HIGH-STRENGTH UNTEMPERED STEEL FOR FRACTURE SPLITTING AND STEEL COMPONENT FOR FRACTURE SPLITTING

摘要

High strength fracture splitting use non-heat treated steel containing, by mass%, C: 0.23 to 0.35%, Si: 0.70 to 1.30%, Mn: 0.76 to 1.17%, P: 0.040 to 0.080%, S: 0.040 to 0.118%, Cr: 0.05 to 0.20%, Al: 0.010% or less, V: 0.27 to 0.45%, and N: 0.0050 to 0.0145%, having a balance of Fe and unavoidable impurities, having values of three formulas limiting the composition of ingredients satisfying required values, ensuring hot ductility, and, when hot forged, then cooled by air cooling or air blast cooling, forming a ferrite-pearlite structure having a ferrite fraction of 60% or more, and a fracture splitting use steel part.