One, overview Stainless steel bellows are widely used and have applications in oil, water and gas pipelines, and most of them still have some pressure. Such thin corrugated tubes are often welded, and because of the thinness (about 0.2 mm), welding is difficult. Welding methods include welding, brazing, and the like. Here, the tungsten argon arc welding of stainless steel bellows and stainless steel flanged tubes is introduced. The key to welding is to prevent burn through.
Second, pre-weld preparation
Clean the stainless steel corrugated pipe to be welded and the oil on the flange pipe. If it is cracked and leaked at the weld, the original weld bead should be cleaned off, and the metal luster should be ground at the straight pipe of the flange pipe. The straight pipe of the bellows is too thin to be ground and polished, and the sand is brightened by hand sand. Just fine.
Welding assembly: the best assembly clearance is 0, due to processing error, sometimes the gap is too large, the welding is easy to burn through, the solution can be overlapped on the straight pipe of the flange pipe (usually 3 ~ 5mm) heap One layer of welding, machined to 0 ~ 0.05mm gap or hand grinding. If the sleeve does not go up, the small outer diameter of the straight tube of the flange tube should be small or small until it is suitable.
Welding machine selection: WS315 type, using DC positive connection.
Welding consumables selection: ER308, Ø0.8mm
Third, the welding operation
Welding parameters: welding current 25 ~ 30A, protective gas flow 4 ~ 7L / min.
The arc must be carried out on the flange tube, the arc should be on the thick tube, the arc outer flame is used to heat the bellows, and the wire is used to block the edge of the bellows, and the bellows is melted with the molten stainless steel wire.
Welding time strip must be carried out on thick tubes, using short weld welding or spot welding for welding.
When welding, it is necessary to observe the melting condition of the bellows at all times. Generally, one to three molten pools are melted at a time, which is not suitable for continuous welding, especially when the gap is large.
In summary, the arc welding of stainless steel bellows and stainless steel flanged tubes (or other tubes) is based on the fact that the arc cannot directly point to the bellows, and the bellows is used to weld the bellows.