Welding skills of stainless steel bellows and flange pipe
Stainless steel bellows are widely used in oil, water and gas pipelines, and most of them have a certain pressure. The thin bellows are often need to welded, but it’s difficult because they are thin (about 0.2mm). Welding methods have fusion welding, brazing and so on. Here we introduce the argon tungsten arc welding of stainless steel bellows and stainless steel flanged pipes, the key to welding is to prevent burn through.
1.The preparation before welding
First we need clean oil and other dirt from the welded stainless steel bellows and flange pipe. If it is welding cracking and leakage, should be remove the original welding scar, flange straight pipe grinding the metallic luster, Stainless steel bellows straight pipe can’t grind and cleaning due to the thickness it’s too thin, the `application of hand emery cloth sand bright. Use hand emery cloth to polish it it’s a possible way.
Welding assembly: The best assembly gap is 0. Due to the processing and manufacturing error sometimes gap is too large, when do the welding it’s easy to burn through. The solution is to build a layer of surfacing on the overlapping place (generally 3 ~ 5mm) on the flange straight pipe, then machining or manual grinding to 0 ~ 0.05mm gap . If it does not fit, trim or grind the flange straight pipe outer diameter until it fits.
2.Welding machine selection: WS315type, DC
3.Welding material selection: ER308, ø 0.8mm
A). Welding parameters: Welding current 25 ~ 30A, Protection gas flow 4 ~ 7L/min.
B). The arc must be carried out on the flange pipe, the electric arc direct to the thick pipe, use the electric arc flame heating bellows, and welding wire to block the edge of the bellows, with melted stainless steel welding wire to melt the bellows.
C). During welding, the strip must be transported on the thick pipe, and short weld welding or spot welding shall be adopted.
D). During welding, always observe the melting of bellows. Generally, 1 ~ 3 molten pools are melted at a time. Continuous welding is not suitable, especially when the gap is large, it is very easy to burn through.
E). In short, the skill of arc welding between stainless steel bellows and stainless steel flange pipe (or other pipes) is that the arc can not directly point to the bellows, but use the residual heat of the arc to melt the bellows for welding.