Welding Requirements for Large Diameter Straight Seam Steel Tubes

Large diameter straight seam steel pipe welding, including pre-welding, welding and welding outside the three processes. The so-called pre-welding that is, after the steel pipe forming, the use of continuous high-speed gas shielded welding (MAG) method of forming steel pipe positioning welding. After the pre-welding, respectively, within the steel pipe, multi-wire submerged arc welding. In the case of high-speed gas-shielded pre-welding, there are currently two methods. One is the use of single-wire dual-power high-current high-speed gas protection pre-welding, such as the United States, Germany that is used in this way; the other is double-wire high-speed gas protection pre-welding, Japan is the use of this method. At present, more applications are monofilament high-speed gas protection pre-welding method, in a reasonable welding process conditions, can achieve not less than 7m / min high speed, and straight bead forming beautiful. As the pre-welding of the first step of welding, the quality is ensured. Pre-welding quality, not only its own quality problems, but also affect the follow-up, the quality of welding. Its quality requirements, targeted mainly as follows:

1, The weld should be continuous, and the appearance of shape to avoid uneven, in order to facilitate the final quality assurance of welding.
2, To ensure the penetration depth and the appropriate amount of welding, it is necessary to ensure that after welding does not crack, but also to make the phenomenon of burn-through when not produced.
3, To have a higher welding speed, in order to improve production efficiency.