The material of economizer, evaporation section tube bundle, water wall and low-temperature superheater is 20 # steel, and the material of high-temperature superheater tube is12cr1mov; Before welding, the nozzle should be bevelled at 30 degrees, and the inside and outside of the pipe end should be polished within 15 mm; The butt joint clearance of the pipeline is 1mm-3mm. When the actual butt joint gap is too large, it is necessary to establish a transition layer on one side of the pipeline groove first. Set up temporary shelter facilities and strictly control the wind speed in the welding workplace, because the wind speed exceeds a certain range, which is easy to produce blowholes; Use the manual tungsten argon arc welding machine (WST3 15), which is equipped with high-frequency arc ignition device and can be used. Arc extinguishing is different from covered electrode arc welding. If the arc extinguishing is too fast, it is easy to produce arc pit cracks, so the molten pool should be led to the edge or.