzen existerit, die die mechanischen Eigenschaften der gesinterten Wolframschwermetalle verschlechtern können. Eine Verschlechterung der Zugfestigkeit und Bruchdehnung ist insbesondere dann vorhanden, wenn interstitielle Verunreinigungen wie Sauerstoff, Phosphor, Schwefel und andere in Wolfram schwerlösliche Bestandteile in der Legierung enthalten sind. Sie scheiden sich auf den Wolfram-Korngrenzen aus und bewirken die für reines Wolfram charakteristische KorngrenzenVersprödung.Tungsten alloy powders are known from EP98 944, which are already pre-alloyed, whereby the tungsten grains are already covered by the binder phase. Pellets from this powder are compacted by solid phase sintering. The sintered parts are characterized by a polygonal structure of the tungsten phase. The structure is much finer than that of conventional heavy tungsten metals, which were produced from the individual powders (W, Ni, Fe) by mixing, pressing and sintering in the liquid phase. The polygonal structure, however, shows a high consistency of the tungsten phase (contiguity). This means that a multitude of tungsten-tungsten grain boundaries exist that can degrade the mechanical properties of the sintered tungsten heavy metals. The tensile strength and elongation at break deteriorate particularly when interstitial impurities such as oxygen, phosphorus, sulfur and other constituents which are sparingly soluble in tungsten are contained in the alloy. They separate out on the tungsten grain boundaries and cause the grain boundary embrittlement characteristic of pure tungsten.

In dem Buch von W. Schatt "Pulvermetallurgie, Sinter- und Verbundwerkstoffe", 1. Auflage 1979, Seiten 423 und 424, ist es bekannt, bereits anlegierte Schwermetallpulver in der flüssigen Phase zu sintern. Die Sintertemperatur ist dabei so zu wählen, daß eine optimale Menge flüssiger Phase auftritt. Maßnahmen zur Vermeidung des Kornwachstums sind nicht offenbart.In the book by W. Schatt "Powder Metallurgy, Sintered and Composite Materials", 1st edition 1979, pages 423 and 424, it is known to sinter already alloyed heavy metal powder in the liquid phase. The sintering temperature should be chosen so that an optimal amount of liquid phase occurs. Measures to avoid grain growth have not been disclosed.

Von R. H. Krock ist in "Proceedings of the 67 annual Meeting of the American Society Testing Materials", June 21 to 26,1964, Seiten 668 bis 679 im Artikel "Sintering and particle growth in tungsten-nickel-iron composites" beschrieben, daß beim Flüssigphasensintern von unter 10 Minuten Dauer bereits "essentially" vollständige Dichte erreichbar ist. Allerdings erfolgt dabei eine Verdreifachung bis Vervierfachung der Korngröße.RH Krock describes in "Proceedings of the 67 annual Meeting of the American Society Testing Materials", June 21 to 26, 1964, pages 668 to 679 in the article "Sintering and particle growth in tungsten-nickel-iron composites" that at Liquid phase sintering of less than 10 minutes in duration "essentially" complete density can be achieved. However, the grain size is tripled to quadrupled.

Der Erfindung liegt die Aufgabe zugrunde, ein Sinterverfahren anzugeben, mit dem ein Sinterkörper mit hohen Wolframanteil mit feinkörnigem Gefüge (kleiner 10 um der Wolframphase) zu schaffen, das eine geringe Kontiguität der Wolframphase aufweist.The invention has for its object to provide a sintering process with which a sintered body with a high proportion of tungsten with a fine-grained structure (less than 10 .mu.m of the tungsten phase) has a low contiguity of the tungsten phase.

Diese Aufgabe wird erfindungsgemäss gelöst mit den in den Ansprüchen angegebenen Verfahrensschritten.This object is achieved according to the invention with the method steps specified in the claims.

Die erfindungsgemässe Wärmebehandlung in der flüssigen Phase führt zu einer Abrundlung der vorher polygonen Wolframkörner durch Anlösung in der schmelzflüssigen Binderphase, ohne dass gleichzeitig nennenswertes Kornwachstum auftritt. Dabei ergibt sich eine annähernd kugelige Gestalt der Wolframkörner, wordurch die schädliche Durchgängigkeit der Wolframphase verringert wird, da Kugeln untereinander weniger Berührungsfläche aufweisen als Polygone.The heat treatment according to the invention in the liquid phase leads to the previously polygonal tungsten grains being rounded off by dissolving in the molten binder phase, without at the same time noticeable grain growth occurring. This results in an approximately spherical shape of the tungsten grains, which reduces the harmful continuity of the tungsten phase, since spheres have less contact area with one another than polygons.

