How to remove the magnetism of 304 stainless steel castings
1. Chemical composition equivalent composition control
In order to save costs, general manufacturers control the lower limit of Ni to between 8.0-8.2%. When Cr/Ni reaches the value, ferrite appears in the steel structure, and ferrite is magnetic; at this time, 1050~1080℃ solidification is used. The solution treatment can dissolve ferrite into austenite and it will not be magnetic.
2. Cold work hardening
When austenitic stainless steel produces deformed martensite during cold working, the deformed martensite increases the strength of the stainless steel, and the deformed martensite is magnetic. Either solution treatment or annealing can make the deformed martensite disappear, but the strength of the steel will decrease.
If you want to maintain the cold working strength, but also weak or non-magnetic, you can use the following demagnetization methods:
1. According to the principle of phase diagram, reduce the value of Cr/Ni and increase the content of Ni and Mn. The upper limit solution treatment is carried out before cold working, so that the grain size can be controlled at 4 levels under the premise of the surface; it can reduce the magnetic properties after cold working.
2. Generally, 304 has weak magnetic properties after cold working. After beating or other impact, the austenite structure is transformed into martensite, which will become magnetic at this time. Heating to 1050 degrees, then water quenching, can remove the magnetism.