The invention discloses an automatic welding machine, a welding tool and a welding process, and belongs to the technical field of welding tools. The automatic welding machine comprises a base, whereina circular track is arranged on the base, a moving rod is arranged on the circular track, the moving rod is slidably connected to the circular track through rolling wheels, a circular ring disc is fixedly connected to the upper end of the moving rod, first locking plates are fixedly connected to the two sides of the lower end of the circular ring disc, a flange is placed on the circular ring disc, the upper end of the flange is provided with a circular pipe, and the two sides of the upper end of the flange are connected to second locking plates. According to the automatic welding machine, through arrangement of a nut and a first pressing plate, the circular pipe and the flange can be locked into a whole, and therefore when the circular pipe is rotated, the flange and the circular pipe canrotate at the same time, the situation that the flange and the circular pipe do not have relative displacement is avoided, and the welding quality is improved.