Welding technology and requirements of stainless steel pipe fittings
The stainless steel pipes of different sizes, in accordance with the stainless steel pipe welding unique place, as far as possible to reduce the amount of heat input, so the use of manual electric arc welding and argon arc welding of two methods, d> with the diameter of 159 mm using the argon arc welding, manual arc cap. The TIG D is less than or equal to 159 mm. Stainless steel pipe welding technical requirements are as follows:
In manual arc welding, the welding machine adopts DC reverse welding, and the DC welding is adopted in the argon arc welding;
The welding should be welding wire for stainless steel wire brush off the surface oxide, and washing with acetone; electrode should be at 200-250 deg.c drying 1H, the;
Before welding, clean the oil in the range of 25 mm within the groove of the workpiece, and clean the 25 mm area on both sides of the groove with acetone;
When argon arc welding, the nozzle diameter is 2 mm, and the tungsten is a bowl of tungsten tungsten. The specification is 2.5 mm;
When argon arc welding of stainless steel, the back must be filled with argon to protect the back. Using the method of partial argon filling in the pipeline, the flow rate is 5-14L/min, and the positive argon flow rate is 12 13L/min.
When the weld backing welding thickness should be as thin as possible, and root fusion to become outstanding, the arc slope, such as arc shrinkage, application of grinding out. The arc extinguishing shall be carried out in the groove, and when the arc is extinguished, the arc pit shall be filled to prevent the crack in the arc pit.
Because the stainless steel pipe fittings for austenitic stainless steel pipe, to prevent the precipitation of carbide sensitization and intergranular corrosion, should strictly control the layer temperature and cooling rate after welding, welding interlayer temperature controlled at 60 DEG C, cooling after welding must immediately, at the same time by welding. This symmetrical and dispersed welding sequence can increase the cooling rate of the joint and reduce the welding stress.
Source: China Steel Pipes Manufacturer - Yaang Pipe Industry Co., Limited (www.yaang.com)