ERW steel pipe characteristics

　　ERW steel pipe and SSAW steel pipe can meet the requirements of oil and gas transmission pipeline. For medium calibre（ Ф ERW steel pipes are mostly used for steel pipes below 630mm), and spiral submerged arc welded pipes are generally only used for low-pressure fluid transmission, civil buildings, structures and pile driving pipes.

　　Electric Resistance Welded steel pipe (ERW steel pipe for short) has many advantages such as high productivity, low cost, high dimensional accuracy and beautiful appearance. In recent years, all countries are actively studying to replace seamless steel pipe and spiral seam welded steel pipe with ERW steel pipe. In industrialized countries, the diameter of Ф Below 610mm, the proportion of ERW has reached about 70%. In the past, due to the poor reliability of the weld, the scope of use was greatly limited.

　　(1) The research on welding mechanism of ERW steel pipe has made gratifying achievements, and the welding process is optimized under the guidance of theory. All optimized parameters are controlled by computer, which improves the weld quality.

　　(2) Fluorescent line positioning technology is adopted for weld annealing, so that the annealing is carried out strictly at the specified position, so as to further improve the weld quality.

　　(3) The FATT value of the early ERW steel pipe weld zone is much higher than that of the base metal, with a maximum difference of 40-50 degrees. Due to the progress of metallurgical technology, the FATT value of the base metal of welded pipe can be as low as about - 70-80 degrees, which can still meet the user's requirements even if there is a certain difference between the two.

　　(4) Due to the application of automation and ultrasonic testing technology, the automatic tracking online detection of ultrasonic can be realized, which further reduces the probability of weld seam defects due to missing detection.