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WO1990006198A1 - Poudre a base de fer pour la production de pieces frittees - Google Patents

Poudre a base de fer pour la production de pieces frittees Download PDF

Info

Publication number
WO1990006198A1
WO1990006198A1 PCT/SE1989/000712 SE8900712W WO9006198A1 WO 1990006198 A1 WO1990006198 A1 WO 1990006198A1 SE 8900712 W SE8900712 W SE 8900712W WO 9006198 A1 WO9006198 A1 WO 9006198A1
Authority
WO
WIPO (PCT)
Prior art keywords
powder
weight
atomised
iron
amount
Prior art date
Application number
PCT/SE1989/000712
Other languages
English (en)
Inventor
Björn Lindqvist
Patrick Mcgeehan
Original Assignee
Höganäs Ab
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Höganäs Ab filed Critical Höganäs Ab
Publication of WO1990006198A1 publication Critical patent/WO1990006198A1/fr

Links

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%

Definitions

  • the present invention relates to an iron-based powder prealloyed during atomisation and intended for use in the powder metallurgical production of precision-moulded com ⁇ ponents with good dimensional accuracy, hardenability and strength, as well as high density.
  • the alloying components used today for surface har ⁇ dening of powder metallurgical materials mainly comprise Ni, Cu, Mo, C and, to some extent, Cr, Mn and N.
  • the ele ⁇ ments C and/or N are usually added during a heat-treatment operation after sintering.
  • alloying powder There are two common types of alloying powder, namely powder mixtures and so-called atomised powders.
  • the powder mixtures are prepared in that a powder of the alloying substance, either in the form of a metal, or a compound degradable during the sintering process, is ad ⁇ mixed to the iron powder.
  • the so-called atomised steel powders are produced in that a melt of steel containing the desired alloying components is decomposed into powder.
  • One disadvantage of powder mixtures is, however, the risk of segregation which is due to the fact that powders • with different characteristics, e.g. particle size, are intermixed without being mechanically linked to one an- other. This segregation results in a varying composition of the compacts produced from the powder mixture, and therefore also in varying dimensional changes when these compacts are being sintered.
  • Another disadvantage of pow- der mixtures is their tendency to give off dust, especial ⁇ ly when the alloying substance has a very fine particle size. Naturally, this may cause serious environmental pro ⁇ blems.
  • a high compressibility is essential when one wishes to obtain a component of high density; a prerequisite of high strength.
  • the compressibility of a powder mixture is practically identical with that of the constituent iron powder.
  • Ni and Cu to a powder mixture in ⁇ creases the hardenability of the sintered material, but the slow diffusion of, above all, Ni gives the end product a very heterogeneous Ni distribution with areas of soft, residual austenite, because Ni stabilises the austenitic phase.
  • Cu diffuses slightly better than Ni in austenite, and it furthermore melts, which means that a more homoge- neous distribution of Cu than of Ni is obtained in the sintered material.
  • An addition of Cu causes a swelling, and consequently a lower density, of the resulting sin ⁇ tered compact.
  • an atomised powder is needed in which the above-mentioned, heavier alloying components are present in solid solution, i.e. prealloyed in the molten phase.
  • the object of the present invention is to provide an iron-based powder for producing sintered components with good dimensional accuracy, hardenability and strength, as well as high density, said powder having none of the above-mentioned disadvantages of segregation, dusting and low compressibility, due to the solution hardening effect.
  • the present invention has now shown that if the mate ⁇ rial is prealloyed with Mo only, the compressibility is merely slightly affected, compared to when pure Fe powder is used, despite the fact that the alloyed (substitution- dissolved) Mo has a much larger atomic size than Ni, and therefore should produce a higher increase in hardness (Example 1).
  • a minimum amount of 0.5% by weight Mo is re ⁇ quired to obtain a surface hardness sufficient for prac- tical use.
  • 2.5% by weight molybdenum constitutes the upper limit for the amount of Mo which can be prealloyed, if the density requirements concerning the finished component are to be met in pressing with compacting pressures common within powder metallurgical production. Furthermore, a content higher than 2.5% by weight entails a more substan ⁇ tial shrinkage during sintering, and therefore also a poorer dimensional accuracy of the finished components.
  • the upper limit is 2.5% by weight Mo for reasons of com ⁇ pressibility, dimensions, stability and costs. According to the invention, the preferred amount of Mo is 0.75-2% by weight.
  • powder B which has been prealloyed with molybdenum, only has a marginal effect on the compressibility compared to a pure iron powder, in this Example powder A.
  • Powder C which has been prealloyed with Ni, has a much more negative effect on the compressibility, despite the fact that literature as well as known relation ⁇ ships of ultimate strength, hardness and compressibility indicate that the use of nickel should be more favourable if one wishes to avoid a lowering of the compressibility (see Fig. 2).
  • Powder D which is a powder available on the market and intended for the production of hardened compo ⁇ nents, has a considerably poorer compressibility than pow ⁇ der B.
  • Example 2 Example 2
  • Three powders E-G were compacted and hot-forged to full density, the purpose being to examine the hardenabi ⁇ lity of the materials at one and the same density level.
  • the samples produced were cylinders having a diameter of 25 mm and a height of 25 mm.
  • the forged samples were car- burised for 30 min. and at 890°C in endogas with a carbon potential corresponding to a carbon content of 0.8% by weight, whereupon the samples were quenched in oil of 60°C.
  • Powder composition :
  • powder G has a very high surface hardness compared to powders E and F, a character ⁇ istic of a good material for surface hardening operations.
  • Fig. 4 shows the hardening profile of the same mate ⁇ rials as above.
  • powder G not only has a high surface hardness, but also a much greater hardening depth than the powders E and F.
  • a great hardening depth is a property characterising a material suited for sur ⁇ face hardening operations..
  • Fig. 5 illustrates the compressibility in the form of density obtained at a compacting pressure of 410 MPa for an atomised steel powder alloyed with 1.5% by weight molybdenum as a function of the carbon content and the manganese content.
  • the amount of dis ⁇ solved carbon greatly affects the compressibility and should therefore be as low as possible. Furthermore, the manganese content has a negative effect on the compress ⁇ ibility, in particular when exceeding 0.20-0.25% by weight.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)

