Abstract: By superposing a plurality of steel sheets including a high tensile steel sheet and performing pulsation conduction by an inverter DC type spot welding power supply and controlling the conduction time of the current pulses, intervals of the current pulses, that is, conduction idle time, and weld current applied at the current pulses in a variable manner, the optimum weld conditions are obtained. For resistance spot welding of the hot stamped steel sheet, resistance spot welding with a minimum weld current of a second pulsation step higher than the maximum weld current at a first pulsation step is used to suppress the occurrence of outer spatter and inner spatter and secure a broad suitable current range even if using an inverter DC power supply.

Abstract: A resistance spot welding method including: a pulsation process of clamping a sheet assembly of two or more overlapped steel sheets including at least one high tensile steel sheet using a pair of welding electrodes that are connected to a spot welding power source employing an inverter direct current method, and performing plural repetitions of current passing and current pass stopping, while pressing the steel sheets with the welding electrodes; and a continuous current pass process in which, after the pulsation process, current is passed continuously for a longer period of time than a maximum current pass time of the pulsation process, while pressing the steel sheets with the welding electrodes.

Abstract: In a spot welded joint according to an aspect of the present invention, with respect to a rectangular planar region of 100 ?m×100 ?m which is perpendicular to a sheet surface of the plurality of the steel sheets and which centers around an inner point spaced away by 100 ?m in a direction parallel with the sheet surface from an edge of a nugget, in a case of measuring a P concentration at a pitch of 1 ?m to obtain measured values of the P concentration at 100×100 of measurement points, and in a case of repetitively calculating an average value of the measured values of the P concentration at 20 of the measurement points which are adjacent to each other and which are arranged in a row in the direction parallel with the sheet surface among the 100×100 of the measurement points while shifting each one point to obtain 81×100 of the average values, the number of the average values which are more than two times an average P concentration is 0 to 100.

Abstract: In an arc spot welded joint manufacturing method in which two steel sheets configured by high strength steel having a component carbon content of 0.07% by mass or greater are overlapped, and the sheets are lap welded together in a spot pattern. The method includes a first welding pass in which a second steel sheet on the lower side is melted up to a back face side, and first weld metal is formed including a first reinforcement portion, and a second welding pass in which a second weld metal including a second reinforcement portion is formed over the first weld metal, such that the heights of the first reinforcement portion or the second reinforcement portion is formed at t/5 or greater with respect to the sheet thickness t of the steel sheets, and the average weld bead diameter is formed at from 3t to 10t.

Abstract: When two high-strength steel sheets (1A, 1B) whose sheet thickness ratio={the sum of sheet thicknesses of the steel sheets}/{the sheet thickness of the thinner steel sheet (when they have the same thickness, the sheet thickness per one sheet)} is within a range of not less than 2 nor more than 5 and which both have tensile strength of not less than 780 MPa nor more than 1850 MPa are stacked to be subjected to resistance spot welding, a first welding step being pre-welding with a pressurizing force P1 kN and a welding current I1 kA and a second welding step being main welding with a pressurizing force P2 kN and a welding current I2 kA are performed, the pressurizing forces P1, P2 are set to a fixed pressurizing force P=P1=P2 all through the first welding step and the second welding step and are set within a range expressed by {0.5?P?3.

Abstract: Provided is an Al-plated steel sheet used for hot pressing that has excellent lubricity in hot state, corrosion resistance after paint coating, and spot weldability. An Al-plated steel sheet used for hot pressing includes: a steel sheet; an Al plating layer formed on one surface or both surfaces of the steel sheet; and a surface coating layer formed on the Al plating layer. The surface coating layer contains a zinc compound, and the zinc compound is deposited on the Al-plated steel sheet in an amount of equal to or greater than 0.3 g/m2 and equal to or less than 1.5 g/m2 as an amount of metallic zinc per one surface, and a zinc deposition amount in any continuous 1 mm2 region is 1.5 g/m2 or less.

Abstract: Provided is a spot welded joint (10) which includes at least one thin steel plate with a tensile strength of 750 MPa to 1850 MPa and a carbon equivalent Ceq of equal to or more than 0.22 mass % to 0.55 mass % and in which a nugget (3) is formed in an interface of the thin steel plates (1A, 1B). In a nugget outer layer zone, a microstructure consists of a dendrite structure in which an average value of arm intervals is equal to or less than 12 ?m, an average grain diameter of carbides contained in the microstructure is 5 nm to 100 nm, and a number density of carbides is equal to or more than 2×106/mm2.

