The biggest difference between high-frequency electric resistance welded pipes and seamless steel pipes is that ERW has weld seams, which is also the key to the quality of ERW steel pipes. Modern ERW steel pipe production technology and equipment, due to the unremitting efforts of the world, especially the United States over the years, have made ERW the seamlessness of steel pipes has become a more satisfactory solution.

Some people divide the seamlessness of ERW steel pipes into geometric seamlessness and physical seamlessness. Geometric seamless is to remove the internal and external burrs of ERW steel pipes. Due to the continuous improvement and perfection of the internal deburring system structure and cutting tools, the deburring of large and medium-diameter steel pipes have been better handled. The internal burr can be controlled within the range of -0.2mm～+0.5mm. Physical seamlessness refers to the difference between the metallographic structure of the weld and the base metal, which leads to a decrease in the mechanical properties of the weld area, and measures need to be taken to make it uniform.

The high-frequency welding heat process of ERW steel pipe forms a temperature distribution gradient near the edge of the tube billet, forming a melting zone, a semi-melting zone, an overheated structure, a normalizing zone, an incomplete normalizing zone, and a tempering zone. Among them, because the welding temperature is above 1000 ℃ to form a superheated zone structure, the austenite grains grow rapidly, and a hard and brittle coarse crystal phase will be formed under cooling conditions. In addition, the presence of temperature gradients can cause weld stress. In this way, the mechanical properties of the weld zone are lower than those of the base metal.

The physical seamlessness is realized through the local conventional heat treatment process of the weld, that is, the medium frequency induction heating device is used to heat the weld zone to AC3 (927℃), and then proceed for 60m. The length and speed of the air-cooling process are 20m/min, and water cooling is performed when necessary. This method achieves the purpose of eliminating stress, softening and refining the structure, and improving the comprehensive mechanical properties of the welding heat-affected zone.

At present, advanced ERW units in the world generally use this method to process welds and have achieved good results. The high-quality ERW steel pipe not only cannot distinguish the weld seam but also has a weld coefficient of 1, which realizes the matching of the weld seam area and the base material.

At the same time, the advantage of ERW steel pipe is that it uses a hot-rolled coil as raw material, and the uniformity of wall thickness can be controlled at about ±0.2mm. Both ends of the steel pipe shall be delivered according to the American APL standard or GB/T9711.1 standard, and the end chamfers shall be cut to length. In recent years, various natural gas pipeline network projects and gas companies have widely used ERW steel pipes as the main pipe material for urban pipeline networks. If you are looking for high-quality ERW steel pipes, welcome to contact us.

BAOLAI is a professional custom steel pipe manufacturer, our products mainly include seamless carbon steel pipe, welded carbon steel pipe, alloy steel pipe and so on. The main purpose of pipelines is to transport liquids or gases, including oil, gas and water, underground. We offer full size steel pipe from 1/8" to 50" OD and wall thicknesses from sch10 to SCH XXS. BAOLAI has API 5L, API 5CT, CE, UL, FM, ISO and other certificates to ensure the quality of steel pipes.