Synopsis: Particle size distributions, microstructures and residual gas contents of high speed steel powders, atomized by spraying water or argon gas have been investigated. The particle size distributions and the microstructures of the water-atomized powders are finer than those of the argon-atomized powders. Oxygen contents of the water-atomized powders are higher, but can be easily reduced by sintering in a vacuum furnace. In the argon-atomized powders, argon included in the powders are

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... ved. Sintered and hot-forged high speed steels of low oxygen contents have high transverse rupture strength and notch-toughness, because of their uniformly fine microstructures. Retained austenite is decreased and grinding is also relatively easy in the sintered and hot-forged high speed steels of fine microstructures.