The most important feature of erw steel pipe is no foreign filler metal, heating speed, high production efficiency, which is an advantage, but also its shortcomings, which is no filler metal, the filler alloy will not benefit approach to improve the weld properties element; heating temperature is high, the sound is short, the welding temperature gradient is greater, so that some of the steel is susceptible to hardening phase and organize stress make the weld fragility, comprehensive mechanical performance in the welding process. Therefore, the ERW pipe weld joint must be carried out after the remedial measures - weld heat treatment to improve the organization, eliminate stress and improve performance.

In recent years, due to the development of cold regions and marine fields, for ERW pipe to provide a more broad prospects for development, which requires ERW pipe has good low temperature and corrosion resistance. But now, many manufacturers of ERW steel pipe welds poor low-temperature toughness, FATT value is high, greatly limiting its scope. ERW pipe weld low temperature toughness of the steel pipe has become such an important indicator of the level of technology.

ERW pipe weld joint heat treatment process online, in general, the heating method is generally induction heating; sensors in order to ensure the accuracy of the weld heating, advanced automatic welding unit mostly equipped with photoelectric tracking system: In order to ensure the stability of the heating temperature resistance, and is equipped with automatic temperature control systems, process types are mostly used in addition to normalizing weld, weld annealing process, some manufacturers in order to improve the impact toughness of the weld, for high-strength steel, using the transfer of heat treatment process, adjusting quality technology to make the weld grain has been refined, improved weld toughness. In addition, there normalizing plus tempering, quenching and tempering, and thermomechanical treatment process research and development recently. Currently, world terms, the most widely used weld heat treatment or weld normalizing process. Weld normalizing process commonly used IF (1-10KHz) power, but considering the oscillation generated noise and other factors, it is best to use 1-3KHz. You can 50.8mm diameter steel pipe welds above normalized. Normalizing treatment can significantly improve the performance of the weld flattening, the process parameters include: maximum heating temperature, heating rate, holding time and water-cooled starting temperature.

ERW pipe weld line go through a normalizing heat treatment, secondary normalizing, quenching and tempering, quenching and other technology to enhance the role of its toughness is unlikely. To take full advantage of high toughness steel controlled rolling potential advantages and make ERW pipe weld and base metal reached "and other tough fit", so this process must be following: general normalizing after treatment, the use of the heated area of the weld heat-softened, the pipe-bend resistance than other regions significantly reduced features, use of U & R (Upsetting and Rolling) "method, the weld region to produce a certain compression ratio-bend, then cooled, in order to improve the toughness of the weld.