Large diameter straight seam welded pipe welding requirements

Large-diameter straight seam steel pipe welding, including pre-welding, welding and welding three processes. The so-called pre-welding is the use of continuous high-speed gas shielded welding (MAG) after the steel pipe is formed, the positioning welding of the steel pipe. After pre-welding, multi-wire submerged arc welding is performed in the steel pipe. 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 shielded pre-welding, such as the United States, Germany that is used this way; the other is double wire high-speed gas shielded prewelding, Japan is to use this method. At present, more and more applications of monofilament high-speed gas shielded pre-welding methods, under a reasonable welding process conditions, can achieve high speeds of not less than 7m/min and straight seams are beautifully formed. As the first step of the welding, the welding quality is guaranteed. The quality before welding, not only its own quality problems, but also affect the follow-up, welding quality. Its quality requirements, the main goals are as follows:


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