Disclosed is a cold-rolled steel sheet having a chemical composition satisfying, in mass%, C:0.06-0.6%, Si: 0.1-2%, Al: 0.01-3%, Si + Al: 1-4%, Mn: 1-6% and Si/Mn ≤ 0.40. There are 10 or more Mn-Si complex oxides having an Mn/Si atomic ratio of not less than 0.5 and a length of 0.01-5 μm per 100 μm2 of the steel sheet surface, and not more than 10% of the steel sheet surface is covered by oxides mainly containing Si.

High-strength cold-rolled steel sheet excellent in coating adhesion, workability and hydrogen embrittlement resistance, and steel component for automobile

Provided are: a high-strength cold-rolled steel sheet having excellent ductility, stretch-flangeability and bendability; and a method for manufacturing the high-strength cold-rolled steel sheet. A high-strength cold-rolled steel sheet having the following chemical composition, in mass%: 0.12 to 0.22% of C; 0.8 to 1.8% of Si; 1.8 to 2.8% of Mn; 0.020% or less of P; 0.0040% or less of S; 0.005 to 0.08% of Al; 0.008% or less of N; 0.001 to 0.040% of Ti; 0.0001 to 0.0020% of B; and 0.0001 to 0.0020% of Ca; with the remainder made up by Fe and unavoidable impurities. The high-strength cold-rolled steel sheet has such a structure that the total area ratio of a ferrite phase and a bainite phase is 50 to 70%, the average crystal particle diameter of the ferrite phase and the bainite phase is 1 to 3 μm, the area ratio of a tempered martensite phase is 25 to 45%, the average crystal particle diameter of the tempered martensite phase is 1 to 3 μm, and the area ratio of a retained austenite phase is 2 to 10%.

High-strength cold-rolled steel sheet and method for manufacturing same

A high-strength hot-rolled steel sheet excellent in shape fixability having ferrite or bainite as the phase of the largest volume percentage, satisfying all of the following at least at 1/2 sheet thickness: a mean value of X-ray random intensity ratio in the orientation component group of {100} to {223} to X-ray random diffraction intensity ratio of at least 2.5; a mean value of X-ray random intensity ratio in the three crystal orientation components of {554} , {111} , and {111} to X-ray random diffraction intensity ratio of 3.5 or less; an X-ray intensity ratio to X-ray random diffraction intensity ratio at {100} of at least the X-ray random intensity to X-ray random diffraction intensity ratio at {211} ; and an X-ray random intensity ratio to X-ray random intensity ratio diffraction intensity ratio at {100} of at least 2.5, having at least one of an r-value of the rolling direction and an r-value of a direction perpendicular to the rolling direction of not more than 0.7, having an anisotropy DeltauEl of uniform elongation of not more than 4%, having an anisotropy DeltaLE1 of local elongation of at least 2%, and having an DeltauEl of not more than the DeltaLE1.

High-strength hot-rolled steel sheet excellent in shape fixability and method of producing the same

A galvanized steel sheet having (a) a dual phase microstructure with a martensite phase and a ferrite phase and (b) a composition containing by percent weight: carbon in a range from about 0.01% to about 0.18%; manganese in a range from about 0.2% to about 3%; silicon ≦ about 1.2%; aluminum in a range from about 0.01% to about 0.1%; one or both of chromium and nickel in a range from about 0.1% to about 3.5%; calcium in a range from about 0.0003% to about 0.01%; phosphorus ≦ about 0.01%; sulfur ≦ about 0.03%; nitrogen ≦ about 0.02%; molybdenum ≦ about 1%; copper ≦ about 0.8%; one or more of niobium, titanium, and vanadium ≦ about 1%; and boron ≦ about 0.006% by weight; and with the balance of the composition being iron and incidental ingredients. In one embodiment, the steel sheet is both galvanized and galvannealed.

High strength, hot dip coated, dual phase, steel sheet and method of manufacturing same

A steel sheet for forming having low-temperature heat treatment property, in which heat treatment is performed within a range of lower temperature than a conventional steel sheet in the event of hot press forming or post-heat treatment after cold forming, a method of manufacturing the same, and a method of manufacturing parts using the same. The steel sheet has a composition of, by weight, carbon (C): 0.15 to 0.35%, silicon (Si): 0.5% or less, manganese (Mn): 1.5 to 2.2%, phosphorus (P): 0.025% or less, sulfur (S): 0.01% or less, aluminum (Al): 0.01 to 0.05%, nitrogen (N): 50 to 200 ppm, titanium (Ti): 0.005 to 0.05%, tungsten (W): 0.005 to 0.1%, and boron (B): 1 to 50 ppm, wherein Ti/N: less than 3.4, where Ti/N is the atomic ratio of the corresponding elements, Ceq expressed by the following formula ranges from 0.48 to 0.58, and temperature Ar3 ranges from 670° C. to 725° C. Wherein Ceq C+Si/24+Mn/6+Ni/40+Cr/5+V/14 where C, Si, Mn, Ni, Cr and V indicate the contents (wt %) of the respective elements.

Steel sheet for hot press forming having low-temperature heat treatment property, method of manufacturing the same, method of manufacturing parts using the same, and parts manufactured by the same

The present invention provides a steel sheet excellent in workability, which may be used for components of an automobile or the like, and a method for producing the same. More specifically, according to one exemplary embodiment of the present invention, a steel sheet excellent in workability, including in mass, 0.08 to 0.25% C, 0.001 to 1.5% Si, 0.01 to 2.0% Mn, 0.001 to 0.06% P, at most 0.05% S, 0.001 to 0.007% N, 0.008 to 0.2% Al, at least 0.01% Fe. The steel sheet having an average r-value of at least 1.2, an r-value in the rolling direction of at least 1.3, an r-value in the direction of 45 degrees to the rolling direction of at least 0.9, and an r-value in the direction of a right angle to the rolling direction of at least 1.2.

Shinya Sakamoto

Papers

Steel plate exhibiting excellent workability and method for producing the same

Method to produce steel sheet excellent in workability

Steel plate and tube exhibiting excellent workability and method for producing the same

Steel sheet excellent in workability

Steel sheet excellent in workability and method for producing the same