How to distinguish jack true and false

There are many kinds of jacks, which can be divided into several types according to the organizational structure at room temperature:
1. Austenitic type: such as 304, 321, 316, 310, etc.;
2. Martensitic or ferritic type: such as 430, 420, 410, etc.;

The austenite type is either non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. The jacks usually used as decorative tube plates are mostly austenitic type 304 materials. Generally, they are non-magnetic or weakly magnetic. However, magnetic properties may occur due to fluctuations in chemical composition or processing conditions due to smelting. However, this cannot be considered as Counterfeit or unqualified, what is the reason?

As mentioned above, austenite is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Due to segregation or improper heat treatment during smelting, a small amount of martensite or ferrite in the austenitic 304 jack can be caused. Body organization. In this way, the 304 jack will have weak magnetic properties. In addition, after the 304 jacks are cold-worked, the microstructure will also transform into martensite. The greater the degree of cold deformation, the more martensite transformation and the greater the magnetic properties of the steel. Such as the same batch of steel, production Φ76 tube, no significant sense of magnetic, production Φ9.5 tube. Due to the large bending deformation of the magnetic induction is obvious, the production of rectangular tube due to the deformation of the larger than the round tube, especially the folding part, the deformation is more intense magnetic more obvious.

In order to completely eliminate the magnetic properties of 304 steel caused by the above reasons, the stable austenite structure can be recovered by high-temperature solution treatment, thereby eliminating magnetic properties. In particular, the magnetism of the 304 jack due to the above reasons is not the same as that of the jacks of other materials such as 430 and carbon steel, which means that the magnetism of the 304 steel always shows weak magnetism.

This tells us that if the jack is weakly magnetic or completely magnetic, it should be judged to be 304 or 316; if it is magnetic like carbon steel, it shows strong magnetism, because it is not 304 material.

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