Patent ID: 8492004

Claim:
A friction joining structure comprising steel products, a friction-joining steel plate, and a fastening device, wherein said friction joining steel plate is inserted between said steel products which are mutually friction joined by a compressive force derived from said fastening device, the friction joining steel plate is provided on both faces with a plurality of projected streaks continuously formed in a mutually parallel or mutually concentric manner and also provided with at least one insertion hole for allowing the fastening device to be inserted, wherein the plurality of projected streaks is designed to be at least three times higher in Vickers hardness than a surface of the steel products, said surface being in contact with the projected streaks, a stress intensity ratio (σ/σ mb ) obtained by dividing a compressive stress (σ) acting on the steel products due to the compressive force of the fastening device by a tensile strength (σ mb ) of each of the steel products is set to be 0.5 or less, wherein the tensile strength (σ mb ) of each of the steel products is from 400 to 500 N/mm 2 , and wherein the compressive stress (σ) is obtained by dividing a compressive force (N) of the fastening device by a total length dimension (L) of the projected streaks on one face of the friction joining steel plate and a width dimension (B) of a recess formed on the steel products by the projected streaks when the projected streaks enter the surface of the steel products, wherein the width dimension (B) at which the projected streaks enter into the surface of the steel products is set to be about ⅓ of a space (S) between the projected streaks.