The biggest difference between resistance welding (ERW) steel tubes and seamless steel tubes is that ERW, if welded, is the key to the quality of ERW steel tubes. The modern
ERW steel pipe production process and equipment have made the
ERW steel pipe a satisfactory solution for the international community, especially the unremitting efforts of the United States and other years. This is ERW welded seamless steel tube is divided into geometric seamless and physical seamless. Geometric seams eliminate internal and external failures. Due to the structure and tools of the internal burr removal system, the burr removal of large and medium-sized steel pipes is well handled. Glitches can be controlled from -0.2mm to +0.5mm. Physical seamlessness means that there is a difference in the microstructure of the weld metal and the base metal, which results in a reduction in the mechanical properties of the weld zone and measures must be taken to make it uniform. The high-frequency welding heat process produces a temperature gradient near the edge of the tube in the ERW steel tube, forming distinctive structures such as melting, semi-melting, and overheating zone structures, specifications, incompletely normalized and tempered areas. In the overheating zone, the austenite grains suddenly grow up at a welding temperature higher than 1000° and form a hard and brittle coarse grain phase under cooling conditions. In addition, the presence of a temperature gradient will produce welding stress. In this way, the mechanical properties of the formed weld are lower than in the base material zone. The physical seamless steel pipe is heated by the welding zone to Ac3 (927°C) and then 60m long by means of a local conventional heat treatment process using an intermediate frequency induction heating device. The speed of meters/minute, when necessary, then cooling with water. This method eliminates stress, softens and refines the structure, and improves the mechanical properties of the integrated heat affected zone. At present, the world's most advanced ERW unit has been widely used in this method of welding, and has achieved good results. The high-quality ERW pipe can not only be said, welded, and the weld coefficient of 1 can achieve the welding area of the organization and the base metal.
