High speed tool steel having superior hardness by controlling Co and Si content and method for manufacturing the same

摘要

PURPOSE: A high speed tool steel containing trace of cobalt is provided which controls hardness according to hardening temperature by controlling Co content and improves hardness by adding Si at the same time, and a method for manufacturing the same is provided. CONSTITUTION: The high hardness high speed tool steel containing trace of cobalt by controlling Co and Si contents comprises 0.75 to 1.1 wt.% of C, 0.1 to 1.0 wt.% of Si, 0.5 wt.% or less of Mn, 3.7 to 4.5 wt.% of Cr, 0.30 wt.% or less of Ni, 0.3 to 0.8 wt.% of Co, 4.5 to 5.5 wt.% of Mo, 5.5 to 6.8 wt.% of W, 1.7 to 2.2 wt.% of V, 0.6 wt.% or less of Cu and a balance of Fe and other inevitable impurities, wherein the high speed tool steel comprises 0.32 to 1.0 wt.% of Si, and wherein the high speed tool steel has 64 or more of Rockwell hardness. The method for manufacturing the high hardness high speed tool steel containing trace of cobalt by controlling Co and Si contents comprises the process of performing hot working on the homogenization treated steel slab by homogenization treating a steel slab comprising 0.75 to 1.1 wt.% of C, 0.1 to 1.0 wt.% of Si, 0.5 wt.% or less of Mn, 3.7 to 4.5 wt.% of Cr, 0.30 wt.% or less of Ni, 0.3 to 0.8 wt.% of Co, 4.5 to 5.5 wt.% of Mo, 5.5 to 6.8 wt.% of W, 1.7 to 2.2 wt.% of V, 0.6 wt.% or less of Cu and a balance of Fe and other inevitable impurities at a temperature of 1,100 to 1,150 deg.C.