Abstract

Une poudre à base de fer préalliée pendant l'atomisation contient du Mo dissous afin de produire, dans des conditions normales de compactage et de frittage en production métallurgique de poudre, des pièces moulées avec précision présentant une bonne précision dimensionnelle, une bonne trempabilité et une bonne résistance, ainsi qu'une densité élevée.
PCT/SE1989/000712 1988-12-06 1989-12-06 Poudre a base de fer pour la production de pieces frittees WO1990006198A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8804399-7 1988-12-06
SE8804399 1988-12-06

Publications (1)

Publication Number Publication Date
WO1990006198A1 true WO1990006198A1 (fr) 1990-06-14

Family

ID=20374159

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1989/000712 WO1990006198A1 (fr) 1988-12-06 1989-12-06 Poudre a base de fer pour la production de pieces frittees

Country Status (2)

Country Link
CA (1) CA2004625A1 (fr)
WO (1) WO1990006198A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995008006A1 (fr) * 1993-09-16 1995-03-23 Mannesmann Ag Procede de preparation d'un melange de poudres et son utilisation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB650841A (en) * 1946-05-22 1951-03-07 Davide Primavesi Improvements in or relating to the manufacture of a material with high strength at elevated temperatures by powder metallurgy
US3798022A (en) * 1971-02-17 1974-03-19 Federal Mogul Corp Pre-alloyed nickel-free silicon-free minimal oxide low alloy iron powder

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB650841A (en) * 1946-05-22 1951-03-07 Davide Primavesi Improvements in or relating to the manufacture of a material with high strength at elevated temperatures by powder metallurgy
US3798022A (en) * 1971-02-17 1974-03-19 Federal Mogul Corp Pre-alloyed nickel-free silicon-free minimal oxide low alloy iron powder

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 10, No. 304, M526; & JP,A,61 117 202, (04-06-1986), TOYOTA MOTOR CORP. *
PATENT ABSTRACTS OF JAPAN, Vol. 10, No. 336, M535; & JP,A,61 139 601, (26-06-1986), TOYOTA MOTOR CORP. *
PATENT ABSTRACTS OF JAPAN, Vol. 10, No. 366, C390; & JP,A,61 163 239, (23-07-1986), TOYOTA MOTOR CORP. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995008006A1 (fr) * 1993-09-16 1995-03-23 Mannesmann Ag Procede de preparation d'un melange de poudres et son utilisation

Also Published As

Publication number Publication date
CA2004625A1 (fr) 1990-06-06

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