The effect of W and V on the high temperature strength properties of 12% Cr-15% Mn austenitic steels was studied from the view point of precipitation hardening and internal stress. The contribution of W addition to the tensile and creep-rupture strength was not so large. By contrast the combined addition of W and V increased the strengthes considerably. These are resulted from the precipitation of fine vanadium nitride (VN) within grains and the enhancement of M23C6 type carbide precipitation at grain boundaries. The V added material had large internal stress value which is considered to be due to dislocation movement disturbed by fine vanadium nitrides.
