EP1735477A2 - Making sintered, iron-based alloy parts by using boron-containing master alloys - Google Patents

Making sintered, iron-based alloy parts by using boron-containing master alloys

Info

Publication number
EP1735477A2
EP1735477A2 EP05717969A EP05717969A EP1735477A2 EP 1735477 A2 EP1735477 A2 EP 1735477A2 EP 05717969 A EP05717969 A EP 05717969A EP 05717969 A EP05717969 A EP 05717969A EP 1735477 A2 EP1735477 A2 EP 1735477A2
Authority
EP
European Patent Office
Prior art keywords
iron
boron
pressing
density
sintering
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.)
Withdrawn
Application number
EP05717969A
Other languages
German (de)
French (fr)
Inventor
Stephen Charles Mitchell
Miren Sarasola Inigeuz
Francisco Castro Fernandez
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.)
Schunk Sintermetalltechnik GmbH
AMES Group Sintering SA
Atomising Systems Ltd
Original Assignee
Schunk Sintermetalltechnik GmbH
Aleaciones de Metales Sinterizados SA AMES
Atomising Systems 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 Schunk Sintermetalltechnik GmbH, Aleaciones de Metales Sinterizados SA AMES, Atomising Systems Ltd filed Critical Schunk Sintermetalltechnik GmbH
Publication of EP1735477A2 publication Critical patent/EP1735477A2/en
Withdrawn legal-status Critical Current

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
    • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
    • 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
    • B22F3/02—Compacting only
    • B22F2003/023—Lubricant mixed with the metal powder
    • 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
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F2003/145—Both compacting and sintering simultaneously by warm compacting, below debindering temperature
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • This invention relates to a method of making high-density (>7.0g/ml) sintered, iron-based alloy parts using boron-containing Master Alloys, and to parts produced by
  • ferrophosphorous additions have been quite successful, but the resulting properties tend to be reduced by brittle networks of phosphide. Additionally, work with ferrophosphorous additions required sintering temperatures between 1290°C and 1380°C and ultrahigh carbon additions (0.8 to 2.0) to achieve near full density, as disclosed by US Patent 5,516,483. In the 1970s work in Germany on the use of MCM (metal carbide master alloys) showed great promise, but it was found that the additives, in the form of finely milled carbides of vanadium, chromium, molybdenum and manganese, were extremely abrasive and tool life was drastically degraded, making production uneconomic.
  • MCM metal carbide master alloys
  • a basic object of the invention is the provision of an improved method of making high-density (>7.0g/ml) sintered, iron-based alloy parts, and to parts produced by this method.
  • Summary of a First Aspect of the Invention According to a first aspect of the invention, there is provided method of making high-density (>7.0g/ml) sintered, iron-based alloy parts characterised by the steps of: (i) mixing an atomised boron-containing master alloy powder, or a plurality of master alloy powders at least one . of which is boron-containing, with a conventional iron or iron alloy powder; and (ii) pressing and sintering the mix to an increased density to produce the part required.
  • Summary of a Second Aspect of the Invention A second aspect of the invention is directed to high density, sintered, iron-based alloy parts produced by the above defined method. Advantages of the Invention
  • the invention provides a new concept where, instead of utilising milled powders as MA additives, an atomised, essentially spherical additive is used.
  • This allows the use of less hard a brittle alloys, as the atomising process does not, like milling, demand a brittle alloy be processed. It also reduces the abrasive nature of the resulting powders, as they do not have the sharp edges characteristic of a milled or ground product.
  • the alloying approach adopted has also been the subject of intensive research, and MA compositions including a significant level of boron have been developed. As a result it has been possible to reach sintered densities in the range 7.2-7.8 without resorting to forging, DPDS or to extremely high sintering temperatures.
  • a lubricant is added to the mix in conventional amounts as used in powder metallurgy technology.
  • the lubricant is a solid.
  • the lubricant is a liquid.
  • the lubricant is a solid dissolved in a liquid.
  • the master alloy powder(s) contains from 1-20% by wt boron.
  • the master alloy powder(s) has a mean particle size from 1-30 microns, preferably under 20 microns. Sintering is effected at temperatures in the range 1050°C to 1300°C, preferably below 1200°C.
  • Sintering is effected in a reducing, inert , or vacuum atmosphere. From ⁇ 6% by weight of atomised master alloy powder(s) is mixed with the conventional iron or low alloy powder.
  • the pressing is cold pressing.
  • the pressing is warm pressing ⁇ 300°C.
  • the pressed density of the part is 6.6-7.4g/ml.
  • the parts have a boron content above 0.1 % by wt.
  • the parts have a density from 7.2-7.8, preferably 7.4-7.6g/ml.

