Strain relief annealing non-oriented silicon steel sheet excellent magnetic properties and its manuf

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PROBLEM TO BE SOLVED : To provide a nonoriented silicon steel sheet having excellent magnetic properties after stress relieving annealing at a low cost, while suppressing the increase in Ti as possible, by reducing both S and Ti exerting adverse influence on grain growth so as to be made harmless. SOLUTION : The nonoriented silicon steel sheet has a composition comprising ≤3.5% Si, 0.2 to 2.0% Mn, 0.1 to 3.0% Al, ≤0.0020% C, ≤0.0020% Ti and ≤0.0015% S, and the balance Fe with inevitable impurities, and in which the content of S as MnS (S forming MnS) before stress relieving annealing is ≥0.0005% by mass%, and the MnS present before stress relieving annealing forms composite precipitates with Ti precipitates in a piece ratio of ≥10%. Regarding its production method, after componential regulation in steel making, desulfurization treatment is not performed by the addition of desulfurization flux, Ca alloys, Mg alloys and rare earth metals. Further, the basicity of ladle slag after vacuum degassing treatment and before the componential regulation is controlled to ≥3.0, and also, the concentration of TiO2is controlled to ≤0.2%. Further, slag heating temperature before hot rolling is controlled to 1, 000 to 1, 100°C, and hot rolled sheet annealing temperature is controlled to ≤1, 100°C. COPYRIGHT : (C)2005, JPO&NCIPI