alics Blogs

People often have a able misunderstanding and will use magnets to check the quality and authenticity of seamless stainless steel tubes. If they are not, they will be non-magnetic and they are considered to be of high quality, otherwise they are fakes. In reality, this is the wrong view and it is one-sided. If this method is used to determine whether seamless stainless steel tubes are of high quality or not, then there will be “oopsies”.

In fact, there are many types of stainless steel and some products may not be used in daily life and production. Then, let’s look at what types of seamless stainless steel tubes can be classified into tissue structures at room temperature.

Stainless steel seamless steel pipe

1. Austenitic type: such as 304, 321, 316L, 310S, etc.; 2. Martensitic or ferritic type: such as 430, 420 series, 410, etc.; Austenitic type is non-magnetic or weakly magnetic, martensitic or ferritic is magnetic. Most stainless steel seamless tubes commonly used as decorative pipe sheets are austenitic 304 material, which is usually non-magnetic or weakly magnetic, but may also be magnetic due to fluctuations in chemical composition or different processing conditions caused by smelting, but this cannot be considered counterfeit or substandard.

As mentioned above, austenitic stainless steel seamless tubes are non-magnetic or weakly magnetic, while martensitic or ferritic are magnetic. A small amount of martensite or ferrite can be induced in austenitic 304 stainless steel due to composition bias or improper heat treatment during the smelting process. As a result, 304 stainless steel seamless steel pipe will have weak magnetic properties.

In addition, after cold working of 304 stainless steel seamless steel pipe, the organization will also be transformed into martensite. The greater the degree of cold working deformation, the more martensitic phase change, and the better the magnetic properties of the steel. Like a batch of steel strip, the Φ76 tube produced has no obvious magnetic induction strength, while the Φ9.5 tube produced has more obvious magnetic induction due to larger bending deformation. The deformation of the square rectangular tube is greater than that of the round tube, especially the corner deformation is more drastic and the magnetic induction is more pronounced. In order to completely eliminate the magnetism of 304 stainless steel seamless pipe due to the above reasons, the magnetism can be eliminated by high temperature solution treatment to restore and stabilize the austenite organization.