Damit ist die Verbindung der Vorteile des Festphasensinterns und des Flüssigphasensinterns möglich, ohne die Nachteile des sonst üblichen Flüssigsphasensinterns - das Kornwachstum - in Kauf nehmen zu müssen. Feinkörnigkeit ist erforderlich wegen der daraus resultierenden Festigkeitssteigerung (Erhöhung der Streckgrenze nach Hall-PetchBeziehung as - 1W wobei a die mittlere Korngrösse angibt.This makes it possible to combine the advantages of solid phase sintering and liquid phase sintering without having to accept the disadvantages of the otherwise customary liquid phase sintering - grain growth. Fine grain is required because of the resulting increase in strength (increase in the yield strength according to Hall-Petch relationship a s - 1W where a indicates the average grain size.

Kornwachstum tritt bei dem erfindungsgemässen Prozess praktisch nicht auf, da lediglich während sehr kurzer Zeit eine flüssige Phase auftritt. Während der Existenz der Flüssigphase erfolgt lediglich eine Abrundung der W-Körner aufgrund der hohen Grenzflächenspannung des Wolframs in Kontakt mit der flüssigen Binderphase. Legierungsbildung und Verdichtung des porösen Pressgefüges sind bereits bei der Pulverherstellung bzw. während des Festphaseninterns erfolgt.Grain growth practically does not occur in the process according to the invention, since a liquid phase only occurs for a very short time. During the existence of the liquid phase, the W grains are only rounded off due to the high interfacial tension of the tungsten in contact with the liquid binder phase. Alloy formation and compression of the porous press structure have already taken place during the powder production or during the solid phase internal process.

Die Dauer der Wärmebehandlung mit flüssiger Phase beträgt erfindungsgemäß 2 bis 10 min. Nach dieser Zeit sind die Wolframkörner weitgehend abgerundet. Da beim Auftreten der flüssigen Phase der Sinterkörper bereits dicht gesintert ist (Restporosität - 1%) und eine relativ hohe Durchgängigkeit der Wolframphase vorliegt, wird die beim üblichen Flüssigphasenintern auftretende Entmischung von Wolfram- und Binderphase nicht erfolgen.According to the invention, the duration of the heat treatment with the liquid phase is 2 to 10 minutes. After this time, the tungsten grains are largely rounded. Since the sintered body is already densely sintered when the liquid phase occurs (residual porosity - 1%) and the tungsten phase is relatively uniform, the segregation of tungsten and binder phases that occurs during the usual liquid phase internals will not take place.

Die im Vergleich zum Flüssigphasensintern kurze Verweilzeit in flüssiger Phase ist ausreichend, um die gewünschte Gefügeumwandlung zu erzielen. Legierungsbildung und Verdichtung des porösen Teils sind im Gegensatz zum Flüssigphasensintern zum Zeitpunkt der Gefügeumwandlung bereits erfolgt.The short residence time in the liquid phase compared to liquid phase sintering is sufficient to achieve the desired structural transformation. In contrast to liquid phase sintering, the formation of alloys and compression of the porous part have already taken place at the time of structural change.

Während des Festphasensinterns poröser Formteile aus verdichtetem Wolfram-Schwermetallpulver wird zweckmässigerweise mindestens ein Teil der Sinterung unter strömendem Wasserstoff durchgeführt, um den in den legierten Wolframpulvern enthaltenen Restsauerstoff zu entfernen. Dabei ist wichtig, dass im noch offenporigen Zustand des Sinterteils ein weitgehende Entfernung des Sauerstoffs erfolgt. Im Anschluss an die Sinterung unter Wasserstoffatmosphäre sollte eine Vakuumglühung zur Entfernung des im Sinterteil gelösten Wasserstoffs erfolgen. Der gelöste Wasserstoff kann jedoch auch durch Glühung in Schutzgas (z.B. Argon) entfernt werden. Durch die Entfernung des Wasserstoffswerden die mechanische Eigenschaften des Sinterteils verbessert.During the solid phase sintering of porous molded parts made of compressed tungsten heavy metal powder, at least part of the sintering is expediently carried out under flowing hydrogen in order to remove the residual oxygen contained in the alloyed tungsten powders. It is important that the oxygen is largely removed while the sintered part is still open-pore. Following sintering under a hydrogen atmosphere vacuum annealing to remove the hydrogen dissolved in the sintered part. However, the dissolved hydrogen can also be removed by annealing in a protective gas (eg argon). Removing the hydrogen improves the mechanical properties of the sintered part.

