The gold model steel null mass which is superior in thermal

摘要

PROBLEM TO BE SOLVED: To provide a die steel in which heat checks and water-cooled hole cracks are suppressed by increasing its thermal fatigue properties and softening resistance, and capable of elongating a die life.;SOLUTION: A steel having a composition comprising, by mass, 0.1 to 0.6% C, 0.01 to 0.8% Si, 0.1 to 2.5% Mn, 0.01 to 2.0% Cu, 0.01 to 2.0% Ni, 0.1 to 2.0% Cr, 0.01 to 2.0% Mo, one or more selected from V, W, Nb and Ta by 0.01 to 2.0% in total, 0.002 to 0.04% Al, 0.002 to 0.04% N and ≤0.005% O, and the balance Fe with inevitable impurities is soaked at 1,010 to 1,050°C for 30 min, is quenched at 30°C/min, and is further subjected to tempering for 30 hours one time. In this state, the steel satisfies the following inequalities (1), (2) and (3): 30≤HRC^600°C≤55: inequality (1), -10.0≤HRC^600°C-HRC^550°C: inequality (2) and 30≤λ^RT(thermal conductivity): inequality (3).;COPYRIGHT: (C)2008,JPO&INPIT