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WO1994013418A1 - Composition de poudre a base de fer - Google Patents

Composition de poudre a base de fer Download PDF

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Publication number
WO1994013418A1
WO1994013418A1 PCT/SE1992/000860 SE9200860W WO9413418A1 WO 1994013418 A1 WO1994013418 A1 WO 1994013418A1 SE 9200860 W SE9200860 W SE 9200860W WO 9413418 A1 WO9413418 A1 WO 9413418A1
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WO
WIPO (PCT)
Prior art keywords
weight
powder
iron
less
composition
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.)
Ceased
Application number
PCT/SE1992/000860
Other languages
English (en)
Inventor
Caroline Lindberg
Björn Johansson
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.)
Hoganas AB
Original Assignee
Hoganas 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 Hoganas AB filed Critical Hoganas AB
Priority to PCT/SE1992/000860 priority Critical patent/WO1994013418A1/fr
Publication of WO1994013418A1 publication Critical patent/WO1994013418A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

  • the present invention relates to an iron-based powder which after powder compacting and sintering gives dimen- sionally stable products, i.e. products inherently exhi ⁇ biting similar dimensional changes, also in the event of local density variations.
  • a major advantage of powder-metallurgical processes over conventional techniques is that components of varying complexity can be sintered into final shape immediately after powder compacting, and they therefore require but a relatively limited aftertreatment as compared with e.g. a conventional steel blank. Also in the development of new powder-metallurgical materials, it is an aim to ensure that the dimensional change is small during sintering, since it has been found difficult in practice to maintain the dimensional stability if the dimensional change is considerable. This is especially important in the case of high-strength materials which are difficult to adjust to correct measurement after sintering.
  • the dimensional change is minimal and as inde- pendent as possible of variations in the process para ⁇ meters sintering time, sintering temperature, carbon con ⁇ tent and distribution of alloying substances.
  • the primary objective precisely was to make the dimensional change as independent as possible of these process variables.
  • the alloying substances Ni, Cu and Mo have become uniformly distributed in the material and the contents of these substances can be so selected that variations in the other process para ⁇ meters time, temperature and C-content have but a small effect on the dimensional change.
  • the dimensional change is not constant for different density levels in these materials.
  • the density may in fact vary considerably within the compacted component and in particular if the geometrical shape is complex. This, in turn, may give rise to different dimensional changes locally during sintering, thus making the material "warp", which may mean that it will have to be rejected.
  • the invention is based on the discovery that, during the sintering process, green products made of the powder compositions according to the invention undergo essential ⁇ ly the same dimensional change in spite of density varia- tions within the green products.
  • a density for a density
  • the compact of the powder composition according to the invention is "dimensionally stable" within the density
  • the powder compositions are dimensionally stable also for smaller variations within this range. It should however be noted that the overall dimensional change during the sintering process may vary as in conventional processes, but by using the composition according to the present invention, the pressing tools can be adjusted in size already at the design stage so as to obtain the correct shape after sintering.
  • the powder compositions according to the invention are especially suited for producing products having com ⁇ plex or irregular shape, in which density variations occur during the compacting process.
  • the powders are also suited for producing sintered products in which less or no density variations at all exist within the green product.
  • Another way of expressing the properties of the iron powder according to the invention is that it should satis ⁇ fy the condition
  • ⁇ dL is the variation in the dimensional change (%) within the sintered product measured from the green to the sintered condition
  • Another object of the invention is to produce an iron-powder-based material which after compacting and sin ⁇ tering yields a dimensionally stable product having high strength.
  • the iron- powder-based material according to the invention it is possible with the iron- powder-based material according to the invention to pro ⁇ cute sintered products having a tensile strength above about 450 MPa, especially between 500 and 1000 MPa, and preferably between 550 and 950 MPa, without the sintered product being subjected to subsequent heat treatment.
  • the sintered pro ⁇ ducts according to the invention exhibit a tensile strength exceeding 500 MPa, which is considered a high tensile strength.
  • Yet another object of the invention is to produce a powder which by a simple and inexpensive low-temperature sintering process yields a product having the properties specified above.
  • the invention embraces also such powders as after compacting and sintering exhibit not only good dimen ⁇ sional stability and high strength but also high fatigue strength.
  • the nickel content is compa- ratively high and preferably is in the range of 2-4.5% by weight.
  • these objects can be achieved by a powder composition which, in addition to iron, includes 0.5-4.5% by weight of nickel, 0.65-2.25% by weight of molybdenum, and 0.20-1.0% by weight of car- bon.
  • iron powder compo ⁇ sitions having a C-content between 0.35 and 0.65% are described and, thus, the present invention particularly relates to compositions outside this range.
  • the invention is also directed to products produced from the stated compositions, and to a method for producing the products on the basis of the compositions. Moreover, the invention relates to the use of the powder compositions for produc ⁇ ing sintered products.
  • the other features of the inven- tion are recited in the accompanying claims.
  • compositions containing the components Fe, Ni and Mo in approximately the same contents as in the present invention are previously known from EP 0,334,968. These known compositions are intended for use in the making of products which after sintering and heat treatment (quench ⁇ ing and tempering) are distinguished by a very high strength and high hardness.
  • the EP publication does not contain any information or indication whatever of any particular advantages of these powder compositions when it comes to producing dimensionally stable and high- strength products obtained by simple sintering without any subsequent heat treatment. Since it is well-known that the dimensional accuracy is impaired in heat treatment, it is not possible by using the method disclosed in EP 0,334,968 to achieve the object of the present invention.
