Abstract: A method for spot-welding metallic materials includes: sandwiching the metallic materials with a pair of electrodes; a pre-heating step for pre-heating a region different from a given region which should be welded by applying electric power having a high frequency to the pair of electrodes; and a welding step for spot-welding a given region of the metallic materials by applying electric power for welding to the pair of electrodes. The heating time in the pre-heating step and that in the welding step are independently controlled.

Abstract: A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.

Abstract: A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.

Abstract: A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment 1 sandwiches metallic materials 9 with a pair of electrodes 4, 4, and heats different regions of the metallic materials 9 by energization, with the pair of electrodes 4, 4 maintained at the same position with respect to the metallic materials 9. The welding equipment includes a first heating means 6 connected to the pair of electrodes 4, 4 for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means 8 for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit 10 for independently controlling the first and the second heating means 6, 8.

Abstract: A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment 1 sandwiches metallic materials 9 with a pair of electrodes 4, 4, and heats different regions of the metallic materials 9 by energization, with the pair of electrodes 4, 4 maintained at the same position with respect to the metallic materials 9. The welding equipment includes a first heating means 6 connected to the pair of electrodes 4, 4 for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means 8 for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit 10 for independently controlling the first and the second heating means 6, 8.

Abstract: An automobile strength member, having a cross-sectional shape giving a high bending repulsion at the beginning of impact and able to reduce the production cost and lighten the weight and achieve a greater improvement in safety and a reduction of cost of an automobile, that is, an automobile strength member comprised of a rectangular steel tube with a square cross-section, simultaneously satisfying the following relations (1) to (3), and having a strength of at least 690 MPa in terms of tensile strength: R1?1.5t??(1) tR?1.1t??(2) R1?R2??(3) where, t: thickness of side (mm) tR: thickness of corner (mm) R1: outside corner R (mm) R2: inside corner R (mm) where both a maximum value and minimum value of hardness at a cross-section of the rectangular steel tube are in the range of within ±30% of the average value of the entire cross-section.

Abstract: An automobile strength member, having a cross-sectional shape giving a high bending repulsion at the beginning of impact and able to reduce the production cost and lighten the weight and achieve a greater improvement in safety and a reduction of cost of an automobile, that is, an automobile strength member comprised of a rectangular steel tube with a square cross-section, simultaneously satisfying the following relations (1) to (3), and having a strength of at least 690 MPa in terms of tensile strength: R1?5t ??(1) tR?1.1t ??(2) R1?R2 ??(3) where, t: thickness of side (mm) tR: thickness of corner (mm) R1: outside corner R (mm) R2: inside corner R (mm) where both a maximum value and minimum value of hardness at a cross-section of the rectangular steel tube are in the range of within ±30% of the average value of the entire cross-section.

Abstract: An aluminum-coated structural member includes an Al—Si—Fe alloy layer formed on a steel substrate layer. The alloy layer includes a softer region having a hardness smaller than or equal to a hardness of the steel substrate layer, extends from the surface of the steel substrate layer toward a surface of the alloy layer, over a depth range greater than or equal to 50% of a thickness of the alloy layer. The Al—Si—Fe alloy layer has an oxide weight smaller than or equal to 500 mg/dm2.

Abstract: An aluminum-coated structural member includes an Al—Si—Fe alloy layer formed on a steel substrate layer. The alloy layer includes a softer region having a hardness smaller than or equal to a hardness of the steel substrate layer, extends from the surface of the steel substrate layer toward a surface of the alloy layer, over a depth range greater than or equal to 50% of a thickness of the alloy layer. The Al—Si—Fe alloy layer has an oxide weight smaller than or equal to 500 mg/dm2.