High speed tool steel and its manufacturing method
AssigneeHitachi Metals, Ltd.
InventorsShiho Fukumoto, Keiji Inoue
Life of this patent
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Abstract
A high speed tool steel, which is high in impact value and free from variations in tool performance, comprising, by mass %, of: 0.4≦C≧0.9; S1≦1.0; Mn≦1.0; 4≦Cr≧6; 1.5-6 in total of either or both of W and Mo in the form of (1/2 W+Mo) wherein W≦3; 0.5-3 in total of either or both of V and Nb in the form of (V+Nb); wherein carbides dispersed in the matrix of the tool steel have an average grain size of ≦0.5 μm and a dispersion density of particles of the carbides is of ≧80×103 particles/mm2.
Claims10
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 (1/2 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 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 80×103 particles/mm2.
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 (1/2 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 an ingot of the steel is prepared by 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.
Dependencies are inferred from the claim text.