Abstract: [Object] To provide an Al-plated steel sheet used for hot pressing that has excellent lubricity in hot state, corrosion resistance after paint coating, and spot weldability. [Solution] An Al-plated steel sheet used for hot pressing according to the present invention includes: a steel sheet; an Al plating layer formed on one surface or both surfaces of the steel sheet; and a surface coating layer formed on the Al plating layer. The surface coating layer contains a zinc compound, and the zinc compound is deposited on the Al-plated steel sheet in an amount of equal to or greater than 0.3 g/m2 and equal to or less than 1.5 g/m2 as an amount of metallic zinc per one surface, and a zinc deposition amount in any continuous 1 mm2 region is 1.5 g/m2 or less.

Abstract: By superposing a plurality of steel sheets including a high tensile steel sheet and performing pulsation conduction by an inverter DC type spot welding power supply and controlling the conduction time of the current pulses, intervals of the current pulses, that is, conduction idle time, and weld current applied at the current pulses in a variable manner, the optimum weld conditions are obtained. For resistance spot welding of the hot stamped steel sheet, resistance spot welding with a minimum weld current of a second pulsation step higher than the maximum weld current at a first pulsation step is used to suppress the occurrence of outer spatter and inner spatter and secure a broad suitable current range even if using an inverter DC power supply.

Abstract: In an arc spot welded joint manufacturing method in which two steel sheets configured by high strength steel having a component carbon content of 0.07% by mass or greater are overlapped, and the sheets are lap welded together in a spot pattern. The method includes a first welding pass in which a second steel sheet on the lower side is melted up to a back face side, and first weld metal is formed including a first reinforcement portion, and a second welding pass in which a second weld metal including a second reinforcement portion is formed over the first weld metal, such that the heights of the first reinforcement portion or the second reinforcement portion is formed at t/5 or greater with respect to the sheet thickness t of the steel sheets, and the average weld bead diameter is formed at from 3t to 10t.

Abstract: When two high-strength steel sheets (1A, 1B) whose sheet thickness ratio={the sum of sheet thicknesses of the steel sheets}/{the sheet thickness of the thinner steel sheet (when they have the same thickness, the sheet thickness per one sheet)} is within a range of not less than 2 nor more than 5 and which both have tensile strength of not less than 780 MPa nor more than 1850 MPa are stacked to be subjected to resistance spot welding, a first welding step being pre-welding with a pressurizing force P1 kN and a welding current I1 kA and a second welding step being main welding with a pressurizing force P2 kN and a welding current I2 kA are performed, the pressurizing forces P1, P2 are set to a fixed pressurizing force P=P1=P2 all through the first welding step and the second welding step and are set within a range expressed by {0.5?P?3.

Abstract: In a spot welded joint according to an aspect of the present invention, with respect to a rectangular planar region of 100 ?m×100 ?m which is perpendicular to a sheet surface of the plurality of the steel sheets and which centers around an inner point spaced away by 100 ?m in a direction parallel with the sheet surface from an edge of a nugget, in a case of measuring a P concentration at a pitch of 1 ?m to obtain measured values of the P concentration at 100×100 of measurement points, and in a case of repetitively calculating an average value of the measured values of the P concentration at 20 of the measurement points which are adjacent to each other and which are arranged in a row in the direction parallel with the sheet surface among the 100×100 of the measurement points while shifting each one point to obtain 81×100 of the average values, the number of the average values which are more than two times an average P concentration is 0 to 100.

Abstract: A structure (10) for a front section of a vehicle body in a vehicle body (1) comprising a front chamber (3) disposed on the forward side of a vehicle interior (2) is provided with the following: a pair of front side members (11), located within the front chamber, that extend in the longitudinal direction of the vehicle body; a pair of strut towers (16) disposed on either side in the width direction of the front chamber and within which front wheel suspensions are disposed; and reinforcement members (20) that link the top of each strut tower with the front side members that face the strut towers, and that extend between the strut towers and the front side members. This configuration allows a structure for a front section of a vehicle body to be provided that can efficiently improve the rigidity of the vehicle body of an automobile against torsion and against lateral bending, and that can efficiently reduce the weight of the vehicle body by means of thickness reduction using a high-strength steel plate.

