The most important feature is that no foreign ERW weld filler metal, heating speed, high production efficiency.
This is its advantages, but also its shortcomings. No filler metal, the filler alloy can not benefit approach elements improve weld properties; heating temperature is high, when the sound is short, the welding temperature gradient is greater, so that in the welding process, for certain steel grades and tissue prone to hardening phase stress, the weld fragility, comprehensive mechanical performance. Therefore, the need for post-weld seam ERW remedies - 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 high value, greatly limiting its scope. ERW steel pipe weld low temperature toughness of the steel pipe technology has become such an important indicator of the level.
Weld line heat treatment process, in general, heating is generally induction heating; in order to ensure the weld heat sensor accuracy, advanced automatic welding unit mostly equipped with photoelectric tracking system: In order to ensure the stability of the heating temperature, 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 weld toughness, for high strength steel, using the transfer of heat treatment process, quenching process weld grain has been refined to improve the toughness of the weld.
ERW steel pipe weld heat treatment, its metallurgical testing, including macro and micro parts. Macroscopic examination should measure the weld area is completely normalizing zone and incomplete normalizing zone width, and in the weld fusion line symmetrical situation. Normal morphology should be: the fusion line both sides of the heat-affected zone with good symmetry, after heat treatment area will be fully normalizing welded HAZ fully inclusive.
The only way to explain the process of heat treatment, heat sensor and a good pair of weld heat treatment temperature is appropriate. If the heat-affected zone around the fusion line distribution asymmetry, then the heat treatment, heat sensor deviates from the weld center, metallographic examination should this information timely feedback to the site operators to quickly adjust.
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