People often think that magnets absorb stainless steel screws, verify its pros and cons and authenticity, do not suck non-magnetic, think it is good, genuine; suckers have magnetic, it is counterfeit fake. In fact, this is a very one-sided, imprecise and erroneous method of identification. There are many kinds of stainless steel screws, 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. Martensite or ferrite type: such as 430, 420, 410, etc.;
stainless steel screw
The austenite type is either non-magnetic or weakly magnetic, and martensite or ferrite is magnetic.
The stainless steel that is usually used as a decorative tube plate is mostly an austenitic type 304 material. Generally speaking, it is non-magnetic or weakly magnetic. However, magnetic properties may occur due to chemical composition fluctuations or processing conditions due to smelting. However, stainless steel cannot be considered. The bolt is counterfeit or unqualified. What is the reason?
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 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 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.