Principle of high frequency welding finned tube
The basis of high-frequency welding is to use the two major effects of high-frequency current: skin effect and proximity effect. With the help of the skin effect of high-frequency current, high-frequency electric energy can be concentrated on the surface of the workpiece, and the proximity effect can be controlled. The location and range of high-frequency current flow. When the high-frequency current is required to be concentrated on a certain part of the workpiece, under the action of the skin effect and the proximity effect, the metal ends of the adjacent two sides will be quickly heated to the melting or welding temperature, and then under the action of external pressure, The two parts can be firmly welded into one body.
The welding process of high-frequency welding finned tubes is shown in Figure 1. The steel strip is evenly and steadily wound on the surface of the steel pipe according to a certain pitch. At the same time, the high-frequency current is used as the welding heat source to locally heat the contact surface and waiting area of the steel pipe and the steel strip. Welding area, make it melt and weldable state, weld firmly under the application of external force. During the welding process of the spiral fin tube, the steel strip is thin and the current is concentrated, which can easily reach the welding temperature, while the steel tube is thicker and the current is scattered, which is not easy to concentrate. The temperature of the steel tube is often lower than the temperature of the steel strip, which affects the welding quality. If the temperature of the steel pipe is increased by increasing the power of the power supply, the heating temperature of the steel belt is often too high and it is broken, and the surface temperature of the steel pipe is not enough. Therefore, it is very important to adjust the current distribution of the two and select the appropriate welding parameters. In addition, the high-frequency welding power supplies produced in my country are all high-frequency welding power supplies, and there is no special high-frequency power supply for fin tube welding. Because the impedance of fin tube welding is larger than that of steel pipe welding, there is a mismatch between the power supply and the load. The problem is that only proper matching can increase the output power and prevent energy from being consumed by “short-circuiting”. Therefore, improving the characteristics of the high-frequency welding power source and obtaining the best matching of the power source are the prerequisites for ensuring the welding quality of the fin tube.