Abstract: Provided is a spot welded joint (10) which includes at least one thin steel plate with a tensile strength of 750 MPa to 1850 MPa and a carbon equivalent Ceq of equal to or more than 0.22 mass % to 0.55 mass % and in which a nugget (3) is formed in an interface of the thin steel plates (1A, 1B). In a nugget outer layer zone, a microstructure consists of a dendrite structure in which an average value of arm intervals is equal to or less than 12 ?m, an average grain diameter of carbides contained in the microstructure is 5 nm to 100 nm, and a number density of carbides is equal to or more than 2×106/mm2.

Abstract: Provided is a spot welded joint (10) which includes at least one thin steel plate with a tensile strength of 750 MPa to 1850 MPa and a carbon equivalent Ceq of equal to or more than 0.22 mass % to 0.55 mass % and in which a nugget (3) is formed in an interface of the thin steel plates (1A, 1B). In a nugget outer layer zone, a microstructure consists of a dendrite structure in which an average value of arm intervals is equal to or less than 12 ?m, an average grain diameter of carbides contained in the microstructure is 5 nm to 100 nm, and a number density of carbides is equal to or more than 2×106/mm2.

Abstract: A structure (10) for a front section of a vehicle body in a vehicle body (1) comprising a front chamber (3) disposed on the forward side of a vehicle interior (2) is provided with the following: a pair of front side members (11), located within the front chamber, that extend in the longitudinal direction of the vehicle body; a pair of strut towers (16) disposed on either side in the width direction of the front chamber and within which front wheel suspensions are disposed; and reinforcement members (20) that link the top of each strut tower with the front side members that face the strut towers, and that extend between the strut towers and the front side members. This configuration allows a structure for a front section of a vehicle body to be provided that can efficiently improve the rigidity of the vehicle body of an automobile against torsion and against lateral bending, and that can efficiently reduce the weight of the vehicle body by means of thickness reduction using a high-strength steel plate.

Abstract: Provided is a spot welded joint (10) which includes at least one thin steel plate with a tensile strength of 750 MPa to 1850 MPa and a carbon equivalent Ceq of equal to or more than 0.22 mass % to 0.55 mass % and in which a nugget (3) is formed in an interface of the thin steel plates (1A, 1B). In a nugget outer layer zone, a microstructure consists of a dendrite structure in which an average value of arm intervals is equal to or less than 12 ?m, an average grain diameter of carbides contained in the microstructure is 5 nm to 100 nm, and a number density of carbides is equal to or more than 2×106/mm2.

Abstract: The present invention relates to a resistance welding method suitable for use in spot welding between a steel-base metal sheet, which has been plated for rust prevention purposes, and an aluminum-base metal sheet and aims to permit a current to flow at a high density across the plated steel sheet and the aluminum-clad steel sheet, thereby realizing high-quality welding.An aluminum-clad steel sheet comprised of a steel layer having projections and an aluminum layer is interposed between the plated steel sheet and the aluminum-base metal sheet to be welded to each other. An electrode is energized by a predetermined weld current from an alternating power supply. The current path is limited to the area of the projections, and metallic melt formed by melting of the plating is accommodated between the projections, preventing the current-carrying area from being increased.

Abstract: A method for forming a layer of a carbide or nitride of a metallic element or boron nitride on the surface of a ceramics article. A molten salt bath is prepared by heating and melting a bath agent composed of boron oxide and/or borate, and at least one metallic element selected from Group IVa, Va, VIa elements, etc. An article to be treated which is made of silicon nitride, silicon carbide or sialon is immersed in the salt bath. This method provides a ceramics product with a uniform surface layer having superior frictional and electrical properties.

Abstract: A method and a bath agent for forming a carbide or diffusion layer on the surface of an article to be treated by immersing the article in a molten salt bath. The salt bath comprises borax, at least one oxide of a surface layer forming element (SFE) selected from the group consisting of an oxide of a Va-Group element of the Periodic Table and an oxide of chromium, and aluminum. The amounts of the SFE-oxide and of aluminum to the whole amount of the bath are 9.5 to 21.5 wt% and 4 to 7.5 wt%, respectively. The treating method provides the extended life of the bath, the facilitation of washing off the bath agent adhered to the treated article, etc.