LOW-ALLOY HIGH-SPEED TOOL STEEL AND ITS PRODUCTION

摘要

PURPOSE:To manufacture a low-alloy high-speed tool steel excellent in wear resistance and impact resistance by subjecting a steel ingot having a specific composition consisting of C, Si, Mn, Cr, W, Mo, V, Nb, and Fe to specific diffusion heat treatment before or after hot working. CONSTITUTION:A steel ingot having a composition which consists of, by weight, 0.7-0.85% C, 0.8-2.2%, preferably 1.2-2.2%, Si, =0.6% Mn, 3.0-5.0% Cr, =3.0% W, 1.0-5.0% Mo, 0.5-1.5% V, 0.1-1.0% Nb, and the balance Fe with impurity elements and further contains, if necessary, =8% Co and/or 0.02-0.2% of one or more elements among Al, La, Ce, and Y and in which W+2Mo=5-10% is satisfied and the contents of Ti, N, S, and O are regulated to =0.02%, =0.006%, =0.004%, and =40ppm, respectively, is heated and held at 1150-1190 deg.C for 5-40hr in the stage before or after hot working to undergo diffusion heat treatment. By this method, the low-alloy high-speed tool steel of about 62-64 HRC excellent in wear resistance and having high toughness can be obtained. By using this tool steel, the service life of a forging tool can be remarkably improved.