Stainless steel materials should be cold formed, but austenitic stainless steel is not magnetic, cold processed austenitic stainless steel will produce or strong or weak magnetic, especially the head this degree of processing larger products.This is because the basic structure of commonly used austenitic stainless steel is mostly metastable austenitic, so it is called metastable austenitic stainless steel.

　　When metastable austenitic stainless steel is cold-formed, part of austenite will undergo martensite transformation and maintain coherent with the original austenite. The non-diffusion phase change that occurs in a very short time by shearing is called Martensite transformation or deformation induced martensite transformation. The martensite in stainless steel generally has two forms of body-centered cubic structureα' martensitic and dense hexagonal structureε martensite, in which α'martensite is magnetic,εmartensite is non-magnetic, but only nickel-chromium When the content is higher, ε martensite is produced. Therefore, when a part of the structure of commonly used stainless steel is changed from austenite to martensite, it will produce magnetism.

　　The stability of austenite is determined by its chemical composition, and the martensite caused by processing is also related to the intensity of processing. For general purposes such as food, magnetism will not affect the use, so some standards at home and abroad are allowed to exist. For the manifestation of magnetism——ferrite content (ferrite is magnetic).

　　In the American ASME Standard Atomic Energy Volume (Volume Ш), when the operating temperature is <427℃, the ferrite content is allowed to be 3% to 7%; when the operating temperature is ≧427℃, the ferrite content is allowed to be ≧5% (the calculation method is WRC diagram). The recommended ferrite content in China's Volume 7 43 is 4% to 12% (Estimation method is Schaeffler phase diagram or Delong welding Organizational Chart). For nuclear equipment and special corrosive media used to receive neutron radiation, it is better to use materials or to do solution treatment.

　　According to this principle, our company's cold-processed stainless steel heads have no problems due to magnetic properties.