Reasons and Solutions for Magnetism in Stainless Steel Castings

After the production of stainless steel castings is completed, if they are magnetized, it will cause the products to be unqualified. Therefore, in the process of processing and producing stainless steel castings, many details should be paid attention to to to avoid cooling and forming stainless steel castings with magnetism. The following will explain the reasons and solutions that cause stainless steel castings to have magnetism.

As is well known, austenitic stainless steel used in the production of stainless steel castings should not have magnetism, but some products produced have magnetism. Some manufacturers think it is due to the material, but after spectral testing, the material is qualified and there is no abnormality, which makes it difficult for many people to find the problem and solve it. After consulting a large amount of information and discussing with relevant technical personnel, we have made a new discovery that the reason why stainless steel castings formed by cooling have magnetism is because the internal structure of austenitic stainless steel changes during the cooling processing and forming process, and some austenite transforms into martensite, while martensitic stainless steel with a core structure has magnetism. So why does the austenite structure transform into the martensite structure?

Stainless steel can be divided into austenitic stainless steel, martensitic stainless steel, and ferritic stainless steel according to their structure. Austenitic stainless steel is a type of stainless steel that is widely used. In theory, austenitic stainless steel has no magnetism, but after cold processing, austenitic stainless steel will produce magnetism. According to some studies at home and abroad, the reason for the magnetism of austenitic stainless steel castings is that during the processing, when the stainless steel is heated above the austenite transformation temperature and maintained for a period of time, the stainless steel will transform into austenite. However, the stainless steel castings need to be cooled and formed. During the rapid cooling process, when the austenite cools down to the martensite transformation temperature, its structure begins to transform into martensite, and the transformation will only stop when the temperature drops below the martensite transformation temperature. When producing stainless steel castings, the stability, processing deformation, and processing methods of austenitic stainless steel may all affect its transformation into martensitic stainless steel.

Therefore, based on the causes and influencing factors of martensite formation, in order to avoid the occurrence of magnetism in stainless steel castings, it is necessary to choose austenitic stainless steel with high content of austenitizing elements when selecting raw materials. Solid heat fusion treatment can also be used to eliminate magnetism and work hardening phenomena* A "alloy demagnetizer" has emerged in the market recently that can eliminate the magnetism of stainless steel castings. It can transform the iron element in stainless steel castings into austenite, thereby achieving demagnetization. At the same time, the addition of alloy demagnetizer has good effects on the corrosion resistance and salt spray test of stainless steel castings.