It is used for automatic welding of circular welding seam in barrel and axis, such as transmission shah, axle, hydraulic RAM, puncher, position stem, pressure container, water tank, tube union, flange, muffler, air reservoir, air compressor, etc. Welder is pneumatic controlled and weldment is on the support rollers. The whloe course of auto-control welding: Compacted by tailstock cylinder--put welding gun in place--spin welding--resetting. The welding gun involves tilting mechanism, self lifting mechanism and micro-turning mechanism. The welding machine can make multi-circle welding, suiting welds with a variety of depth and width. Every lap electric current and voltage can be present, Arc starting and extinguishing electric current is controlled by program, which is interlocked. It is the preferred equipment in mechanical major for the safe operation, reliable quality, smoothly pretty seam and substantially increased work efficiency. Adapting weldor: Argon-arc welding, gas shielded welding, hidden arc welding, etc.