Patent ID: 8552332

Claim:
A bolt for being projection welded to a sheet part, the bolt comprising: a shaft part having a male screw; a circular enlarged diameter part formed integrally with the shaft part, the enlarged diameter part having a diameter larger than that of the shaft part and having an outer peripheral portion at an outermost periphery in a radial direction of the bolt; a circular fusion bonding projection including (i) an initial fusion part having at an end surface thereof a tapered portion with an inclination angle, the tapered portion being configured such that the initial fusion part is reduced in height toward an outer periphery thereof, and (ii) a main fusion part continuous with the initial fusion part; a plastic deformation portion disposed on an end surface of the enlarged diameter part and having an inclined surface which connects the outer peripheral portion of the enlarged diameter part with a base portion of the fusion bonding projection, the inclined surface being configured such that the plastic deformation portion is reduced in height toward an outer periphery thereof, wherein the fusion bonding projection is disposed at a center of the enlarged diameter part on a side opposite to the shaft part, wherein the bolt is configured to be projection welded by energizing only the fusion bonding projection with welding current for fusing the fusion bonding projection, wherein the bolt is configured such that pressurizing the fusion bonding projection against the sheet part and energizing the fusion bonding projection fusion-bonds the fusion bonding projection to the sheet part and brings an end surface of the enlarged diameter part on the outer peripheral side thereof into junction with a surface of the sheet part, and wherein the plastic deformation portion includes a central circular fusion part having a thickness corresponding to an inclination angle of the inclined surface, and an annular softening portion gradually reduced in thickness from the base portion toward the outer peripheral portion.