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Stainless Steel Tubes will also be Magnetic?

Date:2019-05-07    keywords:stainless steel tubes, magentic

Usually people think that the magnet absorbs the stainless steel tube, verify its pros and cons and the authenticity. if it does not attract non-magnetic, then we think it is good material and genuine; On the contrary, the sucker has magnetic, it is considered a counterfeit fake. In fact, this is an extremely one-sided, unrealistic way of distinguishing mistakes. 

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

1. Austenitic type: such as 304, 321, 316, 310, etc.;
2. Martensite or ferrite: such as 430, 420, 410, etc.;
Austenite is non-magnetic or weakly magnetic, martensite or ferrite is magnetic.

Usually used as a decorative stainless steel tube is mostly austenite 304 material, generally it's non-magnetic or weak magnetic. Due to chemical composition fluctuations or processing conditions, it may also occur magnetic, but this can not be considered as a counterfeit or failed, What is the reason for this?

It is mentioned above that austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to segregation or improper heat treatment during smelting, a small amount of martensite or ferrite structure in austenite 304 stainless steel tube is caused. Thus, the 304 stainless steel tube will have weak magnetic properties.

In addition, the 304 stainless steel tube is cold-worked, and the structure is also converted to martensite. The greater the cold-process deformation, the more the martensite transformation, the greater the magnetism of the steel. Like a batch of steel strips, it produces Φ76 tubes with no obvious magnetic induction and produces Φ9.5 steel tubes. Due to the large deformation of the bending, the magnetic induction is obvious. The rectangular tube produced is larger than the round tube, especially the angled part, and the deformation is more intense and the magnetic is more obvious.

In order to completely eliminate the magnetic properties of the 304 steel pipe caused by the above reasons, the austenite structure can be restored by high-temperature solution treatment to eliminate the magnetic properties. In particular, the magnetic properties of the 304 stainless steel tube caused by the above reasons are not at the same level as the magnetic properties of other stainless steel tubes such as 430 and carbon steel. That is to say, the magnetic properties of the 304 steel tube always show weak magnetic properties. This tells us that if the stainless steel strip is weakly magnetic or not magnetic at all, it should be judged as 304 or 316 material; if it is the same as the magnetic steel, it shows strong magnetism, because it is judged not to be 304 material.

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