2024-11-22
Stainless steel-Magnetic Effects of Stainless Steels
Wrought, austenitic stainless steels, such as 304 and 316, are generally regarded as non-magnetic in the annealed condition, i.e. they are not attracted significantly by a magnet. However, if they are cold worked they will be attracted to a permanent magnet. The change occurs because the cold work deformation induces a transformation of the microstructure from austenite to martensite. The effect is less marked in alloys with high concentrations of austenite stabilisers such as nickel, nitrogen and carbon. Once the martensite is formed, it may also become magnetised sufficiently to pick-up light objects such as paper clips.Magnetic attraction effects are most often noticed in heavily cold worked fabrications such as wire or the dished end of a pressure vessel. It is possible to remove the magnetic effects by solution annealing and water quenching but this will also reduce the tensile properties and may give rise to distortion.