The free cutting toll steel which is superior in the heatproof treatment deformans and finishing property and the die null mass which uses

摘要

PROBLEM TO BE SOLVED: To provide free-cutting tool steel which has a good machinability and a mechanical property, wherein the resistance to heat-treatment deformation and the surface treatment characteristic are improved, and a metal mold.;SOLUTION: The free-cutting tool steel comprises, by mass, 0.1-0.6% Si, 0.1-1.2% Mn, 1.2% V and 0.01-0.3% Nb and comprises Cr, C and at least one chosen from Mo and W, provided that (Cr+5.9×C) is 11.1-12.7%, (Cr-4.2×C) is ≤5.2%, (Cr-6.3×C) is ≥2.2 and (Mo+1/2W) is 0.6-1.25%. Optionally, the steel further contains ≤0.12% S and ≤100 ppm Ca and/or further contains ≤1% Ni and ≤0.6% Al. The metal mold is made of the steel, is quenched and tempered and has a surface-hardened layer.;COPYRIGHT: (C)2005,JPO&NCIPI