Abstract: An aspect of the present invention is a production method of a rolled sheet for cold-rolling, the method being characterized by including: a hot-rolling step for forming a rolled sheet by hot-rolling a pure titanium material while coiling; and an annealing step for annealing the hot-rolled sheet after the hot-rolling step, the coiling temperature in the hot-rolling step being 500° C. or less, and the annealing step being controlled so that the percentage area of recrystallized grains in the microstructure of the hot-rolled sheet after annealing is at least 90% and the mean grain size of the recrystallized grains is 5 ?m to 10 ?m.

Abstract: An aspect of the present invention is a production method of a rolled sheet for cold-rolling, the method being characterized by including: a hot-rolling step for forming a rolled sheet by hot-rolling a pure titanium material while coiling; and an annealing step for annealing the hot-rolled sheet after the hot-rolling step, the coiling temperature in the hot-rolling step being 500° C. or less, and the annealing step being controlled so that the percentage area of recrystallized grains in the microstructure of the hot-rolled sheet after annealing is at least 90% and the mean grain size of the recrystallized grains is 5 ?m to 10 ?m.

Abstract: Disclosed is a high-strength hot-rolled steel sheet containing C in a range of 0.03 to 0.15 mass %, Mn in a range of 0.5 to 2 mass %, and Al in a range of 0.01 to 0.1 mass %, respectively, while controlling S to not more than 0.02 mass % (0% included), wherein the metallic structure thereof has a polygonal ferrite as the main phase, and contains martensite as a second phase, further containing P in a range of 0.030 to 0.08 mass %, and Cr in a range of 0.3 to 1.00 mass %, respectively, while controlling Si to not more than 0.1 mass % (0% included). Thus, a high-strength hot-rolled steel sheet superior in workability, and fatigue property, and excellent in surface quality is provided at a relatively low cost.

Abstract: Disclosed is a high-strength hot-rolled steel sheet containing C in a range of 0.03 to 0.15 mass %, Mn in a range of 0.5 to 2 mass %, and Al in a range of 0.01 to 0.1 mass %, respectively, while controlling S to not more than 0.02 mass % (0% included), wherein the metallic structure thereof has a polygonal ferrite as the main phase, and contains martensite as a second phase, further containing P in a range of 0.030 to 0.08 mass %, and Cr in a range of 0.3 to 1.00 mass %, respectively, while controlling Si to not more than 0.1 mass % (0% included). Thus, a high-strength hot-rolled steel sheet superior in workability, and fatigue property, and excellent in surface quality is provided at a relatively low cost.