  • DOS 2,112,944 also discloses powder compositions including Ni and Mo in such amounts as to place the pre ⁇ sent powder compositions within the ranges here suggested.
  • the compositions of DOS 2,112,944 also include Mn , as a compulsory component, whereas any Mn present in the powder composition according to the invention is an unde ⁇ sirable impurity. Consequently, it is preferred according to the present invention that the content of Mn is at a minimum and less than 0.3% by weight, preferably less than 0.1% by weight.
  • the DOS publication further mentions Ni, Mn, Mo and Fe as completely prealloyed powders.
  • the powder compositions according to the invention have proved well suited for use in so-called low-tempera ⁇ ture sintering, which means sintering at temperatures below about 1150 C.
  • sintering may advantageously be performed in belt furnaces. Sintering in such furnaces usually takes place at temperatures of about 1120°C-1140°C for at most 1 hour, generally between 20 and 40 min.
  • the powder compositions are passed into the sinter- ing furnace, they are first admixed with a lubricant and thereafter moulded in a pressing tool under high pressure.
  • the compacting pressure is in practice about 600 MPa.
  • compositions according to the inven- tion preference is given to such powders in which the nickel content varies between 1.0 and 3.0% by weight and the molybdenum content varies between 0.8 and 2.0% by weight.
  • the best results have hitherto been achieved with compositions in which the content of Ni > the content of Mo, and particularly preferred are .
  • the amount of nickel should be higher, preferably between 2 and 4% by weight.
  • the powder compositions may contain impurities, the content of which should be as low as possible.
  • impurities in the compositions according to the invention are copper, tungsten and phosphorous, which interfere with the dimen ⁇ sional stability.
  • Other impurities that may also have an adverse effect on the sintered product because of oxida- tion are chromium, manganese, silicon and aluminium.
  • the total content of impurities should be maintained below 2% by weight, preferably below 1% by weight.
  • the powder composition of the invention may optionally contain a lubricant of the type which is known to those skilled in the art.
  • Mo is present in solid solution in a water-atomised iron-based powder.
  • This embodiment provides a powder which imparts to the sintered components a more homogeneous structure on micro level as compared with powders in which Mo is not prealloyed to the iron.
  • the sintered density is affected only insignificantly when Mo is pre ⁇ alloyed to the iron. If, on the other hand, Ni is present in solid solution in the iron-based powder, the compress ⁇ ibility of the material is impaired, as is also the sin- tered density (the Example below shows, for instance, how material B in Table 2 will have a very low density after sintering at the compacting pressures used as compared with the other materials.
  • Ni preferably is in metal ⁇ lic form, it being diffusion-alloyed with the iron-based powder prealloyed by means of Mo. Ni may also in this case be mixed with the prealloyed powder.
  • the alloying content ranges are selected under the consideration that the material of the invention should satisfy at least three of the conditions stated above, viz., within the limits specified, provide a dimensionally stable sintered product despite varying density levels within the product, provide an iron-powder-based material which after compacting and sintering yields a dimensional ⁇ ly stable product having high strength, and provide a powder which by simple and inexpensive low-temperature sintering without subsequent heat treatment can yield a product having the properties specified above.
  • FIGS 1-4 show how the dimensional change varies at different density levels during sinter ⁇ ing, and how the tensile strength is affected by the sin- tered density at different contents of alloying substances Ni, Mo and C.
  • These Figures show compacted and sintered powder mixtures where Mo (if present) has been prealloyed in an atomised iron-based powder having a particle size substantially below 200 ⁇ m, while Ni (if present) having a particle size substantially below 15 ⁇ m has thereafter been diffusion-alloyed to the iron-based powder.
  • C in the form of graphite having a particle size substantially below 15 ⁇ m has thereafter been added to the powder.
  • the powder mixtures have then sintered in a belt furnace at 1120-1140 C for 30 min in endothermic atmosphere at a carbon potential corresponding to the carbon content of the material.
  • Fig. la shows how the tensile strength is improved at increasing density and Ni-content
  • Fig. lb shows how the dimensional change is similar at different den ⁇ sity levels for the material of the invention.
  • a too high or a too low Ni-content * i.e., falling outside the stated limits of the inventive material, results in too large variations in dimensional change at different density levels.
  • Fig. 2a illustrates how an increased carbon con ⁇ tent improves the tensile strength
  • Fig. 2b shows that also iron-powder compositions having a carbon con- tent of up to 1% by weight give a low variation in dimen ⁇ sional change at different density levels.
  • Figs 3a and b show that a certain Mo-content is required to meet the requirements as to strength and similar dimensional
  • Fig. 4 shows that also for densities of up to 7.5 g/ 3 cm , the powder composition according to the invention gives small dimensional changes.
  • Composition C according to the invention includes 0.5% carbon. In this context, o it should be mentioned that densities above about
  • 7.3 g/cm 3 to 7.5 g/cm3 can be obtained by subjecting the compacted green porduct to a presintering step at a tem ⁇ perature between 700 and 850°C.
  • the presintered product is then compacted once more before the final sintering 5 step.
  • Example 0 Two different powders (A, B) were prepared by water- atomising an iron melt alloyed both with Mo and with Mo and Ni. The oxygen content was reduced by annealing the atomised powders in reducing atmosphere. In addition, Ni was diffusion-annealed in reducing atmosphere in two con- 5 tents to the iron-based powder which was prealloyed with Mo (C, D). A non-alloyed iron powder was also prepared by water-atomisation and annealed to reduce the oxygen con ⁇ tent. The resulting powder was thereafter diffusion- annealed with different amounts of Mo, Ni and Cu (E, F, 0 G, H). The chemical composition of the different powders appears from Table 1 below. Powder Chemical composition (%)
  • Table 1 Chemical composition of the powder materials tested. The different powders having a particle size sub ⁇ stantially below 200 ⁇ m were admixed with 0.5% graphite having a particle size substantially below 15 ⁇ m and 0.6% Kenolube as lubricant. After mixing, tensile testpieces were compacted at 400, 600 and 800 MPa. Sintering was performed at 1120°C for 30 min in reducing atmosphere

