Patent ID: 7754032
Filing Date: 2010-07-13
Classification: C21D,C22C

Abstract:
1. A method for manufacturing a high speed tool steel comprising, by mass percentage, a basic composition of: a 0.4-0.9% of C; an equal to or less than 1.0% of Si; an equal to or less than 1.0% of Mn; a 4-6% of Cr; a 1.5-6% in total of either or both of W and Mo in the form of (½ W+Mo) wherein the amount of W is not more than 3%; and, a 0.5-3% in total of either or both of V and Nb in the form of (V+Nb), wherein the tool steel is formed by an ingot which is subjected to a remelting process, heated to a temperature of from 1200° C. to 1300° C., subjected to a soaking process, and then cooled down to a temperature of equal to or less than 900° C. at a cooling rate of equal to or more than 3° C./minute in surface temperature of the ingot, wherein after completion of the soaking and the cooling process of the ingot, the ingot is subjected to a hot working process, and then subjected to quenching and tempering processes, and wherein an average grain size of precipitated carbides dispersed in the matrix of the steel is equal to or less than 0.5 μm and a dispersion density of the carbides is equal to or more than 80×10