There is no difference in technology between full-argon arc welding and argon arc welding primer. Full-argon arc welding is applicable to thin wall small pipe diameter (generally DN60 and below, and the wall thickness is 4mm). The purpose is to ensure the appearance of good quality at the root of welding seam.
When the pipe diameter is larger and the wall thickness is thicker, argon arc welding should be used as the background manual welding cover surface. The purpose of manual welding cover surface is to ensure the appearance quality and the efficiency is higher than that of argon arc welding and the cost is lower than that of argon arc welding.
Argon arc welding backing welding process in the boiler water wall, superheater, economizer, such as welding, the joint quality is good, the X-ray detector, level of weld are Ⅱ magnitude.
Argon arc welding primer advantage
(1) are of good quality
As long as the right welding wire, welding process parameters and good gas protection can make the root to get a good penetration, and the penetration is uniform, smooth and neat surface. There is no common welding electrode arc welding is prone to welding nodules, incomplete, sag, porosity and slag inclusion defects.
(2) high efficiency
In the first layer welding of pipeline, manual argon arc welding is continuous arc welding. The electrode arc welding is a broken arc welding, so manual argon arc welding can improve the efficiency by 2~4 times. Since argon arc welding does not produce slag, it is unnecessary to clean the slag and repair the weld bead, so the speed can be improved faster. In the second layer of arc welding cover surface, smooth and neat argon arc welding bottom layer is very good for arc welding cover surface and can ensure good fusion between layers, especially in the welding of small diameter pipe, the efficiency is more significant.
(3) easy to master
The welding of the root seam of manual arc welding shall be performed by experienced welders with high technical level. Manual argon arc welding primer is adopted. Generally, workers engaged in welding work can master it after a short time of practice.
(4) the deformation
The heat affected area is much smaller when tig welding is done, so the welding joint has less deformation and residual stress.
(1) welding example
The material used for economizer, tube bundle of evaporation section, water wall and low temperature superheater is 20 steel, while the high temperature superheater tube is 12Cr1MoV.
(2) preparation before welding
Before welding, pipe should be 30 ° groove, pipe inside and outside the scope of 15 mm should be polished metal color. The gap between pipes is 1~3mm. When the actual gap is too large, it is necessary to surfacing the transition layer on the side of the pipe groove. Set up temporary shelter facilities and strictly control the wind speed in the welding operation place. Because the wind speed exceeds a certain range, air holes are easily generated.
Manual argon tungsten arc welding machine is used. The welding machine itself is equipped with high frequency arc starting device. High frequency arc starting can be adopted. Arc extinguishing is different from arc welding of welding rods. If the arc extinguishing is too fast, it is easy to generate arc pit cracks. Therefore, the welding pool should be directed to the edge or thicker base material during operation, and then gradually reduce the arc extinguishing of the welding pool, and finally close the protective gas.
For no. 20 steel tube with a wall thickness of 3~4mm, the filling material can be TIGJ50 (for 12Cr1 MoV, 08CrMoV is available), tungsten electrode rod diameter is 2mm, welding current is 75~100A, arc voltage is 12~14V, protective gas flow is 8~10L/min, and the power supply is direct current.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