Welding method for extending special channel beams for railway double-decker transport vehicles with concave bottoms

The invention relates to a welding method for extending special channel beams for railway double-decker transport vehicles with concave bottoms. The welding method includes steps of 1), truncating to-be-welded channel steel; 2), forming a plurality of V-shaped grooves on a web plate and wing surfaces of each piece of to-be-welded channel steel; 3), completely cutting all the V-shaped grooves, then respectively removing adhering slag, scale cinders and oil rust and polishing the V-shaped grooves by grinding wheels one by one; 4), welding an arc starting plate on the wing surface on one side of a joint surface of each piece of to-be-welded channel steel, and welding an arc ending plate on the wing surface on the other side of the joint surface of each piece of to-be-welded channel steel; 5), performing positioned welding on four sections on the web plates and the wing surfaces of the corresponding joint surfaces of each two corresponding pieces of to-be-welded channel steel at intervals when the two corresponding pieces of channel steel are started to be abutted; 6), examining assembly and positioned welding seam quality and carrying out a step 7) to carry out welding after the assembly and positioned welding seam quality is qualified; 7), completing overturn welding on space among the wed plate and the two wing surface of the corresponding joint surface of each piece of to-be-welded channel steel according to a preset welding station sequence; 8), respectively cutting and removing the various arc starting plates and the arc ending plates by flame after welding on the integral to-be-welded channel steel is completed; 9), polishing ultrahigh portions, enabling joints to be in smooth transition and completing welding for extending the channel steel.