Patent ID: 7074283
Filing Date: 2006-07-11
Classification: C22C

Abstract:
1. A low alloy steel, characterized by consisting of, by mass %, C: 0.2–0.55%, Si: 0.05–0.5%, Mn: 0.1–1%, S: 0.0005–0.01%, O(Oxygen): 0.0010–0.01%, Al: 0.005–0.05%, Ca: 0.0003–0.007%, Ti: 0.005–0.05%, Cr: 0.1–1.5%, Mo: 0.1–1% and Nb: 0.005–0.1%, and the balance Fe and impurities; and also characterized by the impurities whose contents are restricted to P≦0.03% and N≦0.015%; and further characterized by containing composites of inclusions of not greater than 7 μm in major axis with an appearance frequency of not less than 10 pieces of composites per 0.1 mm 2 of the steel cross section, wherein the composite comprises an outer shell of carbonitride of Ti and/or Nb surrounding a nucleus of oxysulfide of Al and Ca.