How to weld for large-diameter welded steel pipe at low temperature?

Welding large-diameter steel pipes under cold conditions can be challenging due to the increased cooling rate of the welded joint, which heightens the tendency for cracking, especially in the first weld of heavy structures. To mitigate these risks, the following steps should be taken.

1. Avoid Bending, Correction, and Assembly at Low Temperatures: Perform these operations at higher temperatures to prevent additional stress on the material.

2. Preheating: Ensure the welding process strictly maintains the interlayer temperature, which should not fall below the preheating temperature. This helps to reduce the cooling rate and minimize the risk of cracking.

3. Use Low-Hydrogen or Ultra-Low Hydrogen Welding Methods: This reduces the risk of hydrogen-induced cracking in the weld.

4. Continuous Welding: Complete the entire seam in one continuous weld to avoid interruptions, which can introduce stress points and increase the risk of cracking.

5. Adjust Welding Parameters for Tack Welds: Increase the welding current and reduce the welding speed during positioning welding to increase the cross-sectional area and length of the tack welds. Preheating may be necessary to ensure proper fusion and reduce the risk of cracking.

6. Avoid Arc Strikes Outside the Weld Groove: Ensure that the arc is struck only within the weld groove and that the crater is properly filled when extinguishing the arc to avoid creating stress concentrations and potential crack initiation points.

By following these steps, the integrity of the welded joint can be maintained, and the risk of cracking can be significantly reduced when welding large-diameter steel pipes in low-temperature conditions.