The steel and its manufacturing method for hot carburization and the element forma item and its carburization hardening mannered null mass which for hot carburization are superior in resistance grain

摘要

PROBLEM TO BE SOLVED: To provide a steel for high-temperature carburization, which is a steel to be hot-forged, cold-forged, carburized and quenched, and can stably prevent its crystal grain from coarsening when carburized at a high temperature of 950°C or higher.;SOLUTION: The steel for high-temperature carburization comprises 0.1-0.35% C, at most 0.6% Mn, by mass%, while controlling a Mn content [Mn] so as to satisfy expression (1): [Mn]2.0-31/8×[C]-3/16×[Cr]-11/16×[Ni]-[Mo], 0.02-0.05% Al, 0.01-0.02% N, one or more elements selected from among Si, Cr, Ni, Mo and B, and the balance Fe with unavoidable impurities; and has a quenched hardness of 20 to 45 in HRC at a 1/2 inches distant position from a quenched end.;COPYRIGHT: (C)2006,JPO&NCIPI