| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high Si cold-rolled steel sheet having good chemical convertibility, even containing Si as 0.6% or higher.SOLUTION: A cold-rolled steel sheet has the component-composition composed by mass of 0.05-0.3% C, 0.56-3% Si, 1.0-3.0% Mn, ≤0.1% P, ≤0.05% S, 0.01-1% Al, ≤0.01% N, 0.0003-0.005% B and the balance Fe with inevitable impurities. When the cold-rolled steel sheet is continuously annealed, the steel sheet is heated by using a direct-firing burner of ≥0.95 in air-ratio at least 550°C or higher of the steel sheet temperature at the temperature-raising time, and then is heated up to 750°C or higher of the steel sheet temperature by using the direct-firing burner having an air ratio of ≤0.89. Thereafter, the steel sheet is soak-annealed in a furnace under gaseous atmospheric state of ((1-10 vol% H)+(balance Ngas)) at a dew-point of -25°C or lower. |
