| 摘要 |
PROBLEM TO BE SOLVED: To produce a grain-oriented silicon steel sheet extremely high in magnetic flux density by regulating the average grain size of primarily crystallized grains before final finish annealing in a steel slab having a specified componental compsn. and specifying nitriding treatment till the start of secondary recrystallization in final finish annealing after hot rolling. SOLUTION: At the time of producing a grain-oriented silicon steel sheet from a slab contg., by weight, 0.025 to 0.075% C, 2.5 to 4.5% Si, 0.010 to 0.060% acid soluble Al, 0.0010 to 0.0130% N, and the balance Fe, the coiling temp. after the completion of hot rolling is regulated to 650 deg.C. The coil after coiling is subjected to forced cooling at a cooling rate more than that of air cooling to regulate the recrystallizing rate in the center of the sheet thickness of the hot rolled sheet to <=95%, and the average grain size of primarily recrystallized grains till the start of final finish annealing after the completion of decarburizing annealing is regulated to 18 to 35μm. Next, till the start of secondary recrystallization in final finish annealing after the hot rolling, the steel sheet is subjected to nitriding treatment with >=0.0020% by increasing the amt. of nitrogen, and in the case of temp. rising of 900 to 1200 deg.C in the final finish annealing, annealing is executed in an annealing atmosphere under >=15% partial pressure. |
