Why is stainless steel magnetic?

- Apr 11, 2018-

Why is stainless steel magnetic?


People often think that magnets absorb stainless steel, verify its pros and cons and authenticity, do not absorb non-magnetic, think it is good, genuine; suckers have magnetic, it is considered fake counterfeit goods. In fact, this is a very one-sided, imprecise and erroneous method of identification.
A wide variety of stainless steels can be divided into several types according to the organizational structure at room temperature: welding overlay


1, austenitic type: such as 201,202,301,304,316, etc.;

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

3, austenite type is non-magnetic or weak magnetic, martensite or ferrite is magnetic.


The most commonly used stainless steel for decorative tube sheets is austenitic type 304. Generally speaking, it is 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? pipe fittings


The above mentioned austenite is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Due to segregation or improper heat treatment during smelting, it will cause a small amount of martensite or ferrite in austenitic 304 stainless steel. Body organization. In this way, 304 stainless steel will have a weak magnetic.

In addition, 304 stainless steel after cold processing, the organization structure will also be transformed to martensite, the greater the cold deformation degree, the more martensite transformation, the greater the magnetic 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 folded part, the deformation is more intense magnetic more obvious. SLIP ON FLANGE


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 magnetic properties of 304 stainless steel due to the above reasons are not the same as the magnetic properties of stainless steels of other materials such as 430 and carbon steel. That is, the magnetic properties of 304 steel always show weak magnetic properties. This tells us that if stainless steel is weakly magnetic or completely magnetic, it should be judged to be 304 or 316; if it is the same as carbon steel, it shows strong magnetism, because it is not 304 material.