Patent ID: 9051634
Filing Date: 2015-06-09
Classification: C21C,C21D,C22C

Abstract:
1. A steel sheet in which chemical components of a steel include, by mass %: 0.5% to 0.8% of C; 0.15% to 0.60% of Si; 0.40% to 0.90% of Mn; 0.010% to 0.070% of Al; 0.001% to 0.010% of Ti; 0.30% to 0.70% of Cr; 0.0005% to 0.0030% of Ca; 0.0003% to 0.0050% of REM; 0.020% or less of P; 0.0070% or less of S; 0.0040% or less of O; and 0.0075% or less of N, the balance composed of Fe and unavoidable impurities, wherein the amounts of the respective elements in the chemical components, which are represented by mass %, satisfy the following Expression 1 and Expression 2, and the steel contains a Ti-included-carbonitride as an inclusion, and a number density of the Ti-included-carbonitride having a long side of 5 μm or more is 3 pieces/mm