During the high frequency welding process, the welding technology, quality control process parameters, the impedance of the induction coil and the position of the placement has significant influence on the ERW steel pipe quality.
1. Control the steel pipe weld gap
If the weld gap is too much, it might increase the possibility of weld seam cracks. If the weld gas is too small, it will cause weld burning, molten metal splashes due to the excessive heat. It will affecting the quality of welding seam in the end.
2. The position of the high frequency induction loop
Induction loop should be placed in the same center line with the steel pipe. The distance between induction loop and the squeeeze roll end should be controled close enough without burning squeeze rollers premise. If the induction loop from the squeeze roll farther, the effective heating time will be longer and the heat affected zone will be wider. This will cause the strength of the steel pipe weld penetration or decrease. On the contrary, the induction coil will burned the squeeze rollers easily.
3. The location of resistor
Impedance is one or a group welded dedicated magnet impedance the cross sectional area which is usually not less than 70% of the inner cross section area of the pipe. Its role is to form a magnetic induction lood between the induction ring and tube seam edge of the magnet. Therefore, it will generate proximity effect, the vortex heat concentrated in the vicinity of the pipe weld the edges, and the edge of the pipe is heated to welding temperature. Resistor should be placed in the V-shaped area of the heating section and the tip at a position squeeze roll center to tube center line and the center line of the same. An impedance position placed well, affect the welding speed and welding quality welded pipe, steel pipe cracks.
4. High frequency welding parameters
Control high frequency power input to the Pipe Weld heat input of heat called heat input. When converting electrical energy into heat, the heat input to the formula: Q = KI2 Rt (1) of the formula Q- tube by heat input; - K-energy conversion efficiency; the I-welding current; the R- loop impedance; T- heating time. Heating time: t = Lv (2) center where L- induction coil or electrode at the tip to squeeze roll distance; v- welding speed.