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

Abstract

L'invention concerne une poudre à base de fer permettant de produire par compactage et frittage des composants à haute résistance et sujets à de faibles variations dimensionnelles. Outre du Fe, ladite poudre contient 0,5 à 4,5 % en poids de Ni, 0,65 à 2,25 % en poids de Mo et 0,20 à 1,0 % en poids de C, éventuellement un lubrifiant et des impuretés.
PCT/SE1992/000860 1992-12-11 1992-12-11 Composition de poudre a base de fer Ceased WO1994013418A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/SE1992/000860 WO1994013418A1 (fr) 1992-12-11 1992-12-11 Composition de poudre a base de fer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SE1992/000860 WO1994013418A1 (fr) 1992-12-11 1992-12-11 Composition de poudre a base de fer

Publications (1)

Publication Number Publication Date
WO1994013418A1 true WO1994013418A1 (fr) 1994-06-23

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Family Applications (1)

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PCT/SE1992/000860 Ceased WO1994013418A1 (fr) 1992-12-11 1992-12-11 Composition de poudre a base de fer

Country Status (1)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1561832A1 (fr) * 2004-01-28 2005-08-10 BorgWarner Inc. Procédé de production d'articles durcis par frittage de formes complexes
EP1500449A3 (fr) * 2003-07-22 2006-06-07 Nissan Motor Company, Limited Pignon fritté pour chaîne silencieuse et son procédé de fabrication

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2112944A1 (de) * 1970-03-18 1971-10-07 Birmingham Small Arms Co Ltd Pulvermischung zur Herstellung von Stahlgegenstaenden nach bekannten pulvermetallurgischen Verfahren
EP0200691A1 (fr) * 1985-03-07 1986-11-05 Höganäs AB Poudre mélangée à base de fer pour un alliage fritté
EP0334968A1 (fr) * 1987-09-30 1989-10-04 Kawasaki Steel Corporation Poudre d'acier allie composite et acier allie fritte
DE4031408A1 (de) * 1989-10-03 1991-04-11 Hitachi Powdered Metals Verfahren zur herstellung eines gesinterten maschinenteils
WO1992022395A1 (fr) * 1991-06-12 1992-12-23 Höganäs Ab Composition pulverulente a base de fer, dotee d'une bonne stabilite apres frittage

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2112944A1 (de) * 1970-03-18 1971-10-07 Birmingham Small Arms Co Ltd Pulvermischung zur Herstellung von Stahlgegenstaenden nach bekannten pulvermetallurgischen Verfahren
EP0200691A1 (fr) * 1985-03-07 1986-11-05 Höganäs AB Poudre mélangée à base de fer pour un alliage fritté
EP0334968A1 (fr) * 1987-09-30 1989-10-04 Kawasaki Steel Corporation Poudre d'acier allie composite et acier allie fritte
DE4031408A1 (de) * 1989-10-03 1991-04-11 Hitachi Powdered Metals Verfahren zur herstellung eines gesinterten maschinenteils
WO1992022395A1 (fr) * 1991-06-12 1992-12-23 Höganäs Ab Composition pulverulente a base de fer, dotee d'une bonne stabilite apres frittage

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1500449A3 (fr) * 2003-07-22 2006-06-07 Nissan Motor Company, Limited Pignon fritté pour chaîne silencieuse et son procédé de fabrication
EP1561832A1 (fr) * 2004-01-28 2005-08-10 BorgWarner Inc. Procédé de production d'articles durcis par frittage de formes complexes

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