Welding process of spiral steel pipe

The most common connection method for spiral pipes is welding, which belongs to the traditional connection method of spiral steel pipes, which is far from meeting the market demand in terms of safety, sealing performance, cost space, and emergency repair efficiency.

(1) Manual arc welding. Due to the flexibility of manual welding and the low requirements for welding equipment, at present, manual arc welding still accounts for 40% to 50% of the workload of outdoor pipeline welding.

(2) Cellulose downward welding process. The cellulose downward welding process is a welding process commonly used at home and abroad, and it is applied to the welding of all thin-walled large-diameter pipes including steels below X70. The welding speed is fast, the root welding performance is good, the qualified rate of weld seam radiographic flaw detection is high, and the economy is excellent.

(3) Low-hydrogen type vertical welding. Compared with the cellulose downward welding process, this process has a slower root welding speed, and is mainly used for welding pipes or thick-walled pipes with extremely harsh weather conditions, transporting acidic gas and high-sulfur oil and gas media, and requiring high low-temperature toughness.

(4) Stand down to the cellulose electrode for bottom welding, and CO2 gas shielded welding to fill the surface. Due to the high productivity and low cost of CO2 welding, it has been continuously promoted and applied in recent years. However, for oil and gas pipeline welding, in order to realize all-position welding, it must be completed in a small current range with a short-circuit transition method, and the short-circuit transition method is used for Backing welding is prone to defects such as incomplete penetration. Therefore, one-sided welding is achieved by using the vertical cellulose electrode as a primer, and the back is formed, and then the surface is filled with high-efficiency CO2 gas shielded welding.

(5) Semi-automatic welding with self-shielded flux-cored wire. Self-shielding flux-cored wire semi-automatic welding is especially suitable for outdoor windy occasions. It does not use CO2 and relies on the gas protection generated by the flux core. It has good wind resistance and can be used for all-position welding with high deposition rate of pipelines. At present, the self-shielding flux-cored wire produced by Lincoln Company is recognized by various countries. Its brands include NR-207, NR-204-H, NR-208-H, etc., which can be applied to the establishment of X70, X80 and other pipelines. To welding. However, when this method is used for rooting welding, the weld root is prone to unfused defects.

(6) CO2 gas protection semi-automatic or fully automatic welding of high-performance welding machine. At present, foreign countries have successively produced high-performance power supplies for real-time control of welding current and voltage waveforms or power control of output characteristics. Lincoln's STT surface tension transition welding technology belongs to the category of waveform control. Based on the improvement of the performance of the welding equipment, the semi-automatic and fully automatic CO2 gas shielded welding of the pipeline can be well realized, which greatly improves the welding efficiency and welding quality.

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