Optimum efficiency control of high frequency welded pipe in welding process

Mechanism of high-frequency welding tube (erw steel pipe)are: tube voltage by the edge of the opening portion, so that the use of induced currents reach the meeting point. When current flows through the converging point of the metal is heated rapidly. Using pressure squeeze rollers, heat to melt the metal part reaches the hot extrusion bonding, and also will be out impurities from the weld. Technically, the low-frequency current through the resistive element, the impedance is mainly consumed. As frequency increases, the flux enhancer, a major factor in the impedance of the inductance, and increases as the frequency increases. During the welding process, as an induction coil primary winding, its size should be appropriately small. Power can be adjusted by the electromagnetic coupling, a high-frequency magnetic loss brought about with the number of turns and current.

Reason for the low frequency welding operation efficiency of an induction coil impedance and the location is not very good. When voltage is applied to the tube edge, a portion of the strip along the edge of the current flowing through the V-shaped strip edge heating zone; another part of the current from the inner surface of the tubular body opening flows through the outer surface of the return generated the power loss. It flows through the V-shaped area and the inner surface of the magnitude of the current depends on their impedance. Shorten the length of the V-shaped area and maintain their small distance can be reduced impedance of the path, and vice versa increased impedance and heat losses increase. Affect the length of the V-shaped area of the heating zone efficiency is greater than the impact frequency. Short working coil and a larger diameter tube can increase the impedance.

The effect is to obtain a large impedance, low impedance in the tube, so that more current is accumulated in the V-shaped region. Meanwhile, according to current work coil to concentrate the magnetic field so that the amount of current energy is concentrated on the tube V-shaped area. An important parameter is a magnetic impedance device, in use, should be selected as oscillatory magnetic flux density and high magnetic losses as low as possible magnet. But sometimes these requirements are incompatible, and therefore requires an operator to have a certain knowledge of the welding operation and the electromagnetic circuit design knowledge. Resistor placement is important. If they are too focused on the merging point below, although more efficient, but they are easily damaged. Therefore, the impedance is generally placed in the tube, so that the inner surface of the tube from a gap equivalent to the thickness of the pipe. Most small impedance unit installed at the bottom of the tube, this place is not only low welding efficiency, but also in the pipe to move easily towed away. Impedance of the magnetic induction coil center should be extended to the pinch point. The minimum length of the impedance of the induction coil diameter plus the length of the squeeze roller, a schematic diagram is set to + resistor. Some operators in the front end of the impedance as the best position, a large number of beads when welding, although prolonged resistor life, but the power consumption has increased.