In order to develop a new heat resisting cast steel which has an excellent creep rupture properties and is free from the precipitation of sigma phase at the temperature range of 700°C to 800°C, the effects of Nb, Mo, W, and C on creep and creep rupture properties were studied on 0.45C-20Cr-25Ni cast steel.
The tensile properties at room temperature were not affected so much by alloying elements. The creep rupture strength became higher with increasing the amount of alloying elements but the excessive addition led to lower creep rupture strength at 700°C. The creep strength, however, became lower with increasing alloying elements. Thus, the creep rupture strength did not correspond to the creep strength. Creep rupture elongation became higher with increasing alloying elements. These results were attributed to the difference in precipitation morphology of eutectic carbide. From the present work, 0.45C-20Cr-25Ni-2Nb-2Mo-2W cast steel was found to have an excellent creep rupture properties.
