Welding Knowledge of Oil And Gas Steel Pipelines

With the development of the petroleum industry, steel pipeline transportation of oil and gas has developed rapidly due to its safety, economy, expertise, and efficiency. Long distance, large diameter, and high pressure are becoming the development direction of onshore oil and gas transmission steel pipelines. Pipeline steel x56-X70 series high-strength steel has been widely used in steel pipeline construction, and X80 advanced strength steel pipelines are also in the development and application stage, such as in Germany In 1993, an X80 steel pipeline with a diameter of 1200mm and a length of 126km was built. In 1994, Canada trial-built a 1200m-\3km X80 steel pipeline. Due to the rapid construction of oil and gas steel pipelines, steel pipeline welding processes, welding equipment, and welding materials have also developed greatly. Many manufacturers have participated in market competition. There are many mature welding equipment and welding materials for steel pipeline construction at home and abroad. The following is a survey of steel pipeline welding equipment and materials produced by famous foreign manufacturers for reference.
1. Overview of commonly used welding processes for oil and gas steel pipelines at home and abroad. In the 1970s and 1980s, steel pipeline welding was mainly manual welding with downward cellulose electrodes and semi-automatic C02 welding. Since these methods are manual operations, they are inefficient and the welding quality is poor. Restricted by the level of manual skills, in the mid-1980s, due to the continuous development of power electronics technology and computer technology, the control technology of welding equipment entered the era of intelligence, thus creating conditions for the successful implementation of new equipment and new processes for steel pipeline welding automation. , which has greatly improved the welding efficiency and welding quality of steel pipelines. For example, the STT (The Surface Tension Transfer) C02 gas-shielded welding power source technology and equipment developed by Lincoln Company has a soft arc, minimal spatter, and excellent welding. The quality of bottom welding has attracted the attention of the world and has become one of the preferred methods for steel pipeline welding, especially bottom welding. Another example is the all-position automatic welding equipment for steel pipelines produced by MAGENATECH, which applies adaptive control technology, which not only overcomes the horizontal constraints of manual operation but also greatly improves welding efficiency and quality. To summarize, the current construction techniques for steel pipeline welding mainly include the following:
1.1 Use cellulose downward welding rods for manual welding. When there are steel pipelines with serious hydrogen sulfide corrosion or steel pipelines running in cold environments, use low hydrogen type vertical downward welding rods for welding. Due to the flexibility of manual welding and low requirements for welding equipment, manual arc welding still accounts for 40-50% of the workload of outdoor steel pipeline welding. For example, in recent years, the steel pipeline project from Shaanxi to Beijing in my country was purchased from Bole Company More than 1,000 tons of various cellulose welding rods have been produced. It is predicted that the annual demand for welding rods for my country's oil and gas steel pipelines will range from 3 to 5,000 tons in the next few years, and there is an increasing trend.
1.2 Weld the bottom of the cellulose electrode vertically, and the C02 gas shielded welding filler surface. Due to the high productivity and low cost of C02 welding, this method has been continuously promoted and applied in recent years. However, for oil and gas steel pipeline welding, all-position welding must be completed within a smaller current range using the short-circuit transition method. The short-circuit transition method is used Because primer welding is prone to defects such as incomplete penetration, vertical downward cellulose electrodes are used to achieve single-sided welding and back-side forming, and then the highly efficient C02 gas-shielded welding is used to fill the surface. This process is more commonly used.
1.3 Self-shielded flux-cored wire semi-automatic welding Self-shielded flux-cored wire semi-automatic welding is especially suitable for outdoor windy occasions. It does not use C02 and relies on the gas protection generated by the flux core. It has good wind resistance and can be used for pipes with high deposition rates. For all-position welding, the self-protected flux-cored welding wire produced by Lincoln Company is currently recognized by various countries. Its brands include NR-207, NR-204-H, NR-208 H, etc., which can be applied to x70, X80, and other steel pipelines. The vertical downward welding. However, this method also has the defect that the welding root is prone to not being fused during bottom welding.
1.4 C02 gas-shielded semi-automatic or fully automatic welding of high-performance welding machine. As a result of in-depth research on the control technology of the C02 gas-shielded welding short-circuit transition process, foreign countries have successively produced high-performance power supplies that can timely control the welding current and voltage waveforms or control the output characteristics of electric energy. The aforementioned sTT surface of Lincoln Company of the United States Tension transfer welding technology belongs to the category of waveform control. Based on the improvement of the performance of welding equipment, semi-automatic and fully automatic 02 gas-shielded welding of steel pipelines can be realized, which greatly improves the welding efficiency and welding quality. In addition, automatic IC welding is also used for pipe welding in factories. This method has good quality but low production efficiency.
2. Welding materials for steel pipeline welding
2.1 Cellulose vertical downward welding rod