Automatic welding method of loop-weld structured but joints

The invention discloses an automatic welding method of loop-weld structured but joints. The automatic welding method includes machining an edge before welding, positioning before welding and protectively preheating before welding; adjusting the position of a welding gun after assembly so as to enable the welding gun to be above a weld bead; self-melting, bottoming and welding; welding a cover surface; slowing down cooling and successively treating thermally and the like. The automatic welding method can realize bottoming and cover surface welding formation of the loop weld structure 4-12 mm in thickness, production efficiency is improved by 200-300%, and one-time welding success rate of products is greatly increased.