n the spiral steel tube feeding unit, the multi-roll strip is gradually rolled up to form an open pipe gap. The extrusion roll is reduced and adjusted. The weld gap is controlled at 1-3 mm, and the end of the weld is even.
1. If the gap is too large, the proximity effect decreases and the eddy current lacks heat, the indirect disadvantage of welding crystal bonding is due to the lack of fusion or cracking.
2. The small gap will increase the proximity effect, increase the welding heat, and cause welding combustion. After welding or extrusion, it will be rolled after pit formation, which will affect the surface quality of the weld.


After the two edges of the tube are heated to the welding temperature, common metal particles penetrate and crystallize into each other during the extrusion of the extrusion roll, and finally form a strong weld. If the extrusion pressure of pipe is too small and the number of common crystals is very small, the strength of weld metal will be reduced because of the stress and cracks will occur; if the pressure is too large, the molten metal will be extruded and welded, which will not only reduce the welding strength, but also produce a large number of internal and external burrs, and even cause defects such as welding seam.