EP0354389B1 - Procédé pour la fabrication de pièces d'acier fritté et pièces ainsi obtenues - Google Patents

Procédé pour la fabrication de pièces d'acier fritté et pièces ainsi obtenues Download PDF

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Publication number
EP0354389B1
EP0354389B1 EP89113211A EP89113211A EP0354389B1 EP 0354389 B1 EP0354389 B1 EP 0354389B1 EP 89113211 A EP89113211 A EP 89113211A EP 89113211 A EP89113211 A EP 89113211A EP 0354389 B1 EP0354389 B1 EP 0354389B1
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EP
European Patent Office
Prior art keywords
sintered
process according
filler
minutes
temperature
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.)
Expired - Lifetime
Application number
EP89113211A
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German (de)
English (en)
Other versions
EP0354389A1 (fr
Inventor
Dieter Dr.Rer.Nat. Pohl
Hans A. Dipl.-Ing. Härle
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schwaebische Huettenwerke Automotive GmbH
Original Assignee
Schwaebische Huettenwerke Automotive GmbH
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Application filed by Schwaebische Huettenwerke Automotive GmbH filed Critical Schwaebische Huettenwerke Automotive GmbH
Publication of EP0354389A1 publication Critical patent/EP0354389A1/fr
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Classifications

    • 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
    • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
    • 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
    • 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
    • B22F3/26—Impregnating
    • 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

Definitions

  • the invention relates to a method for producing a molded part from sintered steel, sintered steel powder being compression-molded and sintered, after which the sintered part is austenitized by heating to temperatures above 800 ° C. and then rapidly cooled.
  • the invention also relates to a molded part produced by the method.
  • US Pat. No. 2,566,752 describes a method for producing an iron-containing metal part, namely a composite part.
  • the composite part including copper infiltrated to achieve a higher strength For this purpose, it is proposed, after cooling, for example in oil or water, to reheat the metal to a temperature between 300 and 600 ° C. for a period of one to three hours in order to achieve infiltration of the desired constituents into the structure and thereby to increase the strength of the part.
  • One of the essential features of the known molded parts made of sintered steel is the accuracy with which they can be produced. Diameter tolerances of high quality can be achieved. After the usual work sequence with a compression molding and a subsequent sintering, the sintered molding is calibrated for this. The high accuracy is achieved through the calibration process. Shaped parts that are not post-treated by calibration or another work process do not have such a high tolerance with sufficient repeatability.
  • Sintered steels can achieve considerable yield strengths and tensile strength values, but their plastic deformability, which is measured, for example, as the elongation at break, and their toughness, which is measured, for example, as impact energy, are low.
  • the strength limits the achievable accuracy of sintered molded parts. This is because post-sintering is economical, e.g. by calibration, can only be carried out if the strength of the material does not exceed 500 to a maximum of 600 N / mm2. Sintered steels with a significantly higher tensile strength can be easily produced, e.g. up to about 1200 N / mm2 tensile strength, because molded parts made from such materials can also be pressed and sintered, but they can no longer be economically calibrated to increase accuracy.
  • a high strength of sintered steels can be achieved by alloying measures or by heat treatment, if necessary by a combination of both measures. Alloy-related measures have the disadvantage mentioned that they have high strength is achieved, but no economic calibration was possible to achieve the required accuracy.
  • the present invention is therefore based on the object of providing a method for producing a sintered part and a sintered part produced thereafter, which has a high strength but at the same time also has good ductility, with the aim of achieving the highest possible dimensional accuracy.
  • the temperature range and the conversion time depend on the steel composition.
  • the first possibility is that the compression of the part to be sintered is chosen so high that a pore volume of less than 8% is achieved. With such a percentage, the pores are essentially no longer interconnected. This means that salt can then only settle into pores during the heat treatment which are open towards the surface of the sintered part. From there it can be easily washed out later.
  • the second possibility is that the pores of the sintered part are at least partially filled with a filler which is resistant to the agents and chemicals used in a rapid cooling in a bath.
  • metallic substances whose melting point is above the temperature of austenitizing but below the sintering temperature. This is e.g. generally the case for copper and corresponding copper alloys.
  • non-metallic substances such as e.g. ceramic materials are used.
  • ceramic materials e.g. Silicates or a mixture or a thin paste of talc and water glass possible.
  • Numerous sintered steel powders commonly used in sintering molded parts are suitable for intermediate stage tempering. Both fully alloyed, i.e. atomize, as well as mixed alloy or alloyed powder. Pre-alloyed powders are obtained by melting iron with the desired alloy components, after which the melt is atomized into powder, which is then compression-molded in the usual way.
  • Mixed alloy powder means that iron powder is mixed with alloy powder, after which the dry powder mixture is also compression molded.
  • a middle way is the combination of both processes, which creates an alloyed powder for the subsequent compression molding.
  • alloyed powders with, for example, 1.5 to 2% by weight of Ni, 0.3 to 0.6% by weight of Mo will be mixed with a corresponding residual amount of iron, and 0.3 to 1% by weight of graphite can also be added .
  • copper can be tolerated as a shrinking alloy element in the usual framework.
  • a molded part 1 is formed whose pores 2 are filled with copper.
  • Tests with tensile tests have shown the following property values for the above example: Status R p N / mm2 R m N / mm2 A% State of the art only sintered 420..510 530..680 2.0..3.0 State of the art: hardened and tempered 900..1040 1050..1165 1.6..2.9 bainitized (intermediate stage tempered) 685..740 780..850 7.5.9.3
  • field 3 with an alloy of FE-Cu-Ni-Mo-C having the highest tensile strength values with a relatively low elongation. If the same sintered alloy steel is hardened and tempered, field 4 is obtained. When copper is infiltrated at the same time during the sintering process and subsequent heat treatment as in field 4, field 5 with the highest tensile strength values is obtained, although the elongation is again relatively low.
  • Field 6 shows the values for a sintered part produced by the method according to the invention. As can be seen from this, the tensile strength is significantly higher than that of sintered steels without any treatment and only insignificantly lower than with a hardened and tempered alloy steel. In contrast, however, the percentage elongation is several times better.

