As stainless pipe fittings are variable in size, it is better to reduce the amount of heat input as far as possible in accordance with the unique welding of stainless steel pipe fittings. Therefore, we need to take the method of manual arc welding and argon arc welding. For those d>Φ159 mm, using argon arc as root welding and manual arc as cover welding, for those d≦Φ159 mm, all using Argon arc welding. Welding technical requirements of Stainless Steel pipe Fittings are as follows:
①The welding machine adopts the DC reverse connection when it is the manual arc welding, and the direct current when it is the Argon arc welding;
② Using stainless steel wire to brush off the oxidation surface of welding wire before welding and washing with acetone; The electrode should be dried in the temperature of 200-250 ℃ for an hour, you can use it whenever you need;
③ Cleaning oil pollution of the work piece on both sides of the slope within the range of 25 mm before welding, and using acetone to wash it within the same range;
④In argon arc welding, diameter of nozzle is φ2 mm; tungsten: extremely bowl tungsten whose specification is φ2.5 mm;
⑤when using argon arc welding to weld stainless steel pipes, the back must be filled with argon protection in order to ensure its forming. Adopting the method of partly argon filling in the pipeline, the flow is 5-14L/min, and the positive Argon flow volume is 12-13L/min.
The seam thickness should be as thin as possible at the root welding, so that it will weld with the root excellently. The arc should be a gentle slope, if there is a arc shrinkage, wear off it with polishing machine. In addition, The arc must be filled in the groove and the arc crater should be filled to prevent the cracks.
This stainless steel pipe fittings are austenitic stainless steel pipe. In order to prevent the carbide precipitation sensitization and intergranular decay, the interpass temperature and cooling rate after welding should be strictly controlled. Detailedly speaking, the temperature control between the layers should under 60 ℃ and the water should be cooled immediately after welding, adopting subsection welding at the same time. This symmetrical and dispersed welding sequence can not only increase the cooling rate of the joints but also can reduce the welding stress.