HIGH-STRENGTH STEEL, AND CRANKSHAFT MANUFACTURED USING SAID HIGH-STRENGTH STEEL

摘要

An object of this invention is to provide a high-strength steel endowed with high fatigue strength while also having increased strength and toughness, and a crankshaft manufactured using this high-strength steel. The high-strength steel according to the invention contains 0.30 mass % or more and 0.50 mass % or less of C, more than 0 mass % and 0.15 mass % or less of Si, 0.80 mass % or more and 1.5 mass % or less of Mn, 0.8 mass % or more and 2.4 mass % or less of Ni, 1.0 mass % or more and 3.0 mass % or less of Cr, 0.35 mass % or more and 0.70 mass % or less of Mo, 0.10 mass % or more and 0.25 mass % or less of V and 0.001 mass % or more and 0.040 mass % or less of Al, with the balance being iron and inevitable impurities. The high-strength steel is mainly composed of martensit, wherein a Mn concentration in cementite is 0.90 mass % or more and 1.80 mass % or less, and a ratio of Mn content to Si content is 5.50 or more.