Nippon Steel Corporation

Nisshin Steel Co., Ltd.

Nippon Steel Nisshin Co., Ltd.

Kentarou Hirata

Mamoru Saito

Masaharu Oka

Yukio Katagiri

Masaaki Uranaka

Masahito Sakaki

Tomoharu Shigetomi

Shinya Uesugi

A hot-rolled steel sheet which has excellent rigidity along with high strength, excellent workability, and excellent LME resistance is provided. A hot-rolled steel sheet of the present embodiment consists of, in mass %, C: 0.040 to 0.120%, Si: 0.01 to 0.60%, Mn: 0.50 to 1.50%, P: 0.025% or less, S: 0.010% or less, Al: 0.010 to 0.070%, N: 0.0070% or less, Ti: 0.055 to 0.200%, and B: 0.0010 to 0.0050%, with the balance being Fe and impurities. In the microstructure of the hot-rolled steel sheet, an area fraction of bainitic ferrite is 85% or more and the dislocation density is 8.0×10to 100.0×10/m. The average equivalent circular diameter of Ti carbides in the hot-rolled steel sheet is 10 nm or less, and the average equivalent circular diameter of grains of the bainitic ferrite is 15 μm or less.

Hot-rolled steel sheet, hot-dip coated steel sheet, and method for producing hot-rolled steel sheet

A steel sheet hot-dip coated with a Zn&#x2014;Al&#x2014;Mg-based system, wherein the steel sheet material has a predetermined chemical composition; a Ti/C equivalent ratio represented by Formula (1) described in the specification is 0.4 to 1.5; a bainitic ferrite single phase or a phase including a bainitic ferrite phase and a ferrite phase exists as a main phase; the area ratio of a hard second phase and cementite is 3% or less; the ratio of small-angle boundaries with a difference in crystal orientation of 2&#xb0; to 15&#xb0; is 30% to 75%; and Ti-containing carbides having an average particle size of 20 nm or less are dispersed and precipitated and a method of manufacturing thereof.

Steel sheet hot-dip-coated with Zn&#x2014;Al&#x2014;Mg-based system having excellent workability and method for manufacturing same

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Tokyo, Japan

Kentarou Hirata