Abstract: Two workpieces are frictionally welded by a friction welding apparatus which comprises a fixing holder and a rotary holder. One of the workpieces are held by a fixing chuck provided on the fixing holder, while the other is held by a rotary chuck provided on the rotary holder. Pressing portions are formed on opposing surfaces of the chucks.

Abstract: A chemical conversion treatment solution for titanium or titanium alloy which comprises fluoride ions in a concentration of between about 5 to 40 g/l, a nitrate ion to fluoride ion weight ratio between about 0.005:1 to 0.2:1, a sulphate ion to fluoride ion weight ratio of between about 0.02:1 to 0.5:1 at least one metallic ion selected from the group consisting of Mg, Ca, Mn, Fe, Co, Ni, Zn and Mo in a weight ratio to fluoride ion between about 0.02:1 to 0.5:1, and at least one compound which is organochelate compound in a concentration of between about 0.1 to 2 g/l, a water-soluble organic high polymer in a concentration of between about 0.1 to 10 g/l, or a surfactant in a concentration of between about 0.01 to 3 g/l.