Double - gun tungsten arc welding of stainless steel tanks
There is a stainless steel storage tank material of 316(equivalent to our standard brand number 06 Cr17Ni12Mo2), plate thickness 4 mm, total body height of 11248 mm, outer diameter of 5000 mm, field assembly. Using tungsten arc welding, high temperature oxidation occurs during welding, too large assembly gap will also appear welding nodule difficult to remove; especially field assembly, can not use the process device, resulting in large deformation after welding, affecting the production efficiency and product quality. To this end, double gun mutual protection tungsten arc welding can overcome the above shortcomings. Double gun mutual protection tungsten arc welding means that two welders operate on both sides of the weld at the same time, carry on the vertical welding or cross welding position to weld, so that the welding pool is always in the air protection, and the weld seam is formed once through. It not only ensures the welding quality of the product, but also improves the production efficiency. The specific process of this method is as follows :1, assembly process 1) clean the welding surface of the qualified circular arc plate after rolling. After grinding by grinding wheel, clean it with acetone, do not open the groove in I-shaped splicing, and place the welding place in the position of vertical welding or transverse welding. 2) group pair, to ensure that the weld group pair clearance is 0~1.0, from one end with a single gun every about 100 mm on the inside with positioning weld fixed. welding current of 60 A, positioning weld should be as short as possible. 3) hammering the solder joint to eliminate the group at the wrong edges or protrusions. 4) gap between the two positions is about 15~20 mm.. Second, when the operation process adopts double gun mutual protection argon arc welding, the outside welder is the lead welding, and the left welding method is adopted, so as to observe the shape and position of the molten pool and be responsible for filling the welding wire; the inner welder adopts the right welding method, and does not fill the wire (or less fill the wire) for tracking welding. At the beginning of the arc, the outside welder observed the situation of the molten pool, and when the melting pool was better into melting round and the arc was blue red, it indicated that the position of the inner welding gun was correct and the heat input was appropriate, the welding wire could be filled. Welding attention to keep the inside and outside two guns relative position correct, general dislocation ≤5 mm.. The specific operation steps are as follows :1) adopt high frequency arc, wait for the arc to be stable, after the melting pool is round, start to move the welding torch, carry on the welding. When 2) stand welding, the welding torch front inclination angle is 70°~85°, when holding the welding torch in the right hand, fill the fuse pool in the upper left direction; when transverse welding, in addition to maintaining the forward inclination angle of 70°~85° in the horizontal direction, it should be tilted up for 15°. 3) the welding process, we pay close attention to the relationship between welding speed and weld fusion state, always keep the front end of molten pool moving welding in round state, the two welding guns should be uniform when moving, pay attention to the special color held by the arc when the internal and external welding torch corresponds. 4) welding torch nozzle to the welding piece distance to maintain 8-10 mm, when moving to maintain a certain height, so that the protective gas always cover the welding pool welding, so as not to oxidize. 5) the middle of the welding needs to stop, tap the cylinder wall to inform the other party. Third, the selection of welding parameters using DC positive polarity power supply for welding. Welding wire HO6Cr19Ni12Mo, wire diameter 1.6 mm; tungsten electrode diameter 3 mm; protection argon flow 8~11/ min; nozzle diameter 10, tungsten electrode nozzle length 5 7.
