Welding techniques of stainless steel bellows and flanges

 

Stainless steel bellows are widely used in oil transportation, water conveyance and gas transmission pipelines, and most of them are under certain pressure. This thin bellows is often welded, because it is thin (about 0.2mm), so welding is difficult. Welding methods are welding, brazing and so on. The TIG welding of stainless steel bellows and stainless steel flanges is introduced here. The key to welding is to prevent burn through.

 

Second, pre welding preparation

 

1, clean the stainless steel bellows and grease stains on flanges. If the welding seam cracks and leakage, the original welding scar should be cleaned out, the flange pipe straight pipe grinding out metal luster, corrugated pipe straight pipe because too thin, can not grinding, grinding cleaning, the application of sand cloth sand bright.

 

2, welding assembly: the best assembly gap is 0, because the manufacturing error has time gap too big, welding melt easy to burn through, the solution can be overlapped on the flange pipe straight pipe (general 3 ~ 5mm) overlay one layer, machined to 0 ~ 0.05mm clearance or manual grinding. If it can not be sleeved up, the car should be small or grind small flange pipe straight pipe outer diameter until suitable.

 

3, welder selection: type WS315, direct current connection.

 

4, selection of welding material: ER308, O 0.8mm

 

Third.welding operation

 

1, welding parameters: welding current 25 ~ 30A, protective gas flow 4 ~ 7L/min.

 

2, the arcing must be carried out on the flange tube, the arc should be on the thick tube, the bellows are heated by the arc flare, and the welding wire is used to prevent the bellows, and the melted stainless steel wire is used to melt the bellows.

 

3, welding must be carried out on thick pipes, welding by short welding or spot welding.

 

4, when welding, the melting of bellows should be observed and 1~3 molten pools are melted at one time. It is not suitable for continuous welding. It is very easy to burn through when the gap is large.

 

5, in a word, the arc welding of stainless steel bellows and stainless steel flanges (or other pipes) is a coincidence that the arc can not directly point to the bellows, but the welding with the residual heat of the arc is used to melt the bellows.