MIG spiral seam welding of steel pipe - formed by bending steel plate and using internal and external welding at high speed

摘要

A moving steel strip is continuously bent into pipe and welded internally (IW) and externally (EW) along the spiral butt joint. Both IW and EW use (a) a solid consumable wire electrode (CEW), 3-8 mm dia. (b) welding current (WC) 600-200 amps.; (c) welding voltage (WV) 20-36 V; (d) an inert gas contg. by vol. 5-50% CO2 and/or 1-10% O2, this mixt. being fed at 70/400 litres/minute per each CEW. Further (E) IW uses a CEW (1) within 20 degrees upstream of the point (J) at which the edges of the strip meet, where (J) is the 6 o'clock position and a CEW (2) is used within 12 degrees downstream of position (J); (f) EW follows at a point (Jusing one or more electrode within 30 degrees upstream of point (J When the IW and EW use only one CEW each, both are pref. within 12 degrees upstream of point (J) and (Jmay be used downstream of both points to protect the cooling welds. High welding speeds producing high quality welds which are not concave.