Abstract

A method of making high-density (>7.Og/ml) sintered iron-based alloy parts by using boron-containing Master Alloys comprises the steps of mixing an atomised, boron-containing master alloy powder, or a plurality of master alloy powders at least one of which is boron-containing, with a conventional iron or iron alloy powder; optionally adding graphite and a lubricant in conventional amounts as used in powder metallurgy technology; and pressing and sintering the mix to an increased density, preferably in a reducing, inert or vacuum atmosphere at 1050 to 1300°C, to produce the part required. The invention also includes parts produced by the above defined method.

Description

Title of the Invention Making sintered, iron-based alloy parts by using boron-containing Master Alloys
Field of the Invention This invention relates to a method of making high-density (>7.0g/ml) sintered, iron-based alloy parts using boron-containing Master Alloys, and to parts produced by
this method. Background of the Invention Structural parts of complex shape have been produced for over 50 years by powder metallurgy (PM). The simplest form of this process involves mixing a fine (<150microns) metal (normally iron) powder with a lubricant and also such alloying additions as graphite and copper, pressing a green compact in a die under axial loading, and sintering the resulting part in a reducing atmosphere, typically at around
1120°C. In 2000 this process in all its forms was used to produce about 500,000 tons of parts, the vast majority of which were used in the automobile industry. Growth of application of the process, which provides complex and precise parts at low cost, is limited by the porosity of the parts, which reduces their properties, especially their dynamic properties such as impact resistance and fatigue strength.
For this reason, applications are limited to less heavily loaded parts. To be applied in such parts as transmission gears for cars, a higher density than the currently achievable 7.0-7.2g/ml range is needed, together with suitable alloying to allow surface hardening and heat treatment. A number of methods have been proposed to achieve higher densities. In powder forging, the sintered part is heated and forged. This raises density to -100% of solid (~7.8g/ml) but at considerable cost and with some reduction of precision. It has found significant, but limited application as a result. It is also possible to take the sintered part and press it again to density, followed by a second sintering operation. This again increases costs, and cannot achieve full density, being limited to the range 7.2-7.4g/ml. The use of high temperature sintering, normally considered as temperatures above 1120°C, the practical limit for mesh-belt furnaces, has also been tried. Temperatures of 1200-1300°C have been used, but costs have been high and the improvements in properties modest. Temperatures of 1180-1250 °C are now in common use, but have not, in themselves, enabled the achievement of high density, high dynamic performance parts. The concept of adding a master alloy (MA) powder as a "sintering aid" to density the part is well known, and is widely used in the fabrication of tungsten heavy alloy, tungsten carbide etc. However attempts to apply it to iron powder parts have had limited success. The use of ferrophosphorous additions has been quite successful, but the resulting properties tend to be reduced by brittle networks of phosphide. Additionally, work with ferrophosphorous additions required sintering temperatures between 1290°C and 