In the construction and repair of gas pipeline welding operations, sometimes magnetic blow phenomena affect the welding process.

The formation of magnetic blow pipe metal present in remanence results. Typically, the remanence is divided into two kinds of induction magnetic and processes magnetic. Often produce magnetic induction pipe part in the factory, such as: metal smelting, using electromagnetic crane for loading and unloading, pipe parked in a strong magnetic field, the magnetization method with complete nondestructive inspection, pipe placed close to power lines and so powerful. Magnetic assembly processes often produce during welding operations and the use of a magnetic holder, clamps and pipe welding with DC, such as: prolonged contact with the DC power supply connected to electrical conductors, bare wire welding clamp and pipe segment or short-circuit and so on.

When the welding magnetic seamless steel pipe, often can see the difficulties of arc ignition, arc burning stability of destruction, in the field of arc deviation, the liquid metal and slag melting body in the welding pool spatter. In order to stable welding process and improve the quality of welding joint, the magnetized steel pipe need to be degaussing before welding. It should be points out that it is difficult to achieve complete demagnetization for welded steel pipe.

So, when the remanence is insufficient to influence welding quality, and allows for welding.