Extrusion Forming of SKH51 High Speed Steel Fine Powderwax Mixtures

Abstract

SKH51 high speed steel powders with the specific surface area diameter of 3-6μmand the tap density ratio of 53% and over were produced by the super high pressure water atomization.
With the use of Acrawax C as the binder of these powders, the extrusion properties of the mixture, dewaxing conditions and sintering properties of compacts were examined. Powders mixed with 4.5-6.0 mass% wax showed the apparent viscositiy of 3-5*10³ Pa s at the shear rate of 10³S^-1. Compacts contained the closed porosity (εc) of 4-5%. these pores (mean radious r, surface tensionγLV) induced the hydrostatic pressure ∞(-2γLV/r)εc to the outer surface of the compact, then the wire shape resulted to be held with a suitable accuracy. Farther additions of the wax led the mixture to flow under gravity. The wax of the compact removed without any crack formations at the heating rate of 0.17K/s.Dewaxed compacts showed good sintering properties.