Why Are Stainless Steel Screws Magnetic?

There are many kinds of fastener manufacturing materials, among which stainless steel fasteners have better performance in appearance and strength, and have the advantages of corrosion resistance, easy manufacturing, and good welding.

However, in the public’s cognition of stainless steel fasteners, stainless steel fasteners should not be magnetic, and even the use of magnet adsorption to check the authenticity of stainless steel fasteners, if only there is no magnetism to judge the authenticity of stainless steel fasteners is unscientific, but also a wrong concept.

Any austenitic stainless steel material is not magnetic before processing. Still, the stress generated during high-speed cold punching equipment’s instantaneous extrusion molding process is the main reason for the slightly magnetic finished product. This is also why the magnetic properties of the screw are higher than those of the nut because the head of the screw changes much more.

As a professional fastener company, Xinchi is pleased to introduce the specific reasons why stainless steel screws are magnetic.

Processing reasons

Austenitic stainless steel and the raw material itself are not magnetic, but the raw material makes the product slightly magnetic due to stress during cold processing.

When the raw material like the disk comes out, if it is austenitic stainless steel, it is not magnetic when detected by ordinary magnets. Still, if it is ferrite and martensite, it is certainly magnetic. In the process of cold processing of austenitic stainless steel, it will have a part of the grain structure, it will precipitation a part of the ferrite and martensite, at this time it will show certain weak magnetic characteristics, but its material is still austenitic, for example, like authentic 304 and 316. Therefore, we can no longer use whether it is magnetic to judge whether it is authentic stainless steel.

Product deformation

The magnetic properties shown by different similar products are different due to factors such as the amount of deformation, and similar products will be different because of the size of the specifications, even if the same product will be slightly different because of different parts and magnetic properties, these performances can explain the magnetic differences caused by stress.

In the process of processing the same material, when its material deformation is relatively small, its magnetism will be relatively weak, and when the deformation is relatively large, its magnetism will be relatively large in the place where the deformation is large. Therefore, the same 304 material when we go to measure its screw magnetism will be greater than the nut magnetism, this is because it in the processing process, the deformation process caused by the change of grain structure and some stress concentration changes will lead to it having a certain magnetic. For example, like the tooth shape above, the deformation of the tooth type of the self-tapping teeth is larger than that of the mechanical teeth, so the magnetism of the self-tapping screws is usually greater than that of the mechanical teeth.

Tips to determine whether it is authentic stainless steel

In fact, if you want to use magnetism to determine whether it is authentic stainless steel, there will be a big misunderstanding, what is it? Now in fact, people who specialize in stainless steel know that there is a material on the market called general material, this material is completely non-magnetic, called non-magnetic nickel, but it is fake stainless steel or low nickel stainless steel, it is not magnetic, but compared with austenitic stainless steel, its anti-corrosion performance is very poor. Many non-standard businesses with a fake, nickel content of less than 1% or chromium content are also very low products such as 304-grade stainless steel, and some directly on the fastener header mark A2-70, causing market confusion. So everyone should pay attention to screening when choosing.

In summary, we can no longer use whether it is magnetic to judge whether it is authentic stainless steel.

XINCHI is a trustworthy fastener company, especially in furniture nuts. We have a factory,  founded in 2007. And we are the designated fastener supplier to“STAPLE”. As a trusted fastener supplier,  XINCHI can offer a wide range of high-quality fasteners, including nuts, screws, bolts, rivets, washers, etc. If you want to know more about fasteners or want to wholesale fasteners, please feel free to contact us. And then our experienced and expert service team will reply to you as soon as possible.