Claims (20)

  1. Procédé de fabrication d'une pièce moulée en acier à fritter, dans lequel de la poudre d'acier à fritter est pressée dans un moule et frittée, cette pièce frittée étant ensuite austénitisée par chauffage à des températures supérieures à 800°C puis refroidie rapidement, caractérisé en ce que le pressage de la pièce à fritter est suffisamment fort pour qu'un volume de pores inférieur à 8% soit atteint et en ce que, après le traitement thermique austénitique, la pièce frittée est refroidie à une température de 280 à 450°C et maintenue dans cette gamme de température entre 5 et 60 minutes, ce qui produit une microstructure bainitique de sa structure.
  2. Procédé de fabrication d'une pièce moulée en acier à fritter, dans lequel de la poudre d'acier à fritter est pressée dans un moule et frittée, cette pièce frittée étant ensuite austénitisée par chauffage à des températures supérieures à 800°C puis refroidie rapidement, caractérisé en ce que les pores de la pièce frittée sont remplis au moins partiellement d'une matière de remplissage qui est résistante aux agents et produits chimiques utilisés dans un bain lors du refroidissement rapide et en ce que, après le traitement thermique austénitique, la pièce frittée est refroidie à une température de 280 à 450°C et maintenue dans cette gamme de température entre 5 et 60 minutes, ce qui produit une microstructure bainitique de sa structure.
  3. Procédé selon la revendication 1 ou 2, caractérisé en ce que le refroidissement se fait jusqu'à une gamme de température de 320 à 360°C.
  4. Procédé selon la revendication 1, 2 ou 3, caractérisé en ce que la pièce frittée est maintenue entre 20 et 40 minutes dans ladite gamme de température.
  5. Procédé selon l'une des revendications 1 à 4, caractérisé en ce que le traitement thermique austénitique est effectué entre 800 et 900°C pendant une durée de 10 à 60 minutes.
  6. Procédé selon la revendication 5, caractérisé en ce que le traitement thermique austénitique est effectué entre 800 et 900°C pendant une durée de 15 à 20 minutes.
  7. Procédé selon la revendication 1, caractérisé en ce que la pièce à fritter subit un premier pressage, puis un premier frittage et ensuite un second pressage et un frittage final.
  8. Procédé selon la revendication 2, caractérisé en ce qu'on utilise comme matière de remplissage une matière métallique dont le point de fusion se trouve au-dessus de la température d'austénitisation, mais au-dessous de la température de frittage.
  9. Procédé selon la revendication 8, caractérisé en ce que l'on utilise comme matière de remplissage du cuivre ou un alliage de cuivre.
  10. Procédé selon la revendication 2, caractérisé en ce qu'on utilise comme matière de remplissage une matière céramique.
  11. Procédé selon la revendication 10, caractérisé en ce qu'on utilise comme matière de remplissage un silicate tel que le talc et/ou du verre soluble.
  12. Procédé selon l'une des revendications 1 à 11, caractérisé en ce que l'on utilise comme matière à fritter une poudre d'alliage contenant, à part le fer, de 1,5 à 2% en poids de Ni et de 0,3 à 0,6% en poids de Mo, à laquelle est mélangé de 0,3 à 1,0% en poids de graphite.
  13. Pièce moulée en acier fritté, caractérisée en ce qu'elle présente un volume des pores inférieur à 8% et en ce que sa microstructure est en bainite.
  14. Pièce moulée en acier fritté selon la revendication 13, caractérisée en ce que les pores de la pièce frittée sont remplis au moins partiellement d'une matière de remplissage qui est résistante aux agents et produits chimiques utilisés dans un bain lors d'un refroidissement rapide et en ce que sa microstructure est en bainite.
  15. Pièce moulée selon la revendication 14, caractérisée en ce que ses pores sont remplis au moins partiellement d'un métal non ferreux dont le point de fusion est compris entre 920 et 1230°C.
  16. Pièce moulée selon la revendication 15, caractérisée en ce que le métal non ferreux est le cuivre ou un alliage de cuivre.
  17. Pièce moulée selon la revendication 14, caractérisée en ce que ses pores sont remplis au moins partiellement d'une matière non métallique.
  18. Pièce moulée selon la revendication 17, caractérisée en ce que la matière non métallique est une matière céramique telle qu'un silicate, du talc et/ou du verre soluble.
  19. Pièce moulée selon la revendication 13 ou 14, caractérisée en ce que son poids spécifique est compris entre 6,8 g/cm³ et 7,4 g/cm³.
  20. Pièce moulée selon la revendication 19, caractérisée en ce que son poids spécifique vaut environ 7,3 g/cm³.
EP89113211A 1988-07-27 1989-07-19 Procédé pour la fabrication de pièces d'acier fritté et pièces ainsi obtenues Expired - Lifetime EP0354389B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3825463 1988-07-27
DE3825463A DE3825463A1 (de) 1988-07-27 1988-07-27 Verfahren zum herstellen eines formteiles aus sintermetall und daraus hergestelltes formteil