Die Festphaseninterung kann auch teilweise im Vakuum durchgeführt werden. Falls sich daran keine weitere Sinterung unter Wasserstoffatmosphäre anschliesst, kann eine gesonderte Vakuumglühung zur Entfernung des im Sinterteil gelösten Wasserstoffs entfallen.Solid phase interinterpretation can also be carried out partially in vacuo. If this is not followed by any further sintering under a hydrogen atmosphere, a separate vacuum annealing to remove the hydrogen dissolved in the sintered part can be omitted.

Die Wärmebehandlung mit flüssiger Phase kann unmittelbar nach des Festphasensinterung oder erst nach erfolgter Vakuumglühung erfolgen. Die dabei vorliegende Atmosphäre kann sowohl Wasserstoff als auch inertgas sein. Die Wärmebehandlung kann jedoch auch im Hochvakuum erfolgen.The heat treatment with liquid phase can be carried out immediately after the solid phase sintering or only after vacuum annealing. The atmosphere present can be both hydrogen and inert gas. However, the heat treatment can also be carried out in a high vacuum.

Wichtig ist, dass die Zeit, während der die flüssige Phase vorliegt, genau kontrolliert wird. Zu langes Verweilen in flüssiger Phase führt zu unerwünschtem Kornwachstum und muss daher vermieden werden. Es ist also erforderlich, Aufheizung und Abkühlung im Bereich der Flüssigphase möglichst rasch durchzuführen.It is important that the time during which the liquid phase is present is carefully controlled. Spending too long in the liquid phase leads to undesirable grain growth and must therefore be avoided. It is therefore necessary to heat and cool the liquid phase as quickly as possible.

Falls die Wärmebehandlung in H2-Atmosphäre durchgeführt wird, muss bei der Abkühlung eine Ausscheidung des gelösten Wasserstoffs im Bereich der Erstarrungstemperatur vermieden werden, da sie zu Porenbildung führen kann. Zu diesem Zweck sollte die Abkühlgeschwindigkeit in der Nähe der Erstarrungstemperatur nicht mehr als 3 K/min betragen.If the heat treatment is carried out in an H 2 atmosphere, the elimination of the dissolved hydrogen in the area of the solidification temperature must be avoided during cooling, since this can lead to pore formation. For this purpose, the cooling rate should not be more than 3 K / min near the solidification temperature.

Nach Durchlaufen des Erstarrungsbereichs führt eine weitere rasche Abkühlung (ca. 100 K/min) auf Temperaturen unterhalb von ca. 800°C ebenfalls zu einer weiteren Verbesserung der mechanischen Eigenschaften. Der Grund dafür ist vermutlich die Verhinderung von Korngrenzensegregation durch störende Verunreinigungen.After passing through the solidification area, further rapid cooling (approx. 100 K / min) to temperatures below approx. 800 ° C also leads to a further improvement in the mechanical properties. The reason for this is probably the prevention of grain boundary segregation by interfering contaminants.

Unterhalb von 800°C verläuft der Segregationsprozess so langsam, dass eine normale Ofenabkühlung (ca. 20 K/min) ausreicht, um eine Verschlechterung der mechanischen Eigenschaften zu verhindern.Below 800 ° C, the segregation process is so slow that normal furnace cooling (approx. 20 K / min) is sufficient to prevent the mechanical properties from deteriorating.

Durch das erfindungsgemässe Verfahren wird die Zähigkeit der Sinterteile erhöhlt. Die Bruchdehnung steigt durch die Gefügeumwandlung ohne wesentliche Abnahme der Festigkeit z.B. von 15% auf 40%.The toughness of the sintered parts is increased by the method according to the invention. The elongation at break increases due to the structural transformation without a significant decrease in strength e.g. from 15% to 40%.

Festigkeits- und Dehnungseigenschaften der gesinterten Teile lassen sich in weiten Grenzen durch die Einstellung der Wolfram-Korngrösse über die Verweilzeit in flüssiger Phase bei der Gefügeumwandlung verändern.The strength and elongation properties of the sintered parts can be changed within wide limits by adjusting the tungsten grain size via the dwell time in the liquid phase during the structural transformation.

Steigende Korngrösse durch länger andauernde Wärmebehandlung in flüssiger Phase führt zu abnehmender Festigkeit bei steigender Bruchdehnung.Increasing grain size due to longer-lasting heat treatment in the liquid phase leads to decreasing strength with increasing elongation at break.

