Abstract: A hot-rolled steel sheet has a chemical composition that contains, in mass %, C, Si, Mn, P, S, Al, N and Ti, and that satisfies Formula (1); and a microstructure containing bainite and ferrite. In the interior of the steel sheet an average value of pole densities of an orientation group {100}<011> to {223}<110> is 4 or less, and a pole density of a {332}<113> crystal orientation is 4.8 or less. In an outer layer of the steel sheet, a pole density of a {110}<001> crystal orientation is 2.5 or more. Furthermore, among Ti carbo-nitrides in the steel sheet, the number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is 1.0×1017 per cm3 or less, and a bake hardening amount is 15 MPa or more.

Abstract: A hot-rolled steel sheet for a tailored rolled blank is provided that has high tensile strength and is excellent in cold formability. The hot-rolled steel sheet has: a chemical composition that contains, in mass %, C, Si, Mn, P, S, Al, N and Ti, with the balance being Fe and impurities, and that satisfies Formula (1); and a microstructure containing, in terms of area ratio, 20% or more of bainite, wherein 50% or more in terms of area ratio of the balance is ferrite. In the interior of the hot-rolled steel sheet an average value of pole densities of an orientation group {100}<011> to {223}<110> is 4 or less, and a pole density of a {332}<113> crystal orientation is 4.8 or less. In an outer layer of the hot-rolled steel sheet, a pole density of a {110}<001> crystal orientation is 2.5 or more. Furthermore, among Ti carbo-nitrides in the hot-rolled steel sheet, the number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is 1.

Abstract: A tailored rolled blank in which a plate thickness changes in a tapered shape in a rolling direction, comprises a thick-wall portion, and a thin-wall portion that is thinner than the thick-wall portion. In the tailored rolled blank, a ratio of an average hardness Htmax of a thickest wall portion at which the plate thickness is thickest to an average hardness Htmin of a thinnest wall portion at which the plate thickness is thinnest is in a range of more than 1.0 to 1.5. For the tailored rolled blank, an average dislocation density of the thinnest wall portion is 1×1014 m?2 or less, and a number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is more than 2×1017 per cm3.

Abstract: A heat-rolled steel plate has a chemical composition that contains, in mass %, C, Si, Mn, P, S, Al, N and Ti, and that satisfies Formula (1); and a microstructure containing bainite and ferrite. In the interior of the steel plate an average value of pole densities of an orientation group {100}<011> to {223}<110> is 4 or less, and a pole density of a {332}<113> crystal orientation is 4.8 or less. In an outer layer of the steel plate, a pole density of a {110}<001> crystal orientation is 2.5 or more. Furthermore, among Ti carbo-nitrides in the steel plate, the number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is 1.0×1017 per cm3 or less, and a bake hardening amount is 15 MPa or more.

Abstract: A heat-rolled steel plate has a chemical composition that contains, in mass %, C, Si, Mn, P, S, Al, N and Ti, and that satisfies Formula (1); and a microstructure containing bainite and ferrite. In the interior of the steel plate an average value of pole densities of an orientation group {100}<011> to {223}<110> is 4 or less, and a pole density of a {332}<113> crystal orientation is 4.8 or less. In an outer layer of the steel plate, a pole density of a {110}<001> crystal orientation is 2.5 or more. Furthermore, among Ti carbo-nitrides in the steel plate, the number density of fine Ti carbo-nitrides having a particle diameter of 10 nm or less is 1.0×1017 per cm3 or less, and a bake hardening amount is 15 MPa or more.

Abstract: The welding quality classification apparatus relating to the present invention is an apparatus, wherein a data point indicating feature information of a welded joint to be classified whose welding quality is unknown is mapped to a point in a mapping space which has a dimensional number higher than the number of the features constituting the feature information, and the welding quality of a welded joint to be classified is classified based on which of regions of two welding qualities, which are formed by separating the mapping space with a decision boundary, contains the mapped point, and wherein a discriminant function is determined by adopting a weight which minimizes the sum of the classification error corresponding to classification accuracy of a training dataset and a regularization term having a positive correlation with the dimensional number of the discriminant function as weight for each feature constituting the discriminant function indicating the decision boundary.

Abstract: A butt welding apparatus and a butt welding method where end faces of at least one plate member to be welded are butted to each other to form a butt portion, and butt welding can be performed on respective plate members which have various thickness sizes on both side portions of the butt portion with electric resistance heat by a pair of electrode members which are common to the respective plate members. At least one electrode member (1) is provided on an outer face thereof with a convex portion (1A) which gradually retreats from one plate member (31) of two plate members (31, 32) as it extends from an intermediate portion, in a thickness direction, of the one electrode member (1) along the one plate member (31).

Abstract: A butt welding apparatus, a butt welding method, and a product manufactured by the butt welding method involves two electrode rollers disposed on both the front and back sides of a thick sheet member and a thin sheet member whose end surfaces are butted. The electrode rollers bridge across the sheet members and are composed of small diameter portions on the side of the thick sheet member and large diameter portions on the side of the thin sheet member. The small diameter portions come into contact with and press the thick sheet member before the large diameter portions come into contact with the thin sheet member. Thus, the end surface of the thick sheet member swells and deforms toward the thin sheet member and reliably comes into contact with the end surface of the thin sheet member, and power is applied between the end surfaces, even if not polished.

