If stainless steel castings are magnetized after production, it can lead to unqualified products. Therefore, in the process of processing and producing stainless steel castings, attention should be paid to many details to avoid cooling and forming stainless steel castings with magnetism. Below, we 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 believe that it is due to the material, but after spectral testing, the material is qualified and there are no abnormalities, making it difficult for many people to find the problem and unable to solve it. After consulting a large amount of information and discussing with relevant technical personnel, we have found that the reason why cooled stainless steel castings have magnetism is because the internal structure of austenitic stainless steel has changed during the cooling and processing process, some austenite has transformed into martensite, while martensitic stainless steel with a core structure has magnetism. So why does the austenite structure transform into a martensitic 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 commonly used type of stainless steel. Austenitic structured stainless steel theoretically has no magnetism, but after cold processing, austenitic stainless steel will produce magnetism. According to some domestic and foreign studies, the reason why austenitic stainless steel castings have magnetism is that during the processing, when the stainless steel is heated above the austenite transformation temperature and maintained for a period of time, it will transform into austenite. However, the stainless steel castings need to be cooled and formed later. In the rapid cooling process, when the austenite cools down to the martensite transformation temperature, its structure begins to transform into martensite, and the transformation stops only 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 magnetic properties 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 demagnetizing agent" has emerged in the recent market that can eliminate the magnetism of stainless steel castings. It can transform the iron element in stainless steel castings into austenite, thereby achieving the purpose of demagnetization. At the same time, the addition of alloy demagnetizing agent has good effects on the corrosion resistance and salt spray test of stainless steel castings.