Die Wirkung des erfindungsgemässen Verfahrens wird anhand zweier Schliffbilder gezeigt.The effect of the method according to the invention is shown using two micrographs.

Fig. 1 zeigt ein festphasengesintertes Werkstück,1 shows a solid phase sintered workpiece,

Fig. 2 zeigt ein Werkstück, das der erfindungsgemässen Behandlung unterzogen wurde.2 shows a workpiece that has been subjected to the treatment according to the invention.

Fig. 1 zeigt den metallographischen Schliff eines festphasengesinterten Wolfram-Schwermetells mit 90% Wolframanteil. Man erkennt die polygonale Struktur der Wolframkörner, die eine erhebliche Kontiguität der Wolframphase erzeugt.Fig. 1 shows the metallographic section of a solid-phase sintered tungsten heavy metal with 90% tungsten. One can see the polygonal structure of the tungsten grains, which creates a considerable contiguity of the tungsten phase.

Fig. 2 zeigt ein Schliffbild eines Wolfram-Schwermetalls nach Durchführung einer Wärmebehandlung mit flüssiger Phase. Die Wolframkörner sind unwesentlich grösser als im festphasengesinterten Zustand. Durch ihre Abrungung ergibt sich jedoch eine deutlich geringere Kontiguität.Fig. 2 shows a micrograph of a tungsten heavy metal after heat treatment with liquid phase. The tungsten grains are insignificantly larger than in the solid-phase sintered state. Due to their wrestling, however, the contiguity is significantly lower.

Beispiel 1example 1

Ein legiertes Wolframschwermetallpulver der Zusammensetzung 90% W, 6% Ni, Co, 2% Fe wird mit einem Druck von 300 N/mm2 verdichtet. Der Pressling wird in strömendem Wasserstoff bei 1 300°C 5 Stunden lang gesintert und danach im Vakuum von 10-5 mbar bei 1 050°C 6 Stunden lang entgast. Anschliessend wird das gesinterte Teil im Vakuum bei 1 470°C 5 Minuten wärmebehandelt und danach rasch abgekühlt. Die Zugfestigkeit der Probe beträgt 1 150 N/mm2 bei einer Bruchdehnung von 30%.An alloyed tungsten heavy metal powder with the composition 90% W, 6% Ni, Co, 2% Fe is compressed with a pressure of 300 N / mm 2 . The compact is sintered in flowing hydrogen at 1 300 ° C for 5 hours and then in a vacuum of 10- 5 mbar at 1050 ° C degassed for 6 hours. The sintered part is then heat-treated in a vacuum at 1,470 ° C. for 5 minutes and then rapidly cooled. The tensile strength of the sample is 1 150 N / mm 2 with an elongation at break of 30%.

Beispiel 2Example 2

Ein Wolframschwermetallpulver wie in Beispiel 1 wird mit einem Druck von 300 N/mm2 verdichtet. Der Pressling wird in strömendem Wasserstoff bei 900°C 10 Stunden lang vorgesintert und danach im Vakuum bei 1 360°C 20 Stunden lang fertiggesintert. Anschliessend wird eine Wärmebehandlung des gesinterten Teils im Vakuum bei 1 470°C 10 min durchgeführt. Die Zugfestigkeit der Probe beträgt 1 100 N/mm2 bei einer Bruchdehnung von 40%.A tungsten heavy metal powder as in Example 1 is compressed with a pressure of 300 N / mm 2 . The compact is presintered in flowing hydrogen at 900 ° C for 10 hours and then sintered in vacuo at 1,360 ° C for 20 hours. A heat treatment of the sintered part is then carried out in vacuo at 1,470 ° C. for 10 minutes. The tensile strength of the sample is 1 100 N / mm 2 with an elongation at break of 40%.

Claims (5)

