Welding device for rear axle flange plate and connecting pipe and welding method thereof

The invention provides a welding device for a rear axle flange plate and a connecting pipe. The welding device comprises a supporting plate and a welding gun, a vertical plate, a first supporting rotating disc and an air cylinder frame are fixed on the supporting plate, a rotating disc is provided with a first rotating shaft extending downwards, the first rotating shaft is rotationally connected with the first supporting rotating disc, and the first rotating shaft is connected with a first servo motor through a first coupler; the rotating disc is used for positioning and installing the flangeplate, the lower end of the connecting pipe is positioned and installed on the flange plate, a double-rod air cylinder is fixed on the air cylinder frame, and the piston rod of the double-rod air cylinder is fixedly connected with the welding gun; and the vertical plate is fixed to a lifting mechanism, lifting frame of the lifting mechanism is connected with the supporting rotating disc through anelastic mechanism, the co