Publications (2)

Publication Number Publication Date
EP0354389A1 EP0354389A1 (fr) 1990-02-14
EP0354389B1 true EP0354389B1 (fr) 1994-05-04

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Application Number Title Priority Date Filing Date
EP89113211A Expired - Lifetime EP0354389B1 (fr) 1988-07-27 1989-07-19 Procédé pour la fabrication de pièces d'acier fritté et pièces ainsi obtenues

Country Status (4)

Country Link
EP (1) EP0354389B1 (fr)
DE (2) DE3825463A1 (fr)
ES (1) ES2054943T3 (fr)
PT (1) PT91283B (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19521941C1 (de) * 1995-06-07 1996-10-02 Mannesmann Ag Verfahren und Vorrichtung zur Herstellung von Sinterteilen
DE19524251C1 (de) * 1995-07-04 1997-02-13 Supervis Ets Verfahren zur Herstellung eines gesinterten Formteiles
JP4001450B2 (ja) * 2000-05-02 2007-10-31 日立粉末冶金株式会社 内燃機関用バルブシートおよびその製造方法
SE0201824D0 (sv) * 2002-06-14 2002-06-14 Hoeganaes Ab Pre-alloyed iron based powder

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2566752A (en) * 1948-10-14 1951-09-04 American Electro Metal Corp Method of producing a ferrous metal article infiltrated with a cuprous infiltrant
US4002471A (en) * 1973-09-24 1977-01-11 Federal-Mogul Corporation Method of making a through-hardened scale-free forged powdered metal article without heat treatment after forging
JPS50115108A (fr) * 1974-02-21 1975-09-09
US4343661A (en) * 1978-11-15 1982-08-10 Caterpillar Tractor Co. Method of making a low temperature bainite steel alloy gear
DE3142359A1 (de) * 1981-10-26 1983-05-05 Horst Dipl.-Phys. Dr. 6000 Frankfurt Mühlberger Verfahren und vorrichtung zur waermebehandlung von werkstuecken

Also Published As

Publication number Publication date
DE3825463A1 (de) 1990-02-01
PT91283B (pt) 1995-03-01
ES2054943T3 (es) 1994-08-16
EP0354389A1 (fr) 1990-02-14
PT91283A (pt) 1990-02-08
DE58907598D1 (de) 1994-06-09

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