STEEL FOR CASE HARDENING HAVING EXCELLENT COLD WORKABILITY AND COARSE GRAIN PREVENTION PROPERTY WHEN CARBURIZED, AND PRODUCTION METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a steel for case hardening which exhibits improved cold workability and prevents the occurrence of coarse grains when carburized, and to provide a production method therefor.;SOLUTION: A slab produced by a process where steel having a composition comprising, by mass%, 0.1 to 0.3% C, 0.01 to 0.15% Si, 0.2 to 0.65% Mn, 0.005 to 0.15% S, 0.4 to 1.25% Cr, 0.0005 to 0.005% B, 0.015 to 0.05% Al, and 0.03 to 0.15% Ti, a restricted content of N, P and O and the balance iron with inevitable impurities is cast, and is thereafter subjected to blooming without being cooled to an A3 point or below is hot-rolled into a wire rod or a bar steel under the conditions where the heating temperature is controlled to 900 to 1,070°C, the finishing temperature is controlled to 800 to 970°C, and successively to the hot rolling, slow cooling is performed at a cooling rate of ≤1°C/s in the temperature range of 800 to 500°C.;COPYRIGHT: (C)2004,JPO&NCIPI