Welding device for large-diameter variable-thickness pipe and welding method thereof

The invention provides a welding device for a large-diameter variable-thickness pipe and a welding method thereof. The device comprises a telescopic magnetic rod assembly, extrusion rollers, an induction coil, a guide roller, a guide carrier roller, a speed measuring sensor, a thickness measuring sensor and a pipe blank. An opening angle is arranged at one end of the pipe blank, the extrusion rollers are arranged on the two sides of the starting point end of the opening angle of the pipe blank respectively, and the induction coil, the guide roller, the guide carrier roller, the speed measuring sensor, the thickness measuring sensor and the telescopic magnetic rod assembly are sequentially installed in the direction from the starting point end to the terminal point end of the opening angle. The method comprises the specific steps that firstly, initial parameters related to welding are input into a processor, then the opening angle of the pipe blank is adjusted in real time, then related parameters of a welding