Due to the different sizes of stainless steel pipe fittings, according to the unique welding of stainless steel pipe fittings, the heat input should be reduced as much as possible. Therefore, manual arc welding and argon arc welding are used. Arc welding cover. All argon arc welding is used for d≦Φ159 mm. The welding technology of stainless steel pipe fittings needs to meet the following conditions.
① The welding machine adopts DC reverse connection during manual arc welding, and DC positive connection during argon arc welding;
②Before welding, the oxide skin on the surface of the welding wire should be brushed off with a stainless steel wire brush, and washed with acetone; the welding rod should be dried at 200-250°C for 1 hour and used immediately;
③ Before welding, clean up the oil stains within 25 mm on both sides of the groove of the workpiece, and clean the 25 mm range on both sides of the groove with acetone;
④ For argon arc welding, the diameter of the nozzle is Φ2 mm, the tungsten pole is tungsten pole, and the specification is Φ2.5 mm;
⑤ When welding stainless steel with argon arc welding, the back must be filled with argon gas protection to ensure the back is formed. The method of partially filling argon in the pipeline is adopted, the flow rate is 5-14L/min, and the front argon flow rate is 12-13L/min.
The thickness of weld seam should be as thin as possible during rooting welding, and it should be well fused with the root. It should be in a gentle slope shape when the arc is closed. The arc must be ignited and extinguished in the groove, and the arc crater should be filled to prevent the arc crater from cracking.
Since the stainless steel pipe fittings are austenitic stainless steel pipes, in order to prevent carbide precipitation sensitization and intergranular corrosion, the interlayer temperature and post-weld cooling rate should be strictly controlled. Immediately water-cooled, while using segmented welding. This symmetrical and dispersed welding sequence can not only increase the cooling rate of the joint, but also reduce the welding stress.
