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Can magnets distinguish the quality of stainless steel pipes?
Can magnets distinguish the quality of stainless steel pipes?
We often use magnets to adsorb stainless steel pipes to verify their pros and cons and authenticity. If there is no magnetism, it is considered to be good, and the product is genuine at a fair price; if it is magnetism, it is considered to be a counterfeit. In fact, this is a one-sided and impractical method of identification.
Stainless steel pipes at room temperature can be divided into several categories according to their organizational structure:
1. Austenite type: such as 304, 321, 316, 310, etc.;
2. Martensite or ferrite type: such as 430, 420, 410, etc.;
Austenite is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. The stainless steel usually used as decorative tube sheet is mostly austenitic 304 material. Generally speaking, it is non-magnetic or weak magnetic. However, due to chemical composition fluctuations or different processing conditions caused by smelting, magnetism may also appear, but this cannot be considered as Counterfeit or substandard.
The reasons are as follows:
As mentioned above, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to component segregation or improper heat treatment during smelting, a small amount of martensite or ferrite structure will appear in the austenitic 304 stainless steel tube. In this way, the 304 stainless steel tube will have weak magnetism and will be attracted by the magnet.
In addition, the 304 stainless steel tube undergoes cold processing, the structure will also be transformed into martensite. The greater the degree of cold working deformation, the more martensite transformation, and the greater the magnetic properties of the 304 stainless steel tube. For example, the same batch of steel strips produces Φ76 tubes without obvious magnetic induction, and produces Φ19 tubes. Due to the large deformation of cold bending, the magnetic induction is more obvious. The deformation of the square rectangular tube is larger than that of the round tube, especially the corner part, the deformation is more intense, and the magnetism is more obvious.
This tells us that if stainless steel is weakly magnetic or not magnetic at all, it should be judged as 304 or 316 material; if it shows strong magnetism like carbon steel, it should be judged as not 304 material.
Therefore, relying on the traditional method of determining whether stainless steel is magnetic is likely to suffer.
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