Matters needing attention in welding of stainless steel water pipes for water supply
When welding the stainless steel pipe, the grinding wheel used only for grinding stainless steel pipes; the steel wire brushes used and the tools to remove the slag are made of stainless steel; the stainless steel pipe surface is not allowed to be exposed to the flame processing place, otherwise the corrosion resistance of the stainless steel pipe will be damaged.
Stainless steel pipe welding operation, the use of short arc. Inert gas protection must be good when using gas shielded arc welding. When a solid core wire is used as a melting pole to weld a stainless steel pipe, the protective gas should not be used as a mixture of carbon dioxide. The carbon content of the weld of the stainless steel pipe will not be increased because of the slag protection.
Generally do not preheat, only a relatively thick stainless steel pipe before welding before heating 100-150 degrees.
In welding, the temperature between layers should be strictly controlled, less than 150 degrees.
Welding with smaller line energy should be used as far as possible.
Reverse formed gas shielded arc welding, the welding root must be protected by return gas or pure argon.
The ferrite content in the weld should be remeasured with an ferrite tester to ensure the pre determined ferrite content in the weld seam of the stainless steel pipe. The melting amount of base metal should be controlled below 35% of the whole stainless steel water pipe weld area.
For the austenitic stainless steel pipes with stabilizers to stabilize carbon, it is suggested that the filler materials with ultra low carbon free stabilizers and vice versa are recommended to prevent intergranular corrosion.
Because the shrinkage deformation of austenitic stainless steel pipe is large, it should be strengthened in clamping devices and positioning welding. It is not allowed to trace the traces of the base metal on the groove of the stainless steel water pipe.
To ensure the corrosion resistance of the welded joint, the surface should be bright, the residue and the color of the weld should be removed. The removal methods are grinding, pickling, shot peening, brushing or polishing. The smaller the surface roughness, the higher the corrosion resistance. Surface pickling can be carried out with various acid washing or pickling plaster, according to the prescribed acid pickling time, and then rinse clean water. The best way to remove color after welding is to use quartz sand for grinding.
Before repairing welding, we should also acid wash the surface of the groove. However, due to the rough surface of the old components, it is best to passivate the surface after pickling, then rinse it with water.
Only quartz sand or stainless steel particles are allowed during shot peening. After shot peening, the surface has metallic luster, but the surface is too rough. It should be passivated.
In the welding of stainless steel pipes, the copper block used for quenching is recommended to accelerate the cooling rate of the weld pipes of stainless steel pipes.