Abstract: High strength plated steel sheet having high hydrogen embrittlement resistance, that is, alloyed hot dip galvannealed steel sheet including steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50% and a alloyed hot dip galvannealed layer deposited on at least one surface of the steel sheet to 10 to 100 g/m2 and containing Fe: 5.0 to 15.0% and Al: 0.01 to 1.0%, having an internal oxidation layer including grain boundary oxides in a surface layer of the steel sheet, when examining a cross-section of a surface layer of the steel sheet, a Ratio A of the length of the grain boundary oxides projected an interface of the steel sheet and the alloyed hot dip galvannealed layer to the length of interface is 50% or more and 100% or less, and a surface depleted layer with a steel composition not including the grain boundary oxides which satisfies, by mass %, Si?0.6% and Al?0.05% is included at a depth of ½ of the average depth of the internal oxidation layer.

Abstract: High strength steel sheet and plated steel sheet having high plateability, LME resistance, and hydrogen embrittlement resistance, that is, steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50%, having an internal oxidation layer including fine granular oxides in a surface layer of the steel sheet, a number density of fine granular oxides in the internal oxidation layer being 4.0/?m2 or more, and including a surface depleted layer with a steel composition not including oxides which satisfies, by mass %, Si?0.6% and Al?0.05% at a depth of ½ of the average depth of the internal oxidation layer calculated from the cross-sectional SEM image of the steel sheet, and a plated steel sheet using the same.

Abstract: High strength steel sheet and plated steel sheet having high plateability, LME resistance, and hydrogen embrittlement resistance, that is, steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50%, having an internal oxidation layer including fine granular oxides and coarse granular oxides in a surface layer of the steel sheet, a number density of fine granular oxides in the internal oxidation layer being 4.0/?m2 or more, a number density of coarse granular oxides in the internal oxidation layer being 4.0/25 ?m2 or more and 30.0/25 ?m2 or less, and including a surface depleted layer with a steel composition not including oxides which satisfies, by mass %, Si?0.6% and Al?0.05% at a depth of ½ of the average depth of the internal oxidation layer calculated from the cross-sectional SEM image of the steel sheet, and a plated steel sheet using the same.

Abstract: High strength steel sheet and plated steel sheet having high plateability, LME resistance, and hydrogen embrittlement resistance, that is, steel sheet containing C: 0.05 to 0.40%, Si: 0.2 to 3.0%, Mn: 0.1 to 5.0%, and sol. Al: 0.4 to 1.50%, having an internal oxidation layer including fine granular oxides, coarse granular oxides, and grain boundary oxides in a surface layer of the steel sheet, a number density of fine granular oxides in the internal oxidation layer being 4.0/?m2 or more, a number density of coarse granular oxides in the internal oxidation layer being 4.0/25 ?m2 or more, having a Ratio A of the length of the grain boundary oxides projected on the surface of the steel sheet to the length of the surface of the steel sheet when examining a cross-section of the surface layer of the steel sheet being 50% or more and 100% or less, and including a surface depleted layer with a steel composition not including oxides which satisfies, by mass %, Si?0.6% and Al?0.

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 high-strength plated steel plate for a welded structural member having a steel composition containing from 0.050 to 0.150% of C, from 0.001 to 1.00% of Si, from 1.00 to 2.50% of Mn, from 0.005 to 0.050% of P, from 0.001 to 0.020% of S, and from 0.005 to 0.100% of Al, having a steel base material having a metal structure containing a ferrite phase and a second phase containing mainly martensite having an average crystal grain diameter of 8 mm or less, and having a chemical composition and a thickness t (mm) of the steel base material regulated to obtain a value, C/0.2+Si/5.0+Mn/1.3+Cr/1.0+Mo/1.2+0.4t?0.7(Cr+Mo)1/2, of 2.9 or less. The high-strength plated steel plate is excellent in corrosion resistance of the welded portion, resistance to liquid metal embrittlement cracking, and bending workability.

