| 摘要 |
A cold rolled steel sheet, and a method of manufacturing the same, designed to have aging resistance and excellent formability suitable for use in automobile bodies, electronic appliances, and the like. The cold rolled steel sheet comprises in weight %: 0.003% or less of C, 0.003˜0.03% of S, 0.01˜0.1% of Al, 0.02% or less of N, 0.2% or less of P, at least one of 0.03˜0.2% of Mn and 0.005˜0.2% of Cu, and a balance of Fe and other unavoidable impurities. When the steel sheet comprises one of Mn and Cu, the composition of Mn, Cu, and S satisfies at least one relationship: 0.58*Mn/S≦10 and 1≦0.5*Cu/S≦10, and when the steel sheet comprises both Mn and Cu, the composition of Mn, Cu, and S satisfies the relationship: Mn+Cu≦0.3 and 2≦0.5*(Mn+Cu)/S≦20. Participates of MnS, CuS, and (Mn, Cu)S in the steel sheet have an average size of 0.2 μm or less. Since carbon content in a solid solution state in a crystal grain is controlled by fine precipitates of MnS, CuS, or (Mn, Cu)S, the steel sheet has enhanced aging resistance and formability, and has excellent yield strength and strength-ductility. |
| 主权项 |
1. A cold rolled steel sheet for an automobile having aging resistance, comprising in weight %: 0.003% or less of C; 0.005˜0.03% of S; 0.01˜0.1% of Al; 0.02% or less of N; 0.2% or less of P; 0.05˜0.2% of Mn; 0.2˜1.2% Cr and the balance of Fe and other unavoidable impurities, wherein a composition of Mn and S satisfies the relationship: 0.58*Mn/S≦10, wherein the steel sheet comprises precipitates of MnS having an average size of 0.2 μm or less, and wherein the steel has a yield strength of 197 MPa or more, an rm-value of 1.47 or more, and an aging index of 27 MPa or less. |
