Magnetism is not good for stainless steel castings, which will affect the quality of our products to some extent. So what caused its magnetism and how can we solve it? It will be covered in the following article.
1. Chemical equivalent composition control is not in place
In order to reduce the cost, the general stainless steel casting manufacturers control the lower limit of Ni, between 8.0 and 8.2%. When Cr/Ni reaches a certain value, a certain amount of ferrite appears in the tissue, and ferrite is magnetic. At this point, the 1050 ~ 1080 ℃ solution treatment can remove the magnetism of stainless steel castings when it is completely into the austenite.
2. Cold Processing
When austenite stainless steel deforms martensite during cold processing, the deformable martensite will increase the strength of stainless steel, while the deformable martensite is magnetic. Solid solution treatment and even annealing can make the deformation martensite disappear, but the strength of the steel will decline.
If you want to guarantee the strength of cold processing, meanwhile weaken magnetism or even no magnetism, you can use the following demagnetization method:
1. According to the phase diagram principle, reduce Cr/Ni value, especially increase the content of Ni and Mn to the upper limit. Before cold processing, upper limit solid solution treatment should be performed to control grain size 4 on the premise of guaranteeing the surface. Can reduce the magnetic after cold processing.
2. Generally 304 stainless steel castings after cold processing have certain weak magnetism. When the austenite tissue is transformed into a martensite by a knock or other impact, there is a certain amount of magnetism. Heat to 1050 degrees and water quench to remove the magnetism.