Automatic welding device for gantry of heavy machinery

The invention relates to the technical field of welding devices, in particular to a heavy machinery gantry automatic welding device which comprises a gantry frame, a welding robot installed at the upper end of the gantry frame and a control system installed on the gantry frame. The clamping device comprises sleeves installed on the two sides of the portal frame, the sleeves on the two sides are hollow, inserting rods are inserted into the ends, away from the portal frame, of the sleeves, telescopic air cylinders are arranged on the faces, away from the inserting rods, of the interiors of the sleeves, the output ends of the telescopic air cylinders are fixedly connected to the ends, inserted into the sleeves, of the inserting rods, and a fixing plate is arranged between the two inserting rods. The fixing plates are integrally connected with the two inserting rods, the driving motors are fixedly installed on the faces, away from each other, of the fixing plates of the two clamping devices, the output ends of th