| 摘要 |
PURPOSE:To produce a grain nonoriented electrical steel plate excellent in magnetic properties in a medium magnetic field and machinability and having high specific resistance value by working an Si-containing extremely low carbon steel into a plate at respectively specified temp. and rolling conditions and then performing dehydrogenation heat treatment, annealing, or normalizing according to plate thickness. CONSTITUTION:A slab of a steel for silicon steel having a composition containing, by weight, <0.008% C, 0.1-3.0% Si, <0.20% Mn, 0.02-0.2% P, <0.010% S, <0.040% Al, <0.004% N, <0.005% O, and <0.O002% H is subjected to heating up to 950-1150 deg.C before rolling. After high rolling shape ratio hot rolling including more than one rolling pass where rolling shape ratio A represented by an equation is regulated to >=0.6 is performed at >=800 deg.C, rolling of 35-70% cumulative reduction of area is successively exerted at <=800 deg.C to refine crystalline grains. A plate of >=50mm thickness is subjected to dehydrogenation heat treatment at 600-750 deg.C and, as necessary, to annealing at 750-1150 deg.C or normalizing at 910-1200 deg.C. A plate of <=50mm thickness is annealed at 750-1150 deg.C or normalized at 910-1200 deg.C. |
