Frequently Asked Questions on Welding of Long Distance Pipeline Construction

Home - News - Line Pipe News

Frequently Asked Questions on Welding of Long Distance Pipeline Construction

Frequently Asked Questions on Welding of Long Distance Pipeline Construction

1. Slag inclusion

Reason: Because long-distance pipelines are mostly filled and covered with the semi-automatic downward welding process using flux-cored wire, the top wire phenomenon often occurs when the semi-automatic equipment has gap failures. At this time, the welding wire penetrates into the molten pool, When the pool is rapidly cooled and ignited again, the weld is often wrapped with metal debris or slag, which causes slag inclusion.

Measures: Bevel should be carefully cleaned before root welding, and slag should be carefully cleaned during filling and cover welding.

2. Stomata

Cause: The pores in the filling layer are mainly caused by the high arc voltage during the semi-automatic welding of the self-protecting flux core.

Measures: In the welding process, select the appropriate arc voltage and wire feed speed, maintain a certain wire extension length, and control the appropriate welding speed when downward welding.

3. the root is not welded

Reason: The main reason is that the gap of the pair is too small or the blunt side is too thick.

Measures: Before the welding, carefully grind and group the butt welds to ensure that the wire or electrode can smoothly penetrate into the root of the groove during root welding; when the root welding cannot dissolve, grind the root gap of the application and adjust the welding parameters appropriately. .

4. crack

Cause: Forced pairing often results in cracks during welding.

Measures: 1) Avoid forced pairing; 2) Preheat before welding, and moderately increase the thickness of the root bead. After root welding is completed, heat welding, filling, and covering are performed immediately.

5. burn through

Cause: Caused by too thin root bead or improper welding process parameters.

Measures: The root bead should not be too thin, it is better to be 3mm thick; the root welding process parameters should not be too large; the welding should be stopped immediately after burn-through, the groove angle and root clearance need to be polished, and then root welding and hot welding should be performed again. To complete this process.