The invention discloses a novel transmission shaft and a
friction stir welding process thereof. The novel transmission shaft comprises an aluminum
alloy shaft fork (or a steel shaft fork) and an aluminum
alloy shaft
pipe, wherein the shaft fork and the shaft
pipe are connected in a
friction stir welding manner; and a lap step is arranged at the end, connected with the shaft
pipe, of the shaft fork, the part, near the lap step, of the excircle of the shaft fork is provided with a small tangential boss, and the shaft pipe is arranged on the lap step of the shaft fork in a sleeving mode. In orderto realize the
welding of the same type materials of the aluminum
alloy shaft fork and the aluminum alloy shaft pipe or the
welding of the different materials of the steel shaft fork and the aluminumalloy shaft pipe, the small boss for ending the
friction stir welding process is designed on the shaft fork, so that the
adverse effect, from friction stir
welding ending pin holes, on the welding quality of the transmission shaft is avoided. The novel aluminum alloy (or steel / aluminum) transmission shaft which is high in connection strength, high in coaxiality, stable in quality, and large in
diameter-to-thickness ratio and the friction stir
welding process thereof are suitable for the market requirements of vehicle lightening and cost reducing.