Abstract: A high-strength surface-coated steel sheet includes a base steel sheet having a composition by mass of C: 0.01 to 0.20%, Si: 0.01 to 0.50%, Mn: 0.10 to 2.50%, P: 0.005 to 0.050%, B: 0.0005 to 0.010%, Ti: 0.01 to 0.20%, Nb: 0 to 0.10%, Mo: 0 to 0.50%, Cr: 0 to 0.50%, Al: 0.01 to 0.10%, and the balance of Fe and inevitable impurities; and a Zn—Al—Mg-based coating layer disposed on a surface of the base steel sheet, The steel sheet has a diffusible hydrogen concentration in the base steel sheet of 0.30 ppm or less and having a time until occurrence of red rust of 7000 hours or more as measured by a salt spray test. The high-strength hot-dip Zn—Al—Mg-based-plated steel sheet has a significantly lowered in-steel concentration of hydrogen which has entered the steel in a plating line and exhibits excellent corrosion resistance.

Abstract: Provided is a plated steel sheet having both strength and workability. In a hot-dip Zn—Al—Mg-based plated steel sheet, the steel substrate contains C in an amount of 0.050 to 0.180% by mass, Si in an amount of 0.001 to 0.50% by mass, Mn in an amount of 1.00 to 2.80% by mass, Ti in an amount of 0.01 to 0.10% by mass, and B in an amount of 0.0005 to 0.0100% by mass, an average grain size of cementite after winding in a hot rolling step is not greater than 2 ?m, a metal structure after a continuous hot-dip galvanizing step includes a ferrite phase and not less than 15 and less than 45% by area of a second phase, and the second phase is composed of martensite or composed of martensite and bainite and has an average crystal grain size of not greater than 8 ?m.

Abstract: A high-strength surface-coated steel sheet includes a base steel sheet having a composition by mass of C: 0.01 to 0.20%, Si: 0.01 to 0.50%, Mn: 0.10 to 2.50%, P: 0.005 to 0.050%, B: 0.0005 to 0.010%, Ti: 0.01 to 0.20%, Nb: 0 to 0.10%, Mo: 0 to 0.50%, Cr: 0 to 0.50%, Al: 0.01 to 0.10%, and the balance of Fe and inevitable impurities; and a Zn—Al—Mg-based coating layer disposed on a surface of the base steel sheet, The steel sheet has a diffusible hydrogen concentration in the base steel sheet of 0.30 ppm or less and having a time until occurrence of red rust of 7000 hours or more as measured by a salt spray test. The high-strength hot-dip Zn—Al—Mg-based-plated steel sheet has a significantly lowered in-steel concentration of hydrogen which has entered the steel in a plating line and exhibits excellent corrosion resistance.

Abstract: A steel sheet hot-dip coated with a Zn—Al—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° to 15° 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.

Abstract: A steel sheet hot-dip coated with a Zn—Al—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° to 15° 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.