PRODUCTION OF POWDER METAL FORGED PARTS HAVING EXCELLENT HARDENABILITY AND TOUGHNESS

摘要

PURPOSE:To produce powder metal forged parts having excellent hardenability and toughness in the stage of producing the powder metal forged parts by using the Cr-Mn low alloy steel powder of ultra low oxygen produced by an oil spraying method for the raw material, subjecting green compacts to a water infiltration treatmnt and decarburizing the green compacts in the stage of sintering. CONSTITUTION:The melt of inexpensive Cr-Mn alloy steel having excellent hardenability is pulverized by an oil spraying method using nonpolar solvents or mineral oils, vegetable oils, etc. The powder is degreased and in that state the powder is molded under pressure without decarburizing and annealing to produce green compacts. The green compacts are subjected repeatedly to water infiltration and drying to control the content of oxygen up to the content necessary for decarburization. Thereafter the green compacts are heated and sintered in an inert gaseous atmosphere, and are then decarburized at the oxygen content controlled in said sintering stage; thereafter the temp. is reduced down to the forging temp. at which the green compacts are forged. The powder metal forged parts having excellent hardenability and toughness are produced.