High frequency straight seam pipe production knowledge

Resistance high frequency straight seam welded pipe (Electric hold Welding, referred to as ERW) with seamless steel tube the biggest difference lies in the ERW a weld, this also is the key of the ERW steel tube quality. Modernization of ERW steel pipe production technology and equipment, due to the international, especially the years of unremitting efforts, such as the United States made the seamless ERW steel pipe have satisfactory solution. Someone ofERW steel pipe seamless tumble into geometric seamless and physical seamless. Seamlessly geometry is inside and outside the burr removal of ERW steel pipe. Due within the burr removal system's structure and tools of continuous improvement and improvement of the steel pipe within the burr removal of large and medium caliber have had a better processing. Within the burr can be controlled in 0.2 mm ~ + o. 5 mm or so. Physical seamlessly refers to the inside of the weld microstructure and the difference between the parent metal and led to the decrease of the mechanical properties of weld area, some measures are needed to make it uniform and consistent. ERW steel pipe, high frequency welding thermal process caused the tube billet temperature gradient near the edge, and formed the melting zone, half melting zone, overheating organization, is fire area, incomplete area is fire area, back to the fire area and other features. The overheated zone tissue due to welding temperature above 1000 , the austenitic grain size grew up sharply, under the condition of cooling can form the coarse grain of hard and brittle phase, furthermore the existence of the temperature gradient can produce welding stress. Thus formed the mechanical properties of the weld area is lower than the parent metal, physical seamless steel tube is weld local conventional heat treatment process by using medium frequency induction heating device is the area of the welding heat in the AC3 (927 ), and then to 60 m length and speed in air cooling process of 20 m/min, water-cooled again when necessary. This method is used to eliminate stress, soften and refine the organization, improving the purpose of the welding heat affected zone comprehensive mechanical performance. At present, the world's advanced ERW unit has been widely used this method to deal with weld, has obtained better effect. High grade ERW steel pipe not only unable to recognize weld, and the welding seam coefficient reaches 1, implements the weld area and matching of the parent metal. The ERW steel tube by using hot rolled plate as raw material, wall thickness can be controlled around + / - 0.2 mm, tube two-terminal press American standard or standard, GB/T9711.1 APl repair end groove, specified length of delivery, etc. In recent years, the natural gas pipe network engineering and gas companies has been widely used in ERW steel tube as the main pipes of city pipe network.