EP0011981B1 - Pulvermetallurgisches Verfahren zur Herstellung von Formkörpern - Google Patents

Pulvermetallurgisches Verfahren zur Herstellung von Formkörpern Download PDF

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Publication number
EP0011981B1
EP0011981B1 EP79302649A EP79302649A EP0011981B1 EP 0011981 B1 EP0011981 B1 EP 0011981B1 EP 79302649 A EP79302649 A EP 79302649A EP 79302649 A EP79302649 A EP 79302649A EP 0011981 B1 EP0011981 B1 EP 0011981B1
Authority
EP
European Patent Office
Prior art keywords
powder
tin
metal
low melting
melting point
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
Application number
EP79302649A
Other languages
English (en)
French (fr)
Other versions
EP0011981A1 (de
Inventor
Sydney Morton Kaufman
Sang-Kee Suh
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.)
Ford Werke GmbH
Ford France SA
Ford Motor Co Ltd
Original Assignee
Ford Werke GmbH
Ford France SA
Ford Motor Co Ltd
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 Ford Werke GmbH, Ford France SA, Ford Motor Co Ltd filed Critical Ford Werke GmbH
Publication of EP0011981A1 publication Critical patent/EP0011981A1/de
Application granted granted Critical
Publication of EP0011981B1 publication Critical patent/EP0011981B1/de
Expired 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
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/17—Metallic particles coated with metal
    • 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
    • C22C33/0207—Using a mixture of prealloyed powders or a master alloy

