LSAW steel pipe induction loop should be as close to the position of squeezing rollers, steel internal stress is small and evenly distributed, which can effectively prevent stress corrosion cracking, high dimensional accuracy, easy on-site welding construction, if the induction loop from the squeeze roll farther, the effective heating time is longer, wider heat-affected zone, weld strength decreases; conversely, inadequate weld edge heating, after extrusion molding adverse insufficient heat input, the weld edge is heated up to a temperature of less than weld metal structure remains remains solid, formed unfused or weld penetration; insufficient when the heat input, the weld edge is heated more than the welding temperature, resulting in over-burning or droplet weld formation Cave. . Impedance is one or a group Welded dedicated magnet impedance the cross-sectional area is usually not less than 70% of the inner cross-sectional area of the pipe, and its role is to make the induction ring, tube seam edge of the magnet forming a magnetic induction loop, generating proximity effect, the vortex heat concentrated in the vicinity of the tube weld the edges, so that the edge of the tube is heated to welding temperature. After using the pre-finish welding the welding process, welding process is stable and high weld quality. Straight seam steel pipe impedance Used in dragging a wire tube, the center position should be relatively fixed position near the center of squeeze rollers.
Pipe inside burr is generally not clear. After the two edges of the tube is heated to welding temperature, oil pipes in the extrusion of squeeze rollers form a common metal grain mutual penetration, crystallization, eventually forming a strong weld. Soldering temperature is mainly affected by the high frequency eddy current thermal power, according to the correlation equation shows that the high-frequency eddy current thermal power is mainly affected by the current frequency, the eddy current heating power and current proportional to the square of the excitation frequency; and also by the current excitation frequency of the excitation voltage, current and capacitance, inductance effects. If the pressing force is too small to form a common crystal number is small, the weld metal strength is reduced by the force will produce cracking; weld burr generated by the welding and extrusion, need to be cleared. Removal method is the rack fixed cutter, pipe by rapid movement of the burr gelling. Steel tube having a longitudinal seam, inside and outside welds using a submerged arc welded.
