한국주조공학회

Highly alloyed high speed tool steels(ASP steels) were rapidly solidified by melt spinning process, and the microstructures of melt spun tool steel ribbons were examined by optical microscopy and transmission electron microscopy with energy dispersive x-ray spectroscope. The microstructure of melt spun tool steel ribbon was found to be consisted of δ}-ferrite cells surrounded by austenite and V-rich MC carbides. The size of δ-ferrite cells and intercellular MC carbides were about 0.4μм or less and 30nm or less, respectively. From the melt spun tool steel ribbons, only the MC type carbide phase was observed, instead of M_2C, M_{23}C_6 and M_6C carbides which were generally observed in other rapidly solidified high speed steels. Such a change in type of carbide phase formed could be attributed to the increase in alloying content of vanadium and carbon. However, changes in microsturcture of melt spun tool steels with alloying content of cobalt, vanadium and carbon were not observed.