welding gap of carbon welding steel pipe

In practical application, how do you handle the welding gap of carbon welding steel pipe? Today, we will do a detailed introduction for you and help you handle this problem. The strip steel is transferred into the welded pipe device. Through multi times rolling, strip steel is rolled up gradually and formed round billet with an open space. Adjust the rolling reduction of the squeezing roller; make the welding gap controlled in 1-3mm and the joint match on both ends. If the gap is too large, it will result in decrease of proximity effect, insufficient eddy heating, bad welding gap joint to occur incomplete or crack. Conversely, the proximity effect increase, high welding heat will cause the burning of the welding gap; or welding forms the deep pit by extrusion and rolling, which will affect surface quality of welding. Following four tips will help you deal with these problems.
Welding temperature is mainly influenced by high frequency eddy thermal power. According to the formula, high frequency eddy thermal power is impacted by the current frequency. Eddy thermal power and current frequency is the proportional to the square. However, current frequency is affected by excitation voltage, current, capacitance and inductance. For low carbon steel, welding temperature is controlled in 1250-1460℃ which can meet the 3-5mm penetration requirements of wall thickness. Furthermore, welding temperature is achieved by adjusting welding speed.
When two edges of pipe billet are heating to the welding temperature, the two edges will form a common metal grain through interpenetrate and crystallization under the extrusion of squeezing roller to form solid weld eventually. If with small extrusion pressure, the amount of common crystal is small, the strength of welded metal will drop, this leads to cracking after stress. While with large extrusion pressure, the molten metal will be squeezed out of the seam. This not only reduces the weld strength, but also can produce a mass of inside and outside burrs and even cause the welding seam defects etc.
High frequency induction coil should be close to the squeeze roller as far as possible. If induction coil is far away from the squeezing roller, the effective heating time is longer and heat affected area is broad, the welding strength will decrease. Conversely, if the weld edge is lack of heating, the molding is bad after extrusion.


The weld seam can produce welding scar that need to be cleared after welding and extrusion. The removing method is to fix the cutter on the rack through the rapid movement of welded pipe to slick the welding scar.