First, the two sides of straight seam steel pipe billet heated to the welding temperature, the extrusion roller squeeze, forming a separate metal grains mutual penetration, crystallization, the ultimate form a solid weld. If the extrusion pressure is too small, the number of individual crystals is small, the strength of the weld metal will drop, and cracking will occur after being forced. If the extrusion force is too large, the molten metal will be extruded out of the weld, high weld strength, and will attack a small amount of internal and external burr, as well as the formation of welding joints and other defects.
Second, straight seam high-frequency induction coil should be as close as possible squeeze roller position. If the induction ring is far away from the squeeze roller, the invalid heating time is longer, the heat affected zone is wider and the weld strength is decreased; on the contrary, the edge of the weld is lack of heating and the molding is poor after extrusion.
Third, the strip into the welded pipe unit, the multi-roll rolling, the strip gradually rolled up to form a circular tube with a tooth gap, adjust the reduction of the squeeze roll, the weld gap to master in the 1 ~ 3mm, and make both ends of the weld flush.
Fourthly, the welding temperature of straight seam steel pipe is mainly affected by the high-frequency eddy current thermal power. According to the formula, the secondary frequency of the high-frequency eddy current is influenced by the frequency of the current. The eddy current heating power is proportional to the square of the current excitation frequency. Also by the encouragement of voltage, current and capacitance, inductance.
