Double wire welding wire extension length on welding quality as well. Wire elongation is too large, the resistance is large, the heat resistance will increase, resulting in reduced penetration, poor fusion, flux than the height of the stack increases, increase the amount of weld projections. In addition, the contact tip heat increased, even red-hot oxide overheat and shorten the life of the contact tip. Wire elongation amount is too small, the impact of flux than the height of the stack, or even open arc, penetration increases, projecting height decreases, affecting weld.
Spiral welded pipe production, the first multi-purpose wire diameter 4 mm, the diameter of the wire after the multi-purpose 3 mm. Former wire in order to ensure penetration, DC reverse, requiring high current, low voltage, so the first wire elongation should try to choose shorter, but not too short, usually 28 ~ 40 mm. After AC wire, requiring low current, high voltage, in order to increase the weld width to ensure good weld, so after the wire elongation choose slightly longer. Because after the wire diameter is generally thinner than before the wire and welding wire around the pitch and they have a small inclination, prone to cross two wire contacts and seriously undermine the stability of the welding process, so the elongation should not be too long, the general choice 24 ~ 36 mm.
