Most people think that stainless steel is non-magnetic. Using magnets to judge the quality and authenticity of stainless steel pipes is very unscientific.
The answer is definitely negative.
There are many types of stainless steel, which can be divided into several categories according to organizational structure at room temperature:
- Austenitic types such as 304, 321, 316, 310, etc.;
- Martensite or ferrite type such as 430, 420, 410, etc.;
The austenite type is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic.
The most commonly used stainless steel pipe for decoration is 304 austenitic type, which is generally non-magnetic or weak-magnetic, but it may also appear magnetic due to smelting or processing, but this cannot be considered as unqualified.
Austenitic is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Due to segregation of components during smelting or improper heat treatment, it will cause a small amount of martensite or ferrite structure in austenitic 304 stainless steel. In this way, 304 stainless steel will have a weak magnetic. This is also why the duplex pipe is magnetic.
In addition, when 304 stainless steel is cold-treated, its structure will also be transformed into martensite. The greater the degree of cold working deformation, the more the martensite transformation, the greater the magnetic properties of the steel. To completely eliminate the magnetism caused by the above-mentioned reasons, the stable austenite structure can be restored by high-temperature solution treatment to eliminate the magnetism.
It is particularly emphasized here that the magnetic properties caused by the above reasons are completely different from those of other materials such as 430 and carbon steel, which means that the magnetic properties of 304 steel are weaker. If the magnetism of stainless steel is the same as that of carbon steel, showing strong magnetism, it may not be 304 or 316.