Why should argon arc welding be used for the bottom of thick plate and steel structure?

Argon arc welding and argon arc welding bottom in the process of no difference, argon arc welding is suitable for thin-wall small pipe diameter (generally DN60 and below, wall thickness of 4mm) below, to ensure the quality of the weld root appearance formed. When the pipe diameter is large and the wall thickness is thick, argon arc welding should be used for the bottom manual welding cover surface. The purpose of manual welding cover surface is to ensure the appearance quality of large pipe diameter, and the work efficiency is higher than argon arc welding, and the cost is lower than argon arc welding. In the welding of water-cooled wall, superheater and economizer of boiler, the joint quality is excellent, and the grade of weld is above grade ⅱ by radiographic inspection. Argon arc welding bottom advantages (1) good quality As long as appropriate welding wire, welding process parameters and good gas protection can make the root of good penetration, uniform penetration, smooth surface, neat. There are no defects such as welding tumor, incomplete penetration, depression, porosity and slag inclusion which are easy to occur in general electrode arc welding. (2) high efficiency In the first layer of pipeline welding, manual argon arc welding is continuous arc welding. Therefore, manual argon arc welding can improve the efficiency by 2~4 times. Because argon arc welding does not produce welding slag, so there is no need to clean slag and repair weld bead, the speed is faster. In the second layer of arc welding cover surface, smooth and tidy argon arc welding bottom layer is very conducive to arc welding cover surface, can ensure good fusion between layers, especially in the welding of small diameter tube, the efficiency is more significant. (3) easy to master Manual arc welding root weld welding, must be experienced and high technical level of welders. Using manual argon arc welding base, generally engaged in welding workers after a short time of practice, basically can master. (4) the deformation is small Argon arc welding bottom heat affected zone is much smaller, so the welding joint deformation is small, residual stress is also small. Technological introduction (1) Welding example No. 20 steel is used for economizer, evaporation section tube bundle, water wall and low temperature superheater, and 12Cr1MoV is used for high temperature superheater tube. (2) Preparation before welding Before welding, the pipe mouth should be beveled at 30°, and the inner and outer pipe ends should be polished to metal color within the range of 15mm. Pipe counterpart clearance is 1~3mm. When the actual gap is too large, the transition layer should be surfacing on one side of the pipe groove first. Set up temporary wind shelter facilities, strictly control the wind speed at the welding operation, because the wind speed exceeds a certain range, it is easy to produce air holes. (3) operation Use manual TUNGSTEN argon arc welding machine, welding machine itself equipped with high frequency arc device, can use high frequency arc. Arc extinguishing is different from electrode arc welding. If arc extinguishing is too fast, it is easy to produce arc pit cracks. Therefore, the molten pool should be led to the edge or thicker base metal during operation, and then gradually reduce the molten pool to slowly extinguish arc, and finally close the protective gas. For no. 20 steel pipe with wall thickness of 3~4mm, the filling material can be TIGJ50 (for 12Cr1 MoV, 08CrMoV), the tungsten rod diameter is 2mm, the welding current is 75~100A, the arc voltage is 12~14V, the protective gas flow is 8~10L/min, and the power supply type is DC direct connection.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods