What is an ERW steel pipe? The biggest difference between ERW steel pipe (Electric Resistance Welding, abbreviated as ERW) and seamless steel pipe is that ERW has a weld seam, which is also the key to the quality of ERW steel pipe. Modern ERW steel pipe production technology and equipment, due to the international Especially with the unremitting efforts of the United States and other countries over the years, the seamlessness of ERW steel pipes has been solved satisfactorily. Some people divide the seamlessness of ERW steel pipes into geometric seamlessness and physical seamlessness. Geometric seamlessness means clearing ERW steel pipes. Internal and external burrs. Due to the continuous improvement and improvement of the structure of the internal burr removal system and the cutting tools, the internal burrs of large and medium-diameter steel pipes have been better processed. The internal burrs can be controlled at around -0.2mm~+O.5mm and are physically free. Seamization refers to the difference between the metallographic structure inside the weld and the base metal, resulting in a decrease in the mechanical properties of the weld area. Measures need to be taken to make it uniform and consistent. The high-frequency welding thermal process of ERW steel pipes causes the tube to blank The temperature distribution gradient near the edge forms a molten zone, a semi-melted zone, a superheated structure, a normalizing zone, an incomplete normalizing zone, a tempering zone, other characteristic areas. Among them, the structure of the superheated zone is austenite due to the welding temperature above 1000°C. The grains grow rapidly, and a hard and brittle coarse crystal phase will be formed under cooling conditions. In addition, the existence of a temperature gradient will generate welding stress. This results in a situation where the mechanical properties of the weld area are lower than those of the base material and the physical seamlessness is achieved. It is through the local conventional heat treatment process of the weld seam, that is, using a medium frequency induction heating device to heat the weld seam area to AC3 (927°C), and then perform an air cooling process with a length of 60m and a speed of 20m/min, and then water cooling when necessary. The use of this method can achieve to eliminate stress, soften and refine the structure, and improve the comprehensive mechanical properties of the welding heat-affected zone, currently, the world’s advanced ERW units have generally adopted this method to process welds, and have achieved good results. High-quality ERW steel pipes are not only The weld seam that cannot be identified, and the weld seam coefficient reaches 1, achieving a match between the weld area structure and the base material. ERW steel pipes have the advantage of using hot-rolled coils as raw materials, and the wall thickness can be uniformly controlled at about ±0.2mm. The two ends of the steel pipe According to the American APl standard or GB/T9711.1 standard, it has the advantages of end beveling and fixed-length delivery. In recent years, various natural gas pipeline network projects and gas companies have widely adopted ERW steel pipes as the main steel pipes in urban pipeline networks.