How to Effectively Eliminate the Magnetism of Stainless Steel Castings
The stainless steel castings become magnetic when containing martensite, austenite or iron elements. But if the stainless steel is magnetic, it will affect its use. Today, let’s see how to effectively remove the magnetism of the casting.
1. Strictly control the equivalent chemical composition
In order to reduce costs, general manufacturers control the lower limit of Ni to between 8.0-8.2%. When Cr/Ni reaches a certain value, a certain amount of ferrite appears in the structure of the steel. While ferrite is magnetic. At this time, 1050 ~1080 solid solution treatment can completely dissolve ferrite into austenite, and then the stainless steel castings will not be magnetic.
2. Cold work hardening
The stainless steel castings will produce deformed martensite during cold working. The deformed martensite increases the strength of the stainless steel. However, the deformed martensite is magnetic. Solution treatment or even annealing can make the deformed martensite disappear, but the strength of the steel will decrease correspondingly.
3. If you want to ensure the strength of cold working, but also weak or even non-magnetic, you can use the following demagnetization methods:
According to the phase diagram principle, reduce the Cr/Ni value, especially increase the Ni and Mn content to the upper limit. Carried out the upper limit solution treatment before cold working, and control the grain size at 4 levels under the premise of ensuring the surface. This can reduce the magnetic properties after cold working. Generally, 304 stainless steel has a certain degree of weak magnetic properties after cold working. However, after beating or another impact, the austenite structure is transformed into martensite, which will have certain magnetic properties. And then heated to 1050 degrees, then water quenching thus can eliminate magnetism.
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