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.

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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)

Applications Claiming Priority (2)

Publications (1)

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• 2004
  • 2004-04-02 GB GBGB0407539.6A patent/GB0407539D0/en not_active Ceased
• 2005
  • 2005-03-09 US US10/599,298 patent/US20070292301A1/en not_active Abandoned
  • 2005-03-09 WO PCT/GB2005/000904 patent/WO2005095661A2/en active Application Filing
  • 2005-03-09 EP EP05717969A patent/EP1735477A2/de not_active Withdrawn

Non-Patent Citations (1)

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