Abstract: A ring-shaped connecting portion is formed on a seat surface side of a pipe connector. The connecting portion is tapered so that thickness thereof gradually reduces toward a tip end thereof. A protrusion is formed on the tip end of the connecting portion. A ring-shaped groove is formed on a flat outer peripheral surface of a common rail. By fitting the protrusion into the groove, the connector can be positioned to a predetermined position of the common rail. In this structure, current can be concentrated to the protrusion and current density can be increased. As a result, sufficient bonding strength can be attained.

Abstract: A ring-shaped connecting portion is formed on a seat surface side of a pipe connector. The connecting portion is tapered so that thickness thereof gradually reduces toward a tip end thereof. A protrusion is formed on the tip end of the connecting portion. A ring-shaped groove is formed on a flat outer peripheral surface of a common rail. By fitting the protrusion into the groove, the connector can be positioned to a predetermined position of the common rail. In this structure, current can be concentrated to the protrusion and current density can be increased. As a result, sufficient bonding strength can be attained.

Abstract: A resistance welding method preventing a bonded part raised once to a high temperature from being cooled to a martensite phase in texture when bonding carbon steel having a carbon content of at least that of medium carbon steel by resistance welding and as a result preventing a drop in toughness and embrittlement of the bonded part, cracking of the bonded part, and aging cracks, comprising running a current through a common rail unit and holder formed by carbon steel having a carbon content of 0.35 wt % to bond the clamped parts and controlling the current run through the common rail unit and holder and current carrying time to slowly cool the bonded part raised to a high temperature for annealing treatment, whereby the Vicker's hardness can be lowered to less than 600 HV and the majority of the texture of the bonded part can be made the medium stage phase.

Abstract: A method of welding a hollow member and an insert member to form a composite member including a hollow member and insertion member requiring a high dimensional accuracy in the end-to-end distance in the axial direction and requiring a reliable concentricity in the center axes of the hollow member and insertion member, including preparing a hollow member and insertion member, inserting the insertion member in the hollow member, providing spot welds at an overlap portion where the hollow member and insertion member overlap to correct the axial end-to-end distance of the hollow member and the insertion member, and providing a partial weld at an overlap portion where the hollow member and insertion member overlap to correct the concentricity of the hollow member and the insertion member.

Abstract: A method of welding a hollow member and an insert member to form a composite member including a hollow member and insertion member requiring a high dimensional accuracy in the end-to-end distance in the axial direction and requiring a reliable concentricity in the center axes of the hollow member and insertion member, including preparing a hollow member and insertion member, inserting the insertion member in the hollow member, providing spot welds at an overlap portion where the hollow member and insertion member overlap to correct the axial end-to-end distance of the hollow member and the insertion member, and providing a partial weld at an overlap portion where the hollow member and insertion member overlap to correct the concentricity of the hollow member and the insertion member.

Abstract: A first member and a second member have end portions overlapped and welded by irradiating a laser beam on an outer surface of a lap portion. A front end surface of a fused portion slants at an obtuse angle larger than 90° with respect to a naked outer surface of the second member. A dilution rate S=B/(A+B) is equal to or less than 45%, where “A” represents a cross-sectional area of the fused portion merging into the first member and “B” represents a cross-sectional area of the fused portion merging into the second member.

Abstract: A first member (11) and a second member (12) of metal materials of different kinds are overlapped one upon the other, and the surface of the first member (11) is irradiated with a laser beam to form a melt-solidified portion (2). The melt-solidified portion (2) has a nearly inverted triangular shape in cross section becoming gradually narrow toward the inside from the front surface side of the first member (11), and has a low-hardness layer (21) on the front surface side and a high-hardness layer (22) on the inside. The high-hardness layer (22) has a welded structure in which first layers (23) and second layers (24) having a hardness smaller than that of said first layers (23) are alternatingly laminated in the direction in which the welding proceeds.