Study on Carbides in High-C High-V High-Speed Steel

In order to investigate the several characteristics of high-speed steels, which were made in our works, we isolated carbides in steel by electrolysis, and studied the composition, the crystal structure and the shape of carbides by chemical and X-ray analysis, electron microscopy etc. This report, especially lays stress on the relation of cutting durability and carbides in high-C high-V high-speed steel. The results obtained were as follow: (1) The contents of carbides in annealed state was about 20% and existed in three types of carbides, M6C, MC and M23C6. The content of carbide MC in this steel was several times that in other high-speed steel. (2) In quenched state, the amount of insoluble carbides was about 8%. These carbides consisted nearly of MC alone. The remainder of carbides was only M6C, (3) With the progress of tempering, the carbide contents increased, especially suddenly at 575°C. But up to 650°C, the weight percentages between the two types of carbides, MC and M6C, remained unchanged. (4) This high-C high V (XVC1) steel, in spite of low W and no Co contents, indicated an as good cutting durability as W-Co (X00) steel. We consider, this is due to the presence of a number of small and hard carbides MC grains effectively serving for the purpose.