High-strength cold-rolled steel sheet having excellent bake hardenability, the manufacturing method of the molten coated steel sheet and cold rolled steel

摘要

Topic This invention is something regarding the production method of the cold rolled steel and utilize this the hot dipping steel sheet and the cold rolled steel which are used for the outside plate material and the like of the automobile.SolutionsAs for this invention in the high intensity cold rolled steel which is superior in the printing hardenability, normal temperature resistance aging characteristic and resistance secondary process brittleness and offering its production method, there is the purpose. This invention very small amount adds Ti, adds Al and Mo simultaneously, size of the crystal grain of after the annealing above ASTM No.9, the printing hardening quantity above 30MPa (BH) and designates the production method of the high intensity cold rolling steel sheet and utilize this the hot dipping steel sheet and the cold rolled steel which are superior in the printing hardenability which possesses the AI value below 30MPa as the effect by controlling the solid solution element in the steel appropriately in addition with control of production condition, with the method of making the size of the crystal grain refine after the annealing. According to this invention, the high intensity cold rolled steel and the hot dipping steel sheet which are superior in the printing hardenability, normal temperature resistance aging characteristic and resistance secondary process brittleness can be offered. Selective figure Figure 6