Hi-density forming process
AssigneeStackpole Limited
InventorsPeter Jones, Roger Lawcock
Life of this patent
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Abstract
A method for making a high density powdered metal article is provided. The composition consists of iron based powder, lubricant, graphite and ferro alloy additions. The composition is compacted in rigid tools at ambient temperature, sintered at high temperature and then formed in rigid tools at 40 to 90 tons per square inch to a density greater than 94% of theoretical. The high density article is then annealed. The final article demonstrates remarkable mechanical properties which are atypical of powdered metal components and approach those of wrought steel.
Claims16
A method of forming sintered powder metal articles to a high density by forming the sintered powder metal in a closed die cavity having a clearance for movement of said sintered powder metal to final shape with increased density after compression wherein the formed sintered powder metal part has a compressed length of approximately 3 to 30% less than the original length.
A method of forming sintered powder metal article by:
- (a) blending
- (i) carbon
- (ii) at least one ferro alloy powder selected from the group of ferro chromium, ferro manganese, ferro molybdenum, and
- (iii) a lubricant, with
- (iv) iron powder to form a blended mixture;
- (b) pressing said blended mixture to form said article;
- (c) sintering said article at a temperature greater than 1250.degree. C.;
- (d) forming said sintered article in a closed die cavity having a clearance so as to produce a formed sintered powder metal part having a compressed length of approximately 3 to 19% less than the original length when subjected to a pressure between 40 and 90 tons per square inch so as to increase the density of said formed sintered article;
- (e) annealing said formed sintered article at a temperature greater than 800.degree. C. in a reducing or carburizing atmosphere or vacuum.
A method of making a high density sintered powder metal article, comprising the steps of:
- (a) blending iron powder with ferro alloys, graphite and lubricant to provide a selected chemical composition for the finished article having at least one of the following:
- 0 to 0.5% carbon, 0 to 1.5% manganese, 0 to 1.5% molybdenum and to 1.5% chromium and the remainder iron powder with unavoidable impurities;
- (b) compacting the metal powder mixture in a rigid die to a density of approximately 90% of theoretical full density;
- (c) sintering the compacted article at a temperature greater than 1250.degree. C. in a reducing atmosphere or vacuum;
- (d) forming the sintered article in rigid tools at pressure in the range of 40 to 90 tons per square inch to a density in excess of 94% of theoretical full density by axial compression allowing radial expansion to decrease the axial length of the sintered article by approximately 3 to 30% of the original length.
- (e) annealing the high density article at a temperature greater than 800.degree. C. in a reducing or carburizing atmosphere or vacuum;
- where the total alloy composition is between 0 to 2.5% by weight to the total weight of sintered powder metal article.
Dependencies are inferred from the claim text.