1. Sintering process for prealloyed tungsten powder the grains of which are already enveloped in a binder phase, in which process a porous moulded part of compressed powder is sintered in the solid phase, characterised in that sintering is followed by a short heat treatment for 2 to 20 minutes with liquid phase, which treatment is continued until all the tungsten grains have been rounded off and a fine grained structure with less than 10 um of the tungsten phase is obtained and in that the heat treatment with the liquid phase is begun when the compressed material has been compacted to a porosity of less than 1 % by the preceding solid phase sintering.
2. Process according to claim 1, characterised in that sintering is carried out in a stream of hydrogen and the heat treatment is carried out in a high vacuum of ≤10-5 mbar.
3. Process according to one of the preceding claims, characterised in that degasification is carried out before the heat treatment by maintaining the temperature at the sintering temperature in a high vacuum at a pressure below 10-5 mbar.
4. Process according to one of the preceding claims, characterised in that cooling is carried out at the end at about 100 kmin.
5. Process according to one of the preceding claims, characterised in that an alloy of 90 to 97% W, remainder Ni:Fe:Co in ratios by weight of 3:1:1, is sintered for 5 hours in a stream of hydrogen at 1,300°C, degasified in a high vacuum of ≤10-5 mbar at 1,300°C for 0.5 hours, subjected to a heat treatment at 1,470°C in a high vacuum for 5 minutes and finally cooled to room temperature.
EP85112578A 1984-10-20 1985-10-04 Sintering process for prealloyed tungsten powder Expired - Lifetime EP0183017B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85112578T ATE36481T1 (en) 1984-10-20 1985-10-04 SINTERING PROCESS FOR PRE-ALLOYED TUNGSTEN POWDER.

Applications Claiming Priority (2)

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DE3438547A DE3438547C2 (en) 1984-10-20 1984-10-20 Heat treatment process for pre-alloyed, two-phase tungsten powder
DE3438547 1985-10-20

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EP0183017A1 EP0183017A1 (en) 1986-06-04
EP0183017B1 EP0183017B1 (en) 1988-08-17
EP0183017B2 true EP0183017B2 (en) 1991-01-09

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US (1) US4698096A (en)
EP (1) EP0183017B2 (en)
JP (1) JPS61104002A (en)
AT (1) ATE36481T1 (en)
DE (2) DE3438547C2 (en)

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NL8403031A (en) * 1984-10-05 1986-05-01 Philips Nv METHOD FOR MANUFACTURING A SCANDAL FOLLOW-UP CATHOD AND SCANDAL FOLLOW-UP CATHOD Manufactured By This Method
JP2531623B2 (en) * 1986-02-12 1996-09-04 三菱マテリアル株式会社 Manufacturing method of W-based sintered alloy flying body having high toughness
JP2552264B2 (en) * 1986-02-12 1996-11-06 三菱マテリアル株式会社 Method for producing W-based alloy sintered body having high toughness
FR2617192B1 (en) * 1987-06-23 1989-10-20 Cime Bocuze PROCESS FOR REDUCING THE DISPERSION OF THE VALUES OF THE MECHANICAL CHARACTERISTICS OF TUNGSTENE-NICKEL-IRON ALLOYS
US4762559A (en) * 1987-07-30 1988-08-09 Teledyne Industries, Incorporated High density tungsten-nickel-iron-cobalt alloys having improved hardness and method for making same
US4744944A (en) * 1987-08-05 1988-05-17 Gte Products Corporation Process for producing tungsten heavy alloy billets
US5008071A (en) * 1988-01-04 1991-04-16 Gte Products Corporation Method for producing improved tungsten nickel iron alloys
US4793969A (en) * 1988-01-14 1988-12-27 Gte Products Corporation Process for producing tungsten heavy alloy sheet using high temperature processing techniques
US4777015A (en) * 1988-01-14 1988-10-11 Gte Products Corporation Process for producing tungsten heavy alloy sheet using a metallic salt binder system
US4800064A (en) * 1988-01-14 1989-01-24 Gte Products Corporation Process for producing tungsten heavy alloy sheet using hydrometallurgically produced tungsten heavy alloy
FR2633205B1 (en) * 1988-06-22 1992-04-30 Cime Bocuze PROCESS FOR DIRECT SHAPING AND OPTIMIZATION OF THE MECHANICAL CHARACTERISTICS OF HIGH-DENSITY TUNGSTEN ALLOY PERFORMING PROJECTILES
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DE4113177C2 (en) * 1991-04-23 1993-10-21 Nwm De Kruithoorn Bv Process for making a penetrator
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JP3052240B2 (en) * 1998-02-27 2000-06-12 東京タングステン株式会社 Rotating anode for X-ray tube and method for producing the same
FR2830022B1 (en) * 2001-09-26 2004-08-27 Cime Bocuze HIGH POWER SINTERED TUNGSTEN BASE ALLOY
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Also Published As

Publication number Publication date
ATE36481T1 (en) 1988-09-15
EP0183017A1 (en) 1986-06-04
DE3438547A1 (en) 1986-04-30
DE3438547C2 (en) 1986-10-02
JPS61104002A (en) 1986-05-22
US4698096A (en) 1987-10-06
DE3564391D1 (en) 1988-09-22
EP0183017B1 (en) 1988-08-17

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