抄録
Green and tap densities of atomized high speed steel powders (JIS SKH 57) are measured. The shapes of the powders are spherical in gas atomization and irregular in water atomization. The densities are lower in the water-atomized powders than in the gas-atomized ones. Pulverization of the water-atomized powders increases the densities. Compacting press also increases the densities of the water-atomized powders. However, the densities of the water-atomized powders are difficult to approach to the tap density of the gasatomized powders.
Hot isostatic pressing, 113 MPa is applied at 1150°C in order to sinter densely the water-atomized powders, gas-atomized powders, and their mixture. Transverse rupture strength have been investigated in the dense specimens subjected to heat-treatment for hardening. The strength level of the specimens produced by using the water-atomized powders is much higher than that of the specimens produced by using the gas-atomized powders. It is also observed that adding the gas-atomized powders to the water-atomized powders causes the decrease in strength level.
Strength level is greatly increased by hot isostatic pressing and subsequent hot forging. However, the strength level of the dense specimens of the gas-atomized powders can not be increased satisfactorily without destroying the spherical forms by giving a great forging ratio.