Abstract: The present invention is a butt welding apparatus and a butt welding method where end faces of at least one plate member to be welded are butted to each other to form a butt portion, and butt welding can be performed on respective plate members to be welded which have various thickness sizes on both side portions of the butt portion with electric resistance heat by a pair of two electrode members which are made common to the respective plate members and are supplied with power. At least one electrode member (1) of a pair of electrode members (1, 2) for butt-welding two plate members (31, 32) is provided on an outer face thereof with a retreating-shaped portion (1A) which gradually retreats from one plate member (31) of the two plate members (31, 32) according to extension from an intermediate portion, in a thickness direction, of the one electrode member (1) along the one plate member (31).

Abstract: Disclosed are a butt welding apparatus, a butt welding method, and a product manufactured by the butt welding method. Two electrode rollers (3, 4) are disposed on both the front and back sides of a thick sheet member (1) and on both the front and back sides of a thin sheet member (2) whose end surfaces (1A, 2A) are butted. The electrode rollers (3, 4) are applied with power, melt the butt portion (6) of the sheet members (1, 2) with electric resistance heat, and joint the butt portion. Further, the electrode rollers (3, 4) have a length bridging across the sheet members (1, 2) and are composed of first portions (3A, 4A) arranged as small diameter portions on the side of the thick sheet member (1) and second portions (3B, 4B) arranged as large diameter portions on the side of the thin sheet member (2). The first portions (3A, 4A) come into contact with the thick sheet member (1) and presses it before the second portions (3B, 4B) come into contact with the thin sheet member (2).

Abstract: Disclosed are a butt welding apparatus, a butt welding method, and a product manufactured by the butt welding method. Two electrode rollers (3, 4) are disposed on both the front and back sides of a thick sheet member (1) and on both the front and back sides of a thin sheet member (2) whose end surfaces (1A, 2A) are butted. The electrode rollers (3, 4) are applied with power, melt the butt portion (6) of the sheet members (1, 2) with electric resistance heat, and joint the butt portion. Further, the electrode rollers (3, 4) have a length bridging across the sheet members (1, 2) and are composed of first portions (3A, 4A) arranged as small diameter portions on the side of the thick sheet member (1) and second portions (3B, 4B) arranged as large diameter portions on the side of the thin sheet member (2). The first portions (3A, 4A) come into contact with the thick sheet member (1) and presses it before the second portions (3B, 4B) come into contact with the thin sheet member (2).

Abstract: A coating composition comprising 38%-66% of a binder resin (including a curing agent), 0.2%-6% of an organic lubricant, 20%-50% of an iron phosphide-based electrically conductive pigment, and 3%-25% of one or more other inorganic pigments including anticorrosive pigments (the total content of these pigments being between 31% and 56%), wherein the content of the binder resin (including a curing agent) (R) and that of the organic lubricant (W) satisfy the following inequality:-0.4R+16.2.ltoreq.W.ltoreq.-0.4R+30.4, andwherein the coating composition further comprises a curing catalyst in an amount of from 0.7% to 10% based on the solids of the binder resin (including a curing agent). The coating composition can be applied to a plated metal sheet having a zinc- or aluminum-based plated coating after the plated metal sheet has been subjected to chemical conversion treatment such as chromating treatment, to form a resinous coating thereon having a thickness of 2-9 .mu.

Abstract: A zinc or zinc alloy electroplated metal sheet comprises a metal sheet having, on at least one surface thereof, a composite zinc or zinc alloy plated coating formed by electroplating with zinc or a zinc alloy in a plating solution which contains at least one organic compound selected from the group consisting of alkynes, alkynols, amines and salts thereof, thio compounds, heterocyclic compounds, and aromatic carboxylic acids and salts thereof. The composite plated coating has a coating weight of 0.5-200 g/m.sup.2 and contains 0.001-10 wt % of co-deposited carbon. The electroplated metal sheet has improved post-painting corrosion resistance, press formability, and spot weldability.

Abstract: A multilayer plated aluminum sheet suitable for use in automobile body panels comprises a base aluminum sheet made of aluminum or an aluminum alloy and has a first layer of zinc or a zinc alloy formed by displacement plating on the surface of the aluminum sheet and one or more layers of electroplated coating formed on the first layer by electroplating in an acidic bath. Preferably, the upper electroplated coating comprises at least one layer of zinc or a zinc alloy and the uppermost layer of the coating is formed from a metallic material having a melting point above 500.degree. C.

Abstract: A precoated steel sheet having improved corrosion resistance and formability is disclosed, which comprises a Zn- or Zn alloy-plated steel sheet having on the plated surface either a colloidal silica-containing chromate undercoat layer and a polyhydroxypolyether resin-based topcoat of 0.3 to 10 .mu.m in thickness in which resin is derived by polycondensation of a dihydric phenol component selected from a mononuclear dihydric phenol, dinuclear dihydric phenol, and a mixture of both, with an epihalohydrin or a non-colloidal material-containing chromate underlayer and an epoxy resin based topcoat containing colloidal silica of a thickness of from 0.3-1.6 .mu.m in thickness. In spite of the absence of zinc powder, the precoated steel sheet can be satisfactorily welded by resistance welding when the thickness of the topcoat layer is not greater than 2.5 .mu.m, and even with such a thin topcoat, the precoated steel sheet retains its improved corrosion resistance and formability.