Main welding seam shifting device and welding method for polygonal thick plate workpiece

The invention discloses a main welding seam shifting device and a welding method for a polygonal thick plate workpiece. A drive rotary bracket and a driven rotary bracket are arranged in a spaced mode; two rollers are positioned on rollers of two pairs of roller brackets of the drive rotary bracket and the driven rotary bracket; when a polygonal thick plate workpiece is placed on two roller central shafts, a cross supporting rod is arranged in an inner cavity of the polygonal thick plate workpiece, and the end surface of the cross supporting rod abuts against the inner wall of the polygonal thick plate workpiece; and a plurality of supporting and fixing blocks are screwed to ends of screws, and are horizontally and perpendicularly arranged between the inner walls of the two rollers and theouter wall of the polygonal thick plate workpiece. According to the method disclosed by the invention, the two rollers sleeve the two ends of the polygonal thick plate workpiece, and the rollers aredriven by rollers of the d