Properties of Powder Metallurgy Steel Forgings
ROCK ISLAND ARSENAL IL GENERAL THOMAS J RODMAN LAB
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The effects of processing variables on the mechanical properties of heat-treated powder metallurgy PM steel forgings were determined. Three powders, AISI 4650 and modified AISI 4600 powders blended with graphite to yield 4640 composition, and AISI 4650 powder, were compacted into preforms and hot forged in a warm, closed die. Variables studied were preform density, method of lubrication, preform sintering time, temperature and atmosphere, forging pressure 20 and 40 tsi and temperature 1850F, 2000F and 2200F, and forging ratio 0.85 and 0.95. Relationships between interconnected porosity and total porosity for the various preform densities were determined. High density compacts required higher sintering temperatures due to the restricted mobility of the reducing gases in the pores. Die wall lubrication was comparable to admixed lubrication, and it simplified powder mixing and preform sintering operations.
- Properties of Metals and Alloys
- Fabrication Metallurgy