Definitions

  • This invention relates to a method of making powder compacts.
  • Powdered metal compacts have been used in some industrial applications, but have not generally found full acceptance because the extra method steps and the added cost required to obtain a reasonable strength level and density in the powdered metal compact have been excessive, particularly when compared to similar parts obtained by melt formation.
  • the conventional commercial mode of processing powdered metal to form compacts typically comprises (a) blending and milling together selected powder elements in the presence of a lubricant, (b) compacting the .nechanically blended charge (c) heating the compact under a reducing atmosphere for a period of 30 min. at 810°C to volatilize the lubricant, and (d) sintering the compact at an appropriate temperature.
  • This has resulted at best in a green density prior to sintering of about 79-86% and a sintered density of 80-89% of theoretical.
  • a higher density level would require additional hot forging to increase the strength level and reduce porosity.
  • the coating in the latter Patent Specification amounts to between 12% and 30% by weight of the metallic object.
  • the latter proposal also suggests a pressure of between 540 and 772 MPa (35 and 50 tsi).
  • U.S. Patent Specification No. 1,986,197 there is described a process in which the metal powder compressed is electro-plated with a low melting point metal.
  • the latter Patent also provides for high pressures.
  • the present invention seeks to provide a method of producing a metal powder compact which is less expensive to implement and causes less wear on the tools involved in the manufacture.
  • a method of producing a metal powder compact which comprises compacting iron powder in the presence of a low melting point metal at a temperature sufficient to melt the low melting point metal, characterised in that the iron powder is compacted in the presence of from 1% to 5% by weight of the low melting point metal, that the iron powder is compacted at a pressure no greater than 463 MPa (30 tsi) and that the iron powder particles are coated with the low melting point metal by dry impact coating.
  • the dry impact coating is effected by ball milling and milling elements composed of or carrying the low melting point metal.
  • 2-4% of a low melting metal ingredient (preferably selected from tin, a copper-tin alloy, a copper-lead alloy and lead) is added to a coarse or fine iron powder and the mixture is subsequently warm-briquetted (preferably at a temperature of 230 to 345°C (450-650°F)) to form a liquid phase of said addition agent while consolidating the powder.
  • the particle size of the base iron powder is preferably relatively fine (4-5 microns) and about 2.5% of a liquid phase promoting ingredient, particularly tin, is preferably added thereto, the blended mixture being warm briquetted at a temperature of 230 to 345°C (450 to 650°F).
  • the compact may then be sintered.
  • a cryogenically- produced fine powder is used as the source of the powdered metal.
  • the present invention includes two preferred embodiments:- (1) the addition of 1-5% of a low-melting metal, such as tin, to an iron powder which results, after warm briquetting, in a compact having 25% less porosity and increased strength compared with a conventional cold briquetted compact; and (II) the addition of 1-5% of a low melting metal, such as tin or lead, to a fine particle size iron powder, which results, after warm briquetting and sintering, in a product having only 3% porosity compared with 20% porosity when tin or lead is not used.
  • a low-melting metal such as tin
  • a low melting metal such as tin or lead
  • a preferred method for carrying out the first aspect of this invention is as follows:
  • This step is to transfer, by impact, a portion of the tin ingredient, carried by the ball milling elements, to form a tin shell about substantially each particle of the powder.
  • the coating is generated by abrasion or scratching of the powder particle against the surface of the ball milling elements. This obviously is accomplished by rotating the housing of the ball mill machine to impart a predetermined abrading force from the balls.
  • the ball milling operation will cold work or generate defect sites in substantially all of the powder particles above 124 microns; since the majority of the particles selected for the process will be below said size range, they will generally be free of cold work or defect sites.
  • the ball milling operation should be carried sufficiently long so that substantially each particle will be fully coated; this requires statistically a minimum period of time so that tin coating will preferably be continuous.
  • the particles will be in a condition where they will all substantially have a continuous tin envelope (coating or shell).
  • the shell should preferably be an impervious continuous envelope about each particle, it is not critical that it be absolutely impervious.
  • the warm briquetting temperature could be raised to as much as 732°C (1350°F) if necessitated by the requirement to melt the metal coating, or to improve densification by plastic deformation.
  • the pressure applied should be no more than 463 MPa (30 tsi), and preferably in the range of 154-463 MPa (10-30 tsi), so that wear on the tooling used for agglomeration is reduced to a minimum.
  • Agglomeration or compaction may be carried out by a conventional press to obtain the maximum desired densities herein. Compact densities herein are considerably improved to 80% or more of theoretical. density.
  • the presence of the solid tin or low melting envelope about the particles improves compressibility acting as a lubricant, and the liquified metal phase acts as a pore filler during the compaction operation.
  • a density of about 82% of theoretical or 6.4 g. per cubic centimeter is typically obtained using a compressive force of about 463 MPa (30 tsi); with a dry impact coated powder herein; densities of about 7.0 g. per cubic centimeter can be obtained at the same force level.
  • the first method is varied in either or both of two respects.
  • the iron powder selected is limited to a fine particle size, averaging 4-5 microns. This can preferably be obtained by extracting the iron powder as a byproduct of processing of scrap or machining chips from industrial metal work.
  • scrap metal in the form of machine turnings are segregated or selected.
  • Machine turnings are segments of ribbons of low carbon or alloy steel; the turnings should be selected to have a surface to volume ratio of at least 60:1.
  • the machine turnings may be shavings cut from alloy bar, and the bar may have a chemistry which includes alloying ingredients such as manganese, silicon, chromium, nickel and molybdenum.
  • the turnings will have a size characterized by a width of .254-2.54 cm (.1-1.0"), thickness of .0127-.0762 cm (.005-.03”), and a length of 2.54-254 cm (1-100").
  • Machine turnings are usually not suitable for melting in an electric furnace because they prevent efficient melt down due to such surface to volume ratio.
  • the turnings should be selected to be generally compatible in chemistry when in the final product; this is achieved optimally when the turnings are selected from a common machining operation where the same metal stock was utilized in forming all the turnings.
  • the selected scrap pieces are put into a suitable charging passage leading to a ball milling machine (or equivalent impacting device).
  • an ingredient for freezing the metal pieces is introduced, such as liquid nitrogen; it is sprayed directly onto the metal pieces. Mere contact of the liquid nitrogen with the scrap pieces will freeze them instantly.
  • the liquid nitrogen should be applied uniformly throughout its path to the point of impaction.
  • the ball milling elements are motivated preferably by rotation of the housing to contact and impact the frozen pieces of scrap metal causing them to fracture and be comminuted. Such impaction is carried out to apply a sufficient fracturing force for a sufficient period of time and rate to reduce said scrap pieces to a powder form.
  • the resulting powder will be layered or flake in configuration and typically have both coarse and fine powder proportions.
  • a typical screen analysis for a cryogenic powder would be as follows (for a 100 gm. sample):
  • the method is varied in another important aspect: the compact or briquetted product is subjected to sintering.
  • This treatment can be carried out in a conventional sintering furnace with heating to a temperature preferably about 1093°C (2000 0 F).
  • the temperature to which the briquetted or compact is heated should be at least to the plastic region for the metal constituting the powder.
  • a controlled or protective atmosphere may be maintained in the furnace, preferably consisting of inert or reducing gases.
  • Table I Test results to support the above methods are depicted in Table I.
  • an iron powder specimen identified as Atomet 28 was employed which has a chemistry of 99.8% Fe 0.05% C and an average particle size of 70-80 microns.
  • the second powder specimen consisted of carbonyl powder, having a chemistry of 99.9% Fe 0.1% C and a particle size range of 4-5 microns.
  • Tin was employed in an amount- of 2.5% weight percentage of the powder mass. This required ball milling to be carried out for a period of 48 hours to achieve a coating thickness of about 0.1 micron.
  • Each powder specimen was heated to a temperature level of 245°C (473°F).

