The harm of magnetic field during welding of spiral steel pipe

 In recent years, with the continuous development of the current society, spiral steel pipes are used in many industries or projects. They can be used as pipelines for conveying fluids, such as oil, natural gas, gas, water and some In the process of pipelines for solid materials. For spiral steel pipe manufacturers often need to perform welding and other work during use, what I want to share here today is the harm of magnetic field when spiral steel pipe manufacturers are welding.

     Generally, in the welding process of spiral steel pipe manufacturers, the internal welding adopts the direct current welding method, and the large internal welding wire and the welding head will generally generate a strong magnetic field due to the phenomenon of large current, and for the steel pipe body Under the action of this magnetic field, the magnetic moment obtains or tends to obtain an arrangement in the same direction as the external magnetic field. Therefore, when the welding is over, the magnetic field gradually decreases until it disappears, due to the hysteresis phenomenon, there is a residual magnetic flux density on the tube body, which is what we usually call the remanence phenomenon. The influence of remanence is particularly prominent. Regarding the existence of residual magnetism, generally, the arc phenomenon will occur when the pipeline is welded butt, which will affect the welding quality. The existence of residual magnetism seriously affected the construction quality.

     Therefore, if we want to eliminate the magnetic field, we need to point the arc to the side of the pipe groove edge with the secondary output cable of the DC arc welder to loop 3-5 turns in a certain direction, and the cable short circuit forms a loop; the adjustment of the welding current knob is From small to large, change from large to small instantaneously, and do demagnetization treatment.

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