After cold processing, the microstructure of 304 stainless steel coil will also transform into martensite. The greater the cold processing deformation, the more martensite transformation, and the greater the magnetic properties of the steel. Like a batch of steel strips, production Φ 76 tubes, no obvious magnetic induction, production Φ 9.5 Tube. Due to the large deformation caused by cold bending, the magnetic induction is more pronounced. The production of square rectangular tubes has a greater deformation than circular tubes, especially in the angled part, which causes more intense deformation and more pronounced magnetic induction.