1380°C and ultrahigh carbon additions (0.8 to 2.0) to achieve near full density, as disclosed by US Patent 5,516,483. In the 1970s work in Germany on the use of MCM (metal carbide master alloys) showed great promise, but it was found that the additives, in the form of finely milled carbides of vanadium, chromium, molybdenum and manganese, were extremely abrasive and tool life was drastically degraded, making production uneconomic. In any case these works, aiming at obtaining high strength materials, used double press-double sinter (DPDS) or forging methods for consolidating the PM steels. Single press-single sinter (SPSS) did not lead to materials with higher densities than 7.2 g/cc. A recent report highlighting the use of several Master Alloys J was also directed towards the use of powder forging without attempting to reach high densities by SPSS.
Object of the Invention A basic object of the invention is the provision of an improved method of making high-density (>7.0g/ml) sintered, iron-based alloy parts, and to parts produced by this method. Summary of a First Aspect of the Invention According to a first aspect of the invention, there is provided method of making high-density (>7.0g/ml) sintered, iron-based alloy parts characterised by the steps of: (i) mixing an atomised boron-containing master alloy powder, or a plurality of master alloy powders at least one . of which is boron-containing, with a conventional iron or iron alloy powder; and (ii) pressing and sintering the mix to an increased density to produce the part required. Summary of a Second Aspect of the Invention A second aspect of the invention is directed to high density, sintered, iron-based alloy parts produced by the above defined method. Advantages of the Invention
The invention provides a new concept where, instead of utilising milled powders as MA additives, an atomised, essentially spherical additive is used. This allows the use of less hard a brittle alloys, as the atomising process does not, like milling, demand a brittle alloy be processed. It also reduces the abrasive nature of the resulting powders, as they do not have the sharp edges characteristic of a milled or ground product. The alloying approach adopted has also been the subject of intensive research, and MA compositions including a significant level of boron have been developed. As a result it has been possible to reach sintered densities in the range 7.2-7.8 without resorting to forging, DPDS or to extremely high sintering temperatures. Preferred or Optional Features of the Invention Before pressing and sintering, graphite is added to the mix in conventional amounts as used in powder metallurgy technology. Before pressing and sintering, a lubricant is added to the mix in conventional amounts as used in powder metallurgy technology. The lubricant is a solid. The lubricant is a liquid. The lubricant is a solid dissolved in a liquid. The master alloy powder(s) contains from 1-20% by wt boron. , The master alloy powder(s) has a mean particle size from 1-30 microns, preferably under 20 microns. Sintering is effected at temperatures in the range 1050°C to 1300°C, preferably below 1200°C. Sintering is effected in a reducing, inert, or vacuum atmosphere. From < 6% by weight of atomised master alloy powder(s) is mixed with the conventional iron or low alloy powder. The pressing is cold pressing. The pressing is warm pressing <300°C. The pressed density of the part is 6.6-7.4g/ml. The parts have a boron content above 0.1 % by wt. The parts have a density from 7.2-7.8, preferably 7.4-7.6g/ml.

