An electric resistance welded steel pipe or tube comprises: a base metal being a steel sheet having a specific chemical composition and an electric resistance weld portion having a bond width of 4010.sup.6 m or more and 12010.sup.6 m or less, wherein C.sub.0-C.sub.1 is 0.05 mass % or less, where C.sub.0-C.sub.1 is a difference between C.sub.1 in mass % which is a minimum C content of the electric resistance weld portion and Co in mass % which is a C content of the steel sheet, and a depth of a total decarburized layer in each of an inner surface layer and an outer surface layer of the electric resistance welded steel pipe or tube is 5010.sup.6 m or less.

An exemplary method of making a piston assembly may include providing a piston crown defining at least in part an upper combustion bowl surface. The piston crown includes at least one crown mating surface. The method further comprising moving the crown mating surface in proximity to a skirt mating surface defined by a piston skirt, wherein the crown and skirt cooperate to define a cooling gallery extending about a periphery of the crown. The method may further include bonding the crown and skirt together by initiating an electric current along a conductive path between the crown and skirt mating surfaces, the conductive path comprising at least one conductive material extending from the crown mating surface to the skirt mating surface.

An exemplary method of making a piston assembly may include providing a piston crown defining at least in part an upper combustion bowl surface. The piston crown includes at least one crown mating surface. The method further comprising moving the crown mating surface in proximity to a skirt mating surface defined by a piston skirt, wherein the crown and skirt cooperate to define a cooling gallery extending about a periphery of the crown. The method may further include bonding the crown and skirt together by initiating an electric current along a conductive path between the crown and skirt mating surfaces, the conductive path comprising at least one conductive material extending from the crown mating surface to the skirt mating surface.

A side impact protective structure is provided for a vehicle floor pan. Right and left rear rails are attached, respectively, to right and left lateral sides of the floor pan. A kick-up cross member extends transversely between the right and left rocker assemblies. A right reinforcement is welded to the floor pan, the right rear rail, and the kick-up cross member. A left reinforcement is welded to the left rear rail, to the floor pan and the kick-up cross member. An assembly method includes the steps of selecting a thin mild steel floor pan between a thicker HSLA steel structural member and a thicker corner reinforcement and welding the components together with three thickness welds.

A side impact protective structure is provided for a vehicle floor pan. Right and left rear rails are attached, respectively, to right and left lateral sides of the floor pan. A kick-up cross member extends transversely between the right and left rocker assemblies. A right reinforcement is welded to the floor pan, the right rear rail, and the kick-up cross member. A left reinforcement is welded to the left rear rail, to the floor pan and the kick-up cross member. An assembly method includes the steps of selecting a thin mild steel floor pan between a thicker HSLA steel structural member and a thicker corner reinforcement and welding the components together with three thickness welds.

A high strength electric resistance welded steel pipe has a yield strength of 450 MPa or more and excellent resistance to softening for a long period in an intermediate temperature range and a method of manufacturing the steel pipe are provided. The steel pipe has a chemical composition containing, by mass%, C: 0.026% or more and 0.084% or less, Si: 0.10% or more and 0.30% or less, Mn: 0.70% or more and 1.90% or less, Al: 0.01% or more and 0.10% or less, Nb: 0.001% or more and 0.070% or less, V: 0.001% or more and 0.065% or less, Ti: 0.001% or more and 0.033% or less, Ca: 0.0001% or more and 0.0035% or less, in which the condition that Pcm is 0.20 or less is satisfied.

An electric resistance welded pipe or tube comprises a weld portion in a pipe or tube longitudinal direction, wherein a maximum value of a wall thickness distribution of the weld portion is less than or equal to 1.05 times an average wall thickness of the electric resistance welded pipe or tube, a width of a weld metal in the weld portion in a circumferential direction is 1 m or more and 800 m or less over an entire thickness of the electric resistance welded pipe or tube, and a ratio of a maximum value to a minimum value (=maximum value/minimum value) of the width of the weld metal is 1.0 or more and 2.5 or less.

A method for the production of a zigzag-shaped protection element formed from multiple individual profiles includes the following steps: providing the individual profiles, welding the individual profiles to form a zigzag-shaped preform of the protection element such as to form at least one weld seam, wherein the individual profiles are welded to each another at an angle of 30 to 120, inserting the preform into a hot molding tool, molding the preform into the zigzag-shaped protection element in the hot molding tool, and mold hardening of the zigzag-shaped protection element in the hot molding tool.

A method for the production of a zigzag-shaped protection element formed from multiple individual profiles includes the following steps: providing the individual profiles, welding the individual profiles to form a zigzag-shaped preform of the protection element such as to form at least one weld seam, wherein the individual profiles are welded to each another at an angle of 30 to 120, inserting the preform into a hot molding tool, molding the preform into the zigzag-shaped protection element in the hot molding tool, and mold hardening of the zigzag-shaped protection element in the hot molding tool.

A method for monitoring welding of an electric resistance welded steel pipe of the present invention includes: an image acquisition step in which, when an electric resistance welded steel pipe is welded, a V-convergence portion including an edge detection area and a V-convergence point, and a welding portion including a position where a molten steel starts to be discharged from an inside of a wall thickness and a bead, are imaged to obtain a captured image; a determination information acquisition step in which the captured image is image-processed, and a molten length from the V-convergence point to the position where the molten steel starts to be discharged or a molten width of the welding portion or a combination thereof is acquired as a determination information; and a determining step in which it is determined whether a cold welding has occurred by comparing the determination information with a determination threshold value set in advance for each wall thickness of the electric resistance welded steel pipe.