Analysis of the causes of hydrogen-induced defects in straight seam submerged arc welded pipes and related measures

Hydrogen-induced defects in welds are related to the amount of hydrogen content. When the hydrogen content in the weld is low, hydrogen embrittlement occurs; when the hydrogen content in the weld is high, white spots often appear on the tensile or bending section; when the molten pool absorbs a large amount of hydrogen, pores will appear in the weld; when the diffused hydrogen content in the weld is high, the tensile stress is large and cold cracks will occur.

Causes of hydrogen-induced defects in straight seam submerged arc welded pipes

Hydrogen-induced defects in straight seam submerged arc welded pipes are related to oil stains and adsorbed water near the groove of the weld. Preventing water and oil from entering the welding pool is the main measure to prevent hydrogen-induced defects in welds. The following points can be used to control the oil and adsorbed water near the groove of the weld:

① The coupled water on the surface of the steel plate should be completely removed after the flaw detection, and the surface of the steel plate should be prevented from freezing in winter;

② Prevent the molding machine oil from dripping near the groove of the steel plate;

③ Before welding, check whether there is oil, water, and rust near the groove of the steel pipe. If there is, it should be removed before welding;

④ The desiccant in the compressed air dryer should be replaced regularly;

⑤ The steel plate cannot come into contact with oil during transportation, and the oil on the surface of the steel plate should be removed when loading;

⑥ The overhead crane in the welding area should stay in the position after the external welding as much as possible.

Measures to control hydrogen in the weld are:

1. Limit the hydrogen content in the welding material;

2. Remove rust, oil, adsorbed water, etc. on the surface of the welding wire and the groove of the weld before welding;

3. Reduce the hydrogen content in the weld through metallurgical treatment;

4. Control the welding process parameters;

5. Dehydrogenation treatment after welding. In the production process of straight seam submerged arc welded pipes, the hydrogen content in the weld is mainly controlled by the first two measures.