Abstract: A preform having edges overlapped and jointed, two outer members for forming outer surfaces of a hydroformed product, and reinforcement members for forming reinforcement ribs that divide a hollow cross section of the hydroformed product, including a joint formed by, when more than three sheet materials for forming the outer members and the reinforcement members are overlapped together, welding a first sheet material on a surface of the overlapped sheet materials to a second sheet material positioned inside the first sheet material, and a space disposed and aligned with a joint plane between the second sheet material and a third sheet material located inside the second sheet material during the welding process.

Abstract: A preform having edges overlapped and jointed, two outer members for forming outer surfaces of a hydroformed product, and reinforcement members for forming reinforcement ribs that divide a hollow cross section of the hydroformed product, including a joint formed by, when more than three sheet materials for forming the outer members and the reinforcement members are overlapped together, welding a first sheet material on a surface of the overlapped sheet materials to a second sheet material positioned inside the first sheet material, and a space disposed and aligned with a joint plane between the second sheet material and a third sheet material located inside the second sheet material during the welding process.

Abstract: A preform having edges overlapped and jointed, two outer members for forming outer surfaces of a hydroformed product, and reinforcement members for forming reinforcement ribs that divide a hollow cross section of the hydroformed product, including a joint formed by, when more than three sheet materials for forming the outer members and the reinforcement members are overlapped together, welding a first sheet material on a surface of the overlapped sheet materials to a second sheet material positioned inside the first sheet material, and a space disposed and aligned with a joint plane between the second sheet material and a third sheet material located inside the second sheet material during the welding process.

Abstract: A preform having edges overlapped and jointed, two outer members for forming outer surfaces of a hydroformed product, and reinforcement members for forming reinforcement ribs that divide a hollow cross section of the hydroformed product, including a joint formed by, when more than three sheet materials for forming the outer members and the reinforcement members are overlapped together, welding a first sheet material on a surface of the overlapped sheet materials to a second sheet material positioned inside the first sheet material, and a space disposed and aligned with a joint plane between the second sheet material and a third sheet material located inside the second sheet material during the welding process.

Abstract: A surface-treating method of of screw parts, which method consists of coating beforehand a liquid organic resin based coating composition capable of forming a film having a volume resistivity of 1014 &OHgr;·cm or more at normal temperature onto a thread of screw parts to be mounted onto an automobile body by welding prior to a coating step of the automobile body, followed by heating and drying.