Making of articles from metallic powder
OwnerRichard James Dain, Hugh Fordinventors
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Abstract
The invention relates to making articles from metallic powder, particularly of tool steel, alloy steel and stainless steel and cobalt based hard metal powders, of high density and quality. The powder is compacted to at least 65% density and heated in the compacted form in two stages, firstly to deoxidize it preferably to less than 400 p.p.m. oxygen content and secondly to sinter it at least at the solidus temperature of the powder to produce a compact of at least 98% relative density. Normally the powder is annealed before compaction to soften it to a condition in which it can be compacted at pressures of 15 to 40 t.s.i. to densities of at least 65%.
Claims17
A method of making a dense metal alloy product comprising the steps of:
- a. making powder by atomization of a melt of metal alloy;
- b. heating the powder in a sub-atomspheric pressure and cooling the powder at a controlled rate initially to deoxidize it and anneal it;
- c. compacting alloy powder and thereby forming a compact with a relatively density of at least 65%;
- d. heating said compact at a sub-atmospheric pressure but below the solidus temperature for at least half an hour in order to further reduce the oxygen content of the compact;
- and
- e. raising the temperature to a selected sinter temperature which is at least the solidus temperature of the alloy while maintaining a sub-atmospheric pressure and maintaining the temperature within .+-. 10.degree. C of the selected temperature for at least half an hour to sinter the compact and cause densification of the compacrt of at least 98% relative density.
A method of making a dense metal alloy article from metallic powder which comprises:
- 1. making powder by atomization of a melt of metal alloy;
- 2. heating the powder in a vacuum at a temperature above 1,000.degree. C for at least 2 hours and cooling the powder at a controlled rate initially to deoxidize it and anneal it;
- 3. adding a lubricant to the powder and subjecting it to a pressure in excess of 15 t.s.i. to form a compact with a relative density of at least 65%;
- 4. heat treating the compact in a vacuum in three stages of which:
- a. in one stage the compact is heated to 200.degree. to 600.degree. for at least half an hour until the lubricant is substantially all outgassed;
- b. in a second stage the compact is heated at a temperature 75.degree. to 150.degree. C below the solidus temperature of the powder for a period of at least 1/2 hour to reduce the oxygen content to below 400 p.p.m.
- c. in a third stage the compact is heated to a selected sinter temperature at least at the solidus temperature of the powder and maintained within .+-. 10.degree. C of the selected temperature for at least 1/2 hour to achieve a relative density of at least 98%.
Dependencies are inferred from the claim text.