Special points for special attention when welding stainless steel welded pipes
1. When welding stainless steel welded pipe, the grinding wheel used for grinding can only be used for grinding stainless steel welded pipe; the wire brush used and the tool for removing welding slag are all made of stainless steel; the surface of stainless steel welded pipe is not allowed to be exposed to flame processing. Otherwise, the corrosion resistance of the stainless steel welded pipe will be damaged.
2. When welding stainless steel welded pipe, apply short arc. In the case of gas shielded welding, inert gas protection must be good. When the solid wire is used as the molten-welded stainless steel welded pipe, the shielding gas should not be mixed with carbon dioxide; the resistant core wire is not protected by slag, and the carbon content of the stainless steel welded pipe weld is not increased by the carbon dioxide gas.
3, generally do not preheat, only thicker stainless steel welded pipe is preheated 100-150 degrees before welding.
4. In the welding, the interlayer temperature should be strictly controlled, less than 150 degrees.
5. Welding with a small amount of wire energy should be used as much as possible.
6. Gas shielded welding of reverse surface molding, the root side must be protected with reducing gas or pure argon.
7. Considering the pre-determined ferrite content in the weld of the stainless steel welded pipe, the actual ferrite content in the weld should be re-tested with a ferrite tester. Generally, the melting amount of the base metal should be controlled below 35% of the cross-sectional area of the entire stainless steel welded pipe.
8. For austenitic stainless steel welded pipes with stabilizer added to stabilize carbon, it is recommended to use ultra-low carbon fillers without stabilizers and vice versa to prevent intergranular corrosion.
9. Due to the large shrinkage deformation of the austenitic stainless steel welded pipe, it should be strengthened on both the clamping device and the positioning welding.
10. It is not allowed to have traces of arc scratching of the base metal at the groove of the stainless steel welded pipe.
11. In order to ensure the corrosion resistance of the welded joint, the surface should be bright, and the color of the residue and weld should be removed. The removal method is grinding, pickling, shot blasting, brushing or polishing. The smaller the surface roughness, the higher the corrosion resistance. For surface pickling, various pickling solutions or pickling pastes can be used, and rinsed with clean water according to the prescribed pickling time. When removing the color after welding, the best way is to use quartz sand for grinding.
12. Before repairing the weld, the surface of the groove should also be pickled. However, since the surface of the old component is rough, it is preferable to passivate the surface after pickling, and then rinse it with water.
13. Only quartz sand or stainless steel granules are allowed for shot peening. After the shot peening, the surface has a metallic luster, but if the surface is too rough, it should be passivated.
14. In the welding of stainless steel welded pipes, in order to speed up the cooling speed of stainless steel welded pipe welds, it is recommended to use quenching copper pads.