FREE-CUTTING HOT TOOL STEEL

PROBLEM TO BE SOLVED: To provide a hot tool steel combining machinability with toughness and having low anisotropy by utilizing difficult-to-elongate inclusions (CaSe) as a chip breaker at cutting thereby reducing anisotropy in heat check resistance and mechanical properties. SOLUTION: The hot tool steel has a composition consisting of, by mass, 0.15 to 0.6% C, 0.1 to 1.5% Si, 0.1 to 0.7% Mn, 1.5 to 6.0% Cr, 0.05 to 1.2% Ni, 0.0003 to 0.1% Ca, 0.0003 to 0.1% Se, either or both of W and Mo within the range satisfying Mo/W=0.5 to 2.5, either or both of V and Nb within the range satisfying V/Nb=0.1 to 2.0, and the balance Fe with inevitable impurities. COPYRIGHT: (C)2005,JPO&NCIPI