Patent ID: 8454079

Claim:
A front side member having a body formed from a tubular steel body which has a closed cross section and which is constituted by a single member in the axial direction, said body having, from one end towards the other end in the axial direction, a front portion which extends in the fore and aft direction of a vehicle body, a sloping portion which is continuous with the front portion and which slopes downwards along a dash panel, and a rear portion which is continuous with the sloping portion and which extends along the bottom surface of a floor panel which is joined to the dash panel, characterized in that a portion of the front portion is a first unquenched portion which has not undergone quenching treatment and the remainder other than that portion is a first high frequency quenched portion which has undergone high frequency quenching, all of the sloping portion is a second high frequency quenched portion which has undergone high frequency quenching, and a portion of the rear portion is second unquenched portion which has not undergone quenching, and the remainder other than that portion is a third high frequency quenched portion which has undergone high frequency quenching.