The heat treatment of welded components usually involves heating the entire component in a furnace. For large-scale welded components, a huge heat treatment furnace is required, which consumes a lot of energy, and is difficult to load, unload, and transport. Sometimes, during the heating process, Deformation, especially of thin-walled containers, is often uncorrectable. Therefore, it is difficult to use overall heating for the heat treatment of welds of large thin-walled containers. Only local heating of the welds of the container is a more effective and economical method.
1. Power frequency induction heating annealing of steel container welds
Containers made of 25CrMnSiA steel require annealing of the welds after butt welding. The diameter of the container is 654mm and the wall thickness is 8mm. The power frequency inductor used has a magnetic conductor, and the coil is wound with pure copper tube. This inductor heats the welding seam of the container to 750 - 800°C in 8 minutes, with a voltage of 380V, a current of 350A, and a power of 28KW.
2. Power frequency induction heating and tempering of brass container welds
Since the brass container is a non-magnetic material, the efficiency and power factor of power frequency induction heating are low and the heating speed is slow. Therefore, when the weld of the brass container is tempered by power frequency induction heating, there is a gap between the induction coil and the weld metal. Put a steel plate in between. When electric induction heating is applied, the brass container and the steel plate are heated at the same time. Since the steel plate is magnetic, the heating speed is higher than that of brass. Therefore, in addition to the induction heating itself, the brass container also has heat conducted by the steel plate, thereby improving the heating at the weld. speed. The coil of the sensor can be wound around the outside of the weld with a cable wrapped in a rubber tube, and water can be used to cool it when it is heated by electricity. Since the width of the weld that requires tempering is not large and the number of coil turns is small, a low-voltage, high-current transformer is required for power supply.。
3. Medium frequency induction heating annealing of cylinder welds
The two parts of a cylinder containing liquefied petroleum gas are butt-welded together after being pressed and formed. Since they have to withstand greater pressure, the welds are required to be annealed. Figure 12-92 shows the medium frequency induction heating and annealing equipment for the welds of LPG cylinders. The induction coil is 1 turn, connected to the medium frequency step-down transformer, and is annealed by periodic induction heating. Since LPG cylinder manufacturers adopt different production processes, some manufacturers only anneal the butt welds of the cylinders, while others require the entire cylinder to be annealed. Figure 12-93 shows the medium frequency induction heating annealing equipment for cylinders. The cylinders are heated by sequential induction, that is, a cylinder is pushed in at the feed end, and a heated cylinder is pushed out at the discharge end.
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GS-ZP-1200
