The strength of the proximity effect is related to the following three factors:
The closer the adjacent distance between two conductors, the stronger the proximity effect, especially when the distance between the two conductors is close to or tends to zero, the current in the conductors almost all converge to the adjacent layer, making the adjacent surface The sharp increase of the current on the surface causes heating of adjacent surfaces, such as converging to the position of the extrusion point, which is of great significance for the formulation of the high-frequency welded pipe process. The closer to the apex of the V angle of the opening, the closer the distance between the two edges of the strip, and therefore the proximity The stronger the effect, the higher the strip edge temperature, until it is close to the melting point of the metal, and the welding is realized under the squeezing force of the subsequent squeeze roll. Therefore, the proximity effect requires that the welded pipe process needs to pay attention to the size of the V-shaped opening. Welding heat, speed and quality are related.
The strength of the proximity effect is closely related to the ratio of half the thickness of the conductor to the current penetration. The larger the ratio, the stronger the proximity effect. On the contrary, the smaller the ratio, the weaker the proximity effect. See the formula: ratio = conductor thickness/2 penetration degree.
The higher the current frequency, the stronger the proximity effect based on the skin effect. The significance of the proximity effect on the production of high-frequency longitudinal welded pipes.
The significance of the proximity effect is that it can control the flow path, position and range of the high-frequency current, guide the production of welded pipes, and formulate the welding process. For welded pipes of different specifications, such as the production of large-diameter thick-walled pipes, the corresponding frequency and opening need to be selected. After considering the skin effect, the current frequency needs to be appropriately reduced. By reducing the opening angle, the distance between the two edges of the blank to be welded and the current flow path are shortened, thereby shortening the heating time and increasing Improved welding efficiency.
On the other hand, because the high-frequency current of the induction coil and the induced current on the tube to be welded are both high-frequency currents, there is also a proximity effect between them. If they are placed symmetrically, the current on the tube to be welded will be evenly distributed. If placed asymmetrically, the current on the tube blank to be welded will be unevenly distributed. Therefore, specifically, the gap between the induction coil and the tube blank to be welded should be installed in a small top-down manner, so that the The edges of the billet to be welded collect more current. At the same time, in order to strengthen the proximity effect, the gap between the inner diameter of the induction coil and the outer diameter of the tube to be welded should be minimized within the range allowed by the process.
Tips:ASTM A53 ERW steel pipe is a typical carbon steel pipe. It is largely used to convey fluids at low / medium pressures such as oil, gas, steam, water, air and also for mechanical applications.