Abstract: A high-strength plated steel plate for a welded structural member having a steel composition containing from 0.050 to 0.150% of C, from 0.001 to 1.00% of Si, from 1.00 to 2.50% of Mn, from 0.005 to 0.050% of P, from 0.001 to 0.020% of S, and from 0.005 to 0.100% of Al, having a steel base material having a metal structure containing a ferrite phase and a second phase containing mainly martensite having an average crystal grain diameter of 8 mm or less, and having a chemical composition and a thickness t (mm) of the steel base material regulated to obtain a value, C/0.2+Si/5.0+Mn/1.3+Cr/1.0+Mo/1.2+0.4t?0.7(Cr+Mo)1/2, of 2.9 or less. The high-strength plated steel plate is excellent in corrosion resistance of the welded portion, resistance to liquid metal embrittlement cracking, and bending workability.

Abstract: [Problem] To provide a steel sheet hot-dip-plated with a Zn—Al—Mg-based alloy coating, which is remarkably improved in point of all the burring workability, the liquid metal embrittlement cracking resistance and the corrosion resistance in the welded part thereof, as a steel material favorable for arc-welded structural members.

Abstract: [Problem] To produce a hot-dip Zn—Al—Mg alloy coated steel sheet that is excellent in coating adhesion, by using, as a base sheet for coating, a steel sheet that is imparted with resistance to liquid metal embrittlement cracking by adding B. [Solution] A hot-dip zinc alloy coated steel sheet excellent in coating adhesion containing at least one of a Si simple oxide, a Mn simple oxide, a Cr simple oxide, a Si—Mn composite oxide, a Si—Cr composite oxide, a Mn—Cr composite oxide, and a Si—Mn—Cr composite oxide in a portion within 10 ?m from an interface between a steel sheet as a base sheet for coating, and a hot-dip galvanized layer formed on a surface thereof.

Abstract: A method for producing a hot-dip zinc alloy coated steel sheet excellent in coating adhesion, comprising: hot-rolling a steel sheet, subjecting the base sheet for coating to a reduction heat treatment, and subjecting the base sheet for coating to hot-dip zinc alloy coating. The hot-dip alloy coated steel sheet is excellent in coating adhesion, by using, as a base sheet for coating, a steel sheet that is imparted with resistance to liquid metal embrittlement cracking by adding B. The hot-dip zinc alloy coated steel sheet excellent in coating adhesion contains at least one of a Si simple oxide, a Mn simple oxide, a Cr simple oxide, a Si—Mn composite oxide, a Si—Cr composite oxide, a Mn—Cr composite oxide, and a Si—Mn—Cr composite oxide in a portion within 10 ?m from an interface between a steel sheet as a base sheet and a hot-dip galvanized layer formed on a surface 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.

Abstract: A high-strength plated steel plate for a welded structural member having a steel composition containing from 0.050 to 0.150% of C, from 0.001 to 1.00% of Si, from 1.00 to 2.50% of Mn, from 0.005 to 0.050% of P, from 0.001 to 0.020% of S, and from 0.005 to 0.100% of Al, having a steel base material having a metal structure containing a ferrite phase and a second phase containing mainly martensite having an average crystal grain diameter of 8 mm or less, and having a chemical composition and a thickness t (mm) of the steel base material regulated to obtain a value, C/0.2+Si/5.0+Mn/1.3+Cr/1.0+Mo/1.2+0.4t?0.7(Cr+Mo)1/2, of 2.9 or less. The high-strength plated steel plate is excellent in corrosion resistance of the welded portion, resistance to liquid metal embrittlement cracking, and bending workability.

Abstract: [Problem] To produce a hot-dip Zn—Al—Mg alloy coated steel sheet that is excellent in coating adhesion, by using, as a base sheet for coating, a steel sheet that is imparted with resistance to liquid metal embrittlement cracking by adding B. [Solution] A hot-dip zinc alloy coated steel sheet excellent in coating adhesion containing at least one of a Si simple oxide, a Mn simple oxide, a Cr simple oxide, a Si—Mn composite oxide, a Si—Cr composite oxide, a Mn—Cr composite oxide, and a Si—Mn—Cr composite oxide in a portion within 10 ?m from an interface between a steel sheet as a base sheet for coating, and a hot-dip galvanized layer formed on a surface thereof.

Abstract: [Problem] To provide a steel sheet hot-dip-plated with a Zn—Al—Mg-based alloy coating, which is remarkably improved in point of all the burring workability, the liquid metal embrittlement cracking resistance and the corrosion resistance in the welded part thereof, as a steel material favorable for arc-welded structural members.