Claims

1. A method of making high-density (>7.0g/ml) sintered, iron-based alloy parts characterised by the steps of: (i) mixing an atomised boron-containing master alloy powder, or a plurality of master alloy powders at least one of which is boron-containing, with a conventional iron or iron alloy powder; and (ii) pressing and sintering the mix to an increased density to produce the part required.
2. A method as claimed in Claim 1 , wherein before pressing and sintering, graphite is added to the mix in conventional amounts as used in powder metallurgy technology.
3. A method as claimed in Claim 1 or Claim 2, wherein before pressing and sintering, a lubricant is added to the mix in conventional amounts as used in powder metallurgy technology.
4. A method as claimed in Claim 3, wherein the lubricant is a solid.
5. A method as claimed in Claim 3, wherein the lubricant is a liquid.
6. A method as claimed in Claim 3, wherein the lubricant is a solid dissolved in a liquid.
7. A method as claimed in any preceding claim, wherein the master alloy powder(s) contains from .1-20% by wt boron.
8. A method as claimed in any preceding claim, wherein the master alloy powder(s) has a mean particle size from 1-30 microns, preferably under 20 microns.
9. A method in accordance with any preceding claim, wherein the sintering is effected at temperatures in the range 1050°C to 1300°C, and preferably below effected at temperatures in the range 1050°C to 1300°C, and preferably below 1200°C.
10. A method as claimed in any preceding claim, wherein sintering is effected in a reducing, inert or vacuum atmosphere.
11. A method in accordance with any preceding claim, wherein from <6% by weight of atomised master alloy powder(s) is mixed with the conventional iron or low alloy powder.
12. A method in accordance with any preceding claim, wherein the pressing is cold pressing.
13. A method in accordance with any preceding claim, wherein the pressing is warm pressing <300°C.
14. A method in accordance with any preceding claim, wherein the pressed density of the part is 6.6-7.4g/ml.
15. A high-density sintered iron based part made in accordance with the method of any preceding claim.
16. A part as claimed in Claim 15, having a boron content above 0.05% by wt.
17. A part as claimed in Claim 15 or Claim 16, having a density from 7.2-7.8, preferably 7.4-7.6g/ml.
EP05717969A 2004-04-02 2005-03-09 Making sintered, iron-based alloy parts by using boron-containing master alloys Withdrawn EP1735477A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0407539.6A GB0407539D0 (en) 2004-04-02 2004-04-02 Making sintered iron based alloy parts by using boron-containing master alloys
PCT/GB2005/000904 WO2005095661A2 (en) 2004-04-02 2005-03-09 Making sintered, iron-based alloy parts by using boron-containing master alloys

Publications (1)

Publication Number Publication Date
EP1735477A2 true EP1735477A2 (en) 2006-12-27

Family

ID=32247768

Family Applications (1)

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EP05717969A Withdrawn EP1735477A2 (en) 2004-04-02 2005-03-09 Making sintered, iron-based alloy parts by using boron-containing master alloys

Country Status (4)

Country Link
US (1) US20070292301A1 (en)
EP (1) EP1735477A2 (en)
GB (1) GB0407539D0 (en)
WO (1) WO2005095661A2 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6309215B2 (en) * 2013-07-02 2018-04-11 Ntn株式会社 Sintered machine part manufacturing method and mixed powder used therefor
CZ309485B6 (en) * 2020-10-19 2023-02-15 Ústav fyziky materiálů AV ČR, v. v. i Compacting powders by volumetric moulding

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3999952A (en) * 1975-02-28 1976-12-28 Toyo Kohan Co., Ltd. Sintered hard alloy of multiple boride containing iron
JPS61186454A (en) * 1985-02-15 1986-08-20 Mitsubishi Metal Corp Fe-base sintered alloy having superior corrosion and wear resistances
US4861373A (en) * 1985-07-15 1989-08-29 Scm Metal Products, Inc. Infiltrated powder metal part having improved impact strength tensile strength and dimensional control and method for making same
US4612048A (en) * 1985-07-15 1986-09-16 E. I. Du Pont De Nemours And Company Dimensionally stable powder metal compositions
FR2596067B1 (en) * 1986-03-19 1991-02-08 Metafram Alliages Fritte PROCESS FOR MANUFACTURING SINTERED RAPID STEEL PARTS
US5330792A (en) * 1992-11-13 1994-07-19 Hoeganaes Corporation Method of making lubricated metallurgical powder composition
US5872322A (en) * 1997-02-03 1999-02-16 Ford Global Technologies, Inc. Liquid phase sintered powder metal articles
US6485540B1 (en) * 2000-08-09 2002-11-26 Keystone Investment Corporation Method for producing powder metal materials

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2005095661A2 *

Also Published As

Publication number Publication date
US20070292301A1 (en) 2007-12-20
WO2005095661A2 (en) 2005-10-13
WO2005095661A3 (en) 2006-08-24
GB0407539D0 (en) 2004-05-05

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