HIGH-CARBON HOT ROLLED STEEL SHEET HAVING EXCELLENT QUENCH-HARDENING AND BLANKING PROPERTIES AND PRODUCTION THEREOF

摘要

PURPOSE: To extremely rapidly improve not only a quench-hardening property, toughness and cold workability but a precision blanking property which is heretofore of a problem. ;CONSTITUTION: This steel sheet is composed of 0.2 to 1.3wt.% C, 0.1 to 1.0wt.% Si, 0.05 to 2.0wt.% Mn, 0.01 to 0.2wt.% Al, ≤0.05wt.% S, ≤0.05wt.% P and ≤0.05wt.% N and consists of the balance Fe and inevitable impurities. The steel structure is formed of a fine carbide dispersed structure finely and uniformly dispersed with spheroidized carbide of a spheroidization rate of ≥90% and a grain size of ≤0.05μm in ferrite in the region of the surface layer part of the thickness directions of ≥1/10 and ≤1/4 respectively in the front and rear surfaces of the steel sheet. On the other hand, the other regions are formed of a pearlite structure.;COPYRIGHT: (C)1996,JPO