High-frequency welded pipe is a steel pipe that uses the skin effect and adjacent effect generated by high-frequency current to connect steel plates. The emergence and maturity of high-frequency welding technology is a key process in the production of ERW pipe. The quality of high-frequency welding directly affects the overall strength, quality level and production speed of welded pipe products.
The basic principle of high frequency welded pipe welding
The so-called high frequency is relative to the AC current frequency of 50Hz, and generally refers to the high frequency current of 50KHz~400KHz. When high-frequency current passes through a metal conductor, two peculiar effects will be produced: skin effect and proximity effect. High-frequency welding uses these two effects to weld steel pipes. So, what are these two effects?
1. Skin effect
It means that when an alternating current of a certain frequency passes through the same conductor, the current density is not evenly distributed in all cross-sections of the conductor. It will mainly concentrate on the surface of the conductor, that is, the density of the current on the surface of the conductor is high, and the density inside the conductor is small, so we vividly call it: "skin effect". The skin effect is usually measured by the penetration depth of the current, the smaller the penetration depth value, the more significant the skin effect. This penetration depth is proportional to the square root of the conductor's resistivity and inversely proportional to the square root of frequency and permeability. In layman's terms, the higher the frequency, the more concentrated the current is on the surface of the steel plate; the lower the frequency, the more dispersed the surface current is. It must be noted that although steel is a conductor, its magnetic permeability will decrease as the temperature rises, that is to say, when the temperature of the steel plate rises, the magnetic permeability will decrease and the skin effect will decrease.
2. Proximity effect
It means that when the high-frequency current flows in opposite directions in two adjacent conductors, the current will flow concentratedly to the adjacent edges of the two conductors. Even if the two conductors have a shorter side, the current does not flow along the shorter route. We call this effect: "proximity effect".
The proximity effect is essentially due to the effect of inductive reactance, which plays a dominant role in high-frequency currents. The proximity effect increases as the frequency increases and the distance between adjacent conductors becomes closer. If a magnetic core is added around the adjacent conductor, the high-frequency current will be more concentrated on the surface of the workpiece.
These two effects are the basis for realizing metal high-frequency welding. High-frequency welding uses the skin effect to concentrate the energy of high-frequency current on the surface of the workpiece; and uses the proximity effect to control the position and range of the high-frequency current flow route. The speed of the current is very fast, it can heat and melt the edges of the adjacent steel plates in a short time, and realize the butt joint by extrusion.
The basic principle of high frequency welded pipe welding
The so-called high frequency is relative to the AC current frequency of 50Hz, and generally refers to the high frequency current of 50KHz~400KHz. When high-frequency current passes through a metal conductor, two peculiar effects will be produced: skin effect and proximity effect. High-frequency welding uses these two effects to weld steel pipes. So, what are these two effects?
1. Skin effect
It means that when an alternating current of a certain frequency passes through the same conductor, the current density is not evenly distributed in all cross-sections of the conductor. It will mainly concentrate on the surface of the conductor, that is, the density of the current on the surface of the conductor is high, and the density inside the conductor is small, so we vividly call it: "skin effect". The skin effect is usually measured by the penetration depth of the current, the smaller the penetration depth value, the more significant the skin effect. This penetration depth is proportional to the square root of the conductor's resistivity and inversely proportional to the square root of frequency and permeability. In layman's terms, the higher the frequency, the more concentrated the current is on the surface of the steel plate; the lower the frequency, the more dispersed the surface current is. It must be noted that although steel is a conductor, its magnetic permeability will decrease as the temperature rises, that is to say, when the temperature of the steel plate rises, the magnetic permeability will decrease and the skin effect will decrease.
2. Proximity effect
It means that when the high-frequency current flows in opposite directions in two adjacent conductors, the current will flow concentratedly to the adjacent edges of the two conductors. Even if the two conductors have a shorter side, the current does not flow along the shorter route. We call this effect: "proximity effect".
The proximity effect is essentially due to the effect of inductive reactance, which plays a dominant role in high-frequency currents. The proximity effect increases as the frequency increases and the distance between adjacent conductors becomes closer. If a magnetic core is added around the adjacent conductor, the high-frequency current will be more concentrated on the surface of the workpiece.
These two effects are the basis for realizing metal high-frequency welding. High-frequency welding uses the skin effect to concentrate the energy of high-frequency current on the surface of the workpiece; and uses the proximity effect to control the position and range of the high-frequency current flow route. The speed of the current is very fast, it can heat and melt the edges of the adjacent steel plates in a short time, and realize the butt joint by extrusion.