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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)

Claims (8)

1. Verfahren zum Herstellen eines Metall-- pulver-Festkörpers, bei dem Metallpulver in Gegenwart eines Metalls mit niedrigem Schmelzpunkt bei einer Temperatur verfestigt wird, die zum Schmelzen des Metalls mit niedrigem Schmelzpunkt ausreicht, dadurch gekennzeichnet, daß das Metallpulver in Gegenwart von 1 bis 5 Gewichtsprozent des Metalls mit niedrigem Schmelzpunkt verfestigt wird, daß das Metallpulver unter einem Druck von höchstens 4725 kg/cm2 verfestigt wird und daß die Metallpulverteilchen durch sogenannte Trockenschlagbeschichtung mit dem bei niedriger Temperatur schmelzenden beschichtet werden.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Trockenschlagbeschichtung durch Kugelmahlen mit Mahlelementen ausgeführt wird, die aus dem Metal mit niedrigem Schmelzpunkt bestehen bzw. es tragen.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das Metallpulver aus Eisen besteht und mit 2 bis 4 Gewichtsprozent des Metalls mit niedrigem Schmelzpunkt beschichtet wird.
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Metal mit niedrigem Schmelzpunkt aus Zinn, einer Kupfer-Zinnlegierung, einer Kupfer-Bleilierung und aus Blei ausgewählt wird.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß das Metal mit niedrigem Schmelzpunkt aus Zinn besteht.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Metallpulver bei einer Temperatur zwischen 230 und 345°C verfestigt wird.
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Teilchengröße des Metallpulvers zwischen 60 und 120 Mikron beträgt.
8. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet daß der Metallpulver-Festkörper gesintert ist.
EP79302649A 1978-11-24 1979-11-21 Pulvermetallurgisches Verfahren zur Herstellung von Formkörpern Expired EP0011981B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US96353978A 1978-11-24 1978-11-24
US963539 1978-11-24

Publications (2)

Publication Number Publication Date
EP0011981A1 EP0011981A1 (de) 1980-06-11
EP0011981B1 true EP0011981B1 (de) 1983-12-14

Family

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Family Applications (1)

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EP79302649A Expired EP0011981B1 (de) 1978-11-24 1979-11-21 Pulvermetallurgisches Verfahren zur Herstellung von Formkörpern

Country Status (4)

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EP (1) EP0011981B1 (de)
JP (1) JPS5573801A (de)
CA (1) CA1151384A (de)
DE (1) DE2966491D1 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2477926A1 (fr) * 1980-03-12 1981-09-18 Alliages Frittes Sa Procede de fabrication de pieces a partir de poudres metalliques, frittees a basse temperature
DE3484566D1 (de) * 1983-06-02 1991-06-13 Kawasaki Steel Co Zinn enthaltendes eisenpulver und dessen herstellungsverfahren.
JPS613801A (ja) * 1984-06-18 1986-01-09 Kawasaki Steel Corp スズ含有鉄系複合粉末およびその製造方法
WO1996001407A1 (en) * 1994-07-06 1996-01-18 Lockheed Martin Energy Systems, Inc. Non-lead, environmentally safe projectiles and method of making same
US7754633B2 (en) * 2008-07-22 2010-07-13 Harbison-Walker Reeractories Company Chromia-alumina refractory
CN103042205A (zh) * 2012-12-18 2013-04-17 株洲弘通硬质合金有限公司 一种空心难熔金属及合金喷涂粉末的制备方法
US11019928B2 (en) 2016-06-10 2021-06-01 Okamura Corporation Armrest and chair

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1793757A (en) * 1927-02-05 1931-02-24 William H Smith Process of uniting iron with other metals and elements
US1986197A (en) * 1932-03-10 1935-01-01 Harshaw Chem Corp Metallic composition
US3520680A (en) * 1968-07-22 1970-07-14 Pfizer & Co C Process of producing steel
JPS5441969B2 (de) * 1972-06-29 1979-12-11
US4050933A (en) * 1973-02-21 1977-09-27 Stanadyne, Inc. Impervious metal object and method of making the same
FR2304678A1 (fr) * 1975-03-21 1976-10-15 Ugine Aciers Nouveau procede d'elaboration d'aciers a usinabilite amelioree a partir de metal divise
JPS51143871A (en) * 1975-06-06 1976-12-10 Hitachi Metals Ltd Electric contact material manufacturing method

Also Published As

Publication number Publication date
EP0011981A1 (de) 1980-06-11
JPS5573801A (en) 1980-06-03
DE2966491D1 (en) 1984-01-19
JPS5653601B2 (de) 1981-12-19
CA1151384A (en) 1983-08-09

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