High frequency (stable and continuous) power, welding speed, welding extrusion force and opening V angle are the most important process parameters, which must be matched reasonably, otherwise the welding quality will be affected.
If the welding speed is too high or too low, it will lead to low temperature welding impermeability and high temperature overburning, and the weld will crack after flattening.
When the extrusion force is insufficient, the edge metal to be welded can not be completely pressed together, the residual impurities in the weld are not easy to discharge, and the strength is reduced. When the extrusion force is too large, the metal flow angle increases, the residue is easy to be discharged, the heat affected zone becomes narrow, and the welding quality is improved. However, if the pressure is too high, it will cause large sparks and splashes, resulting in the extrusion of molten oxide and part of the metal plastic layer, and thinning of the weld after scratch, thus reducing the strength of the weld. Proper extrusion force is an important prerequisite to ensure welding quality.
If the opening angle is too large, the high frequency proximity effect is reduced, the power loss is increased and the welding temperature is reduced. If the welding speed is constant, the penetration will be poor; if the opening angle is too small, the welding current will be unstable, and small spatter will occur at the extrusion point.
Induction coil is an important part of high frequency welded pipe production. The gap between induction coil and billet and the width of opening have great influence on welding quality.
The gap between the induction coil and the tube blank is too large, which leads to the sharp decline of the inductance efficiency;
If the gap between the induction coil and the tube blank is too small, it is easy to generate discharge between the coil and the tube blank, and it is also easy to be damaged by the moving tube blank.
If the width of the induction coil is too large, the welding temperature of the butt edge of the tube blank will be reduced. If the welding speed is fast, it is easy to produce false welding and cracking after straightening.
