Patent ID: 8608874
Filing Date: 2013-12-17
Classification: C21D,C22C,F16F

Abstract:
1. Spring steel comprising: a chemical composition including, C: greater than 0.35 mass % and less than 0.50 mass %, Si: greater than 1.75 mass % and equal to or less than 3.00 mass %, Mn: 0.2 mass % to 1.0 mass % (inclusive of 0.2 mass % and 1.0 mass %), Cr: 0.01 mass % to 0.04 mass % (inclusive of 0.01 mass % and 0.04 mass %), P: 0.025 mass % or less, S: 0.025 mass % or less, Mo: 0.1 mass % to 1.0 mass % (inclusive of 0.1 mass % and 1.0 mass %), O: 0.0015 mass % or less, and the balance as incidental impurities and Fe; and microstructure with martensite fraction of 90% or more, wherein a PC value calculated by Formula (1) below is greater than 3.3 and equal to or less than 8.0, and the spring steel has tensile strength of 1900 MPa or more, wherein [brackets] denote the content of an element in the brackets (in mass %).