Residual magnetism causes and impact on quality of welding 

When the gas pipeline construction and repair welding operations, sometimes magnetic blow phenomena affect the welding process. Forming a magnetic blow is the result of the presence of residual magnetism in the pipe metal. Typically, the magnetic induction and magnetic remanence divided into two processes. Magnetic induction in plants often produce tube links, such as: metal smelting, using electromagnetic crane for loading and unloading, pipe parked or garaged in a strong magnetic field, the magnetization is completed nondestructive inspection method, the pipe is placed close to power lines and so strong. Processes often produce magnetic welding operations during the assembly and the use of a magnetic holder, fixture and took DC welding pipes, such as: prolonged contact is connected to a DC power supply electric wire, bare wire segment or short-circuit pipe welding clamp and so on. 
When welding with magnetic steel, often difficult to see the arc ignition, combustion undermine the stability of the arc, the arc of the deviation, the liquid metal and slag melt the spill from the weld pool in a magnetic field. In order to stabilize the welding process and improve the quality of the welded joint, the steel is magnetized to demagnetized before welding. It should be noted, to be welded steel pipe is difficult to achieve full demagnetization. Therefore, when the remanence is insufficient to affect the quality of welding, it allows welding. 

Magnetic elimination of carbon steel pipe process 
1 to determine the size and direction of the pipe left field; 
2 Select the degaussing method, system diagrams and technical means; 
3 butt welded steel pipe or at the degaussing degaussing with the selected method; 
4 After checking the amount of residual magnetism after degaussing, to see if it meets the requirements.