High-frequency Welding Process For LSAW Steel Pipe

1. Regulation of the status of high frequency induction coilThe useful heating time is long, and the high frequency induction coil should be as close as possible to the position of the squeeze roller. If the induction coil is far from the squeeze roller. The heat affected zone is wider and the weld strength is decreased; on the contrary, the edge of the lsaw steel pipe is insufficiently heated and the molding is poor after extrusion.

The cross-sectional area of??the impeder should be no less than 70% of the cross-sectional area of??the inner diameter of the steel pipe. The effect is to make the induction coil, the edge of the tube weld and the magnetic rod form an electromagnetic induction circuit. 5.5 The resistor is one or a set of special magnetic rods for the welded pipe.

The onset effect, the eddy heat is concentrated near the edge of the tube blank weld, heating the edge of the tube blank to the soldering temperature. The resistor is dragged in the tube blank with a wire, and the center position should be relatively fixed in the middle of the pressing roller. When starting up, because the tube billet is moving at a rapid speed, the resistor is damaged by the friction of the inner wall of the tube blank, and the demand is often changed.

The demand is cleared. The method of cleaning is to fix the tool on the frame. 5.6 Welds will occur after the weld is welded and squeezed. The welding rod is smoothed by the rapid movement of the welded pipe. The burrs inside the welded pipe are not generally cleared.

1. Weld gap controlAfter multiple rolls are rolled, the strip is fed into the welded pipe unit. The strip is gradually rolled up to form a circular tube blank with a gap of the opening, and the pressing amount of the pressing roller is adjusted, so that the gap of the weld is controlled at 1 to 3 mm and the ends of the welded joint are flush. If the gap is too large, the adjacent effect is reduced, the eddy current is lacking, and the weld crystals are directly combined and unfused or cracked. If the gap is too small, the adjacent effect will increase, the welding heat will be too large, and the weld will be burned. Perhaps the weld will be squeezed and rolled to form a deep pit, which will affect the appearance quality of the weld.
2. Welding temperature controlAccording to the formula (2), the welding temperature is mainly affected by the high-frequency eddy current thermal power. The high-frequency eddy current thermal power is mainly affected by the current frequency, and the eddy current thermal power is proportional to the square of the current excitation frequency; and the current excitation frequency is encouraged by the voltage., current and capacitance, inductance. The frequency formula is encouraged to be: f = 1 / [2? ( CL 1/2]... 1

Inductance = Flux / Current Where: f- Encouragement Frequency (Hz C- Encourage the capacitance in the loop (F Capacitance = Battery / Voltage; L- Encourage the inductance in the loop.

The frequency of encouragement is inversely proportional to the square of the capacitance and inductance of the excitation loop, and may be proportional to the square root of the voltage and current. The above equation is known. Simply change the capacitance, inductance or voltage and current in the circuit to change the size of the encouraged frequency, and then reach the target of the control welding temperature. For the low carbon steel, the welding temperature is controlled at 1250~1460 °C, and the wall thickness of the foot tube is 3~5mm. Welding penetration requirements. In addition, the soldering temperature can also be achieved by conditioning the soldering speed.

The edge of the heated weld does not reach the soldering temperature when the input heat is lacking. The metal structure is still solid, forming unfused or not welded; when there is a lack of heat input, the edge of the heated weld exceeds the soldering temperature, and the burnt or molten droplets are formed, causing the weld to form a melt.

4. Control of the pressing forceUnder the extrusion of the squeeze roll, the two edges of the tube blank are heated to the soldering temperature. The metal crystal grains that are formed together are saturated and crystallized, and finally constitute a strong weld bead. If the pressing force is too small, the number of crystals formed together will be small, the strength of the weld metal will decrease, and cracking will occur after the force is applied; if the pressing force is too large, the molten metal will be extruded out of the weld, not only reducing The weld strength is strong, and many burrs in the surface occur, and even defects such as weld seams are formed.

A worker from a steel pipe company, which is located in China.