Types of stainless steel

There are many kinds of stainless steel, which can be divided into several categories according to the organizational structure at room temperature:

1. Austenitic type: such as 304, 321, 316, 310, etc.;

2. Martensite or ferrite type: such as 430, 420, 410, etc.;

The austenitic type is non-magnetic or weakly magnetic, and the martensite or ferrite is magnetic.

As mentioned above, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetized. Because of chemical segregation or wrong heat treatment during smelting, a small amount of martensite or iron in austenitic 304 stainless steel will result. body structure. In this way, 304 stainless steel will carry weak magnets.

In addition, 304 stainless steel undergoes cold working, and the organizational structure will also transform to martensite. The greater the degree of cold working deformation, the more martensite transformation, and the larger the magnet of the steel. Like a batch of steel strips, Φ76 pipes are manufactured without significant magnetic induction, and Φ9.5 pipes are manufactured. The magnetic induction is more pronounced because the bending deformation is too large, and the deformation of the square rectangular tube is larger than that of the round tube, especially in the case of the corners, the deformation of the stronger magnet is more significant.

To completely eliminate the magnets of 304 steel caused by the above reasons, high temperature solid solution can be used to repair the stable austenite structure, thus eliminating the magnets.

In particular, it should be clearly pointed out that the magnets of 304 stainless steel caused by the above reasons are not at the same level as the other materials of stainless steel, such as 430 and carbon steel magnets. In other words, the magnets of 304 steel still show weak magnets. .