Due to the different sizes of stainless steel threaded pipe fittings, according to the unique welding of stainless steel threaded pipe fittings, the heat input is reduced as much as possible. Therefore, manual arc welding and argon arc welding are used. , Manual arc welding cover. All argon arc welding for d≦φ159 mm. The welding technical requirements for stainless steel threaded pipe fittings are as follows:
①When manual arc welding, the welding machine adopts DC reverse connection, and when argon arc welding adopts DC positive connection;
②Before welding, the welding wire should be brushed off with a stainless steel wire brush to remove the oxide scale on the surface, and washed with acetone; the welding rod should be dried at 200-250℃ for 1 hour, and used as needed;
③Before welding, clean up the oil stains within 25 mm on both sides of the groove of the workpiece, and wash the 25 mm on both sides of the groove with acetone;
④When argon arc welding, the nozzle diameter is φ2 mm, the tungsten electrode is a tungsten electrode, and the specification is φ2.5 mm;
⑤When welding stainless steel with argon arc welding, the back side must be filled with argon gas to protect the back surface. Using the method of partially filling argon in the pipeline, the flow rate is 5-14l/min, and the front argon flow rate is 12-13l/min.
The thickness of the weld seam should be as thin as possible during the bottom welding, and the fusion with the root should be excellent, and the arc should be in a gentle slope shape when the arc is closed. The arc must be ignited and extinguished in the groove, and the crater should be filled when the arc is extinguished to prevent the crater from cracking.
Because the stainless steel threaded 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, and the interlayer temperature during welding is required to be controlled below 60 ℃, after welding It must be water-cooled immediately, and segmented welding is used at the same time. This symmetrical and dispersed welding sequence can increase the cooling rate of the joint and reduce the welding stress.
