Why is demagnetization required for spiral welded pipes? What is demagnetization?

Demagnetization, as its name implies, involves eliminating or reducing the magnetism of an object. The basic principle involves altering the arrangement of internal magnetic domains in magnetic materials through external actions (such as reverse magnetic fields, high temperatures, impacts, etc.), thereby weakening or eliminating the magnetism. In magnetic materials, there exist numerous tiny magnetic domains, and the magnetic moment directions of these domains are originally arranged in an orderly manner, causing the entire material to exhibit magnetism. When external actions disrupt this orderly arrangement, the magnetism of the material weakens or disappears.