1. Pipeline clearance control
Adjust the extrusion quantity of the extrusion roll to keep both ends of the weld seam level, and control the gap of the weld seam below 7 degrees to 1-3 mm. Excessive weld control may lead to poor welding, non-melting or cracking of the weld, and too small weld control. Due to excessive heat, it is easy to cause weld burns, metal melting and excessive melting, which will affect the welding quality (metal spatter causes: extruding the edge of the melted pipe, the weld in the vapor pressure is larger than the surface pressure).


2. Position Control of High Frequency Induction Coil
The position of induction coil should be on the same central line with the steel pipe. The distance between the front end of induction ring and the central line of pressing roll should be as close as possible to the steel pipe, otherwise the strength of weld will be reduced. The coupling of induction coils is as thin as possible. When cotton rolls are used, the width of the induction ring should be equal to the diameter of the pipe. The choice of single or double loops has a great influence on the frequency and output efficiency of high frequency oscillation.


3. Position control of resistors (also known as magnets)
Resistors are a group or special magnetic rods whose cross-sectional area accounts for 70% of the cross-sectional area of pipelines. Its function is to strengthen electromagnetic induction and concentrate eddy current heat on welding edge. Sometimes magnetic rods are added to the weld seam to support it.  The temperature of the magnetic rod has a great influence on the permeability. The higher the temperature, the lower the permeability. The magnetic rod should be placed in the heating part of V zone, in front of the center of extrusion roll. The position of magnetic pole and permeability directly affect the welding efficiency and quality.


4. Output heat control
The heat input from high frequency power supply to the welded part of steel pipe is called input heat. The input heat is insufficient, the welding speed is too fast, the edge of the pipe body can not reach the welding temperature, forming non-welding or non-penetrating cracks, but the input heat is too large, the welding speed is too slow, it is easy to burn excessively, so that the welding seam breaks down, resulting in metal spatter and formation. Stomata. By adjusting the high frequency voltage or welding speed to control the input heat, the weld seam of steel pipe will not appear non-penetrating and non-welding phenomenon, and meet the welding quality requirements.


In short, the production process of high frequency welded pipe is a special process, each link is more important. Strict control will play a great role in welding quality and energy efficiency.