If you ask someone, “is stainless steel magnetic?”, You may get all kinds of answers. Some people think that stainless steel is a completely nonmagnetic material. Others believe that stainless steel must be magnetic because it contains iron. However, like most things, the answer lies somewhere in between. In fact, some types of stainless steel are magnetic, while others are not.
In order to make stainless steel magnetic, the following requirements shall be met:
Stainless steel must contain iron
The crystal structure of stainless steel must be ferrite or martensite.
First of all, because stainless steel is a kind of steel, it means that their chemical composition must contain iron. This satisfies the first requirement. The second requirement is that the crystal structure of stainless steel must be ferrite or martensite. If stainless steel is mainly composed of austenite structure, it has no magnetism.
Depending on the type of stainless steel, magnetic and non-magnetic stainless steels can usually be combined. The following types of stainless steel are typical of magnetism:
Ferritic stainless steel, such as grades 409430 and 439
Martensitic stainless steel, such as grades 410, 420 and 440
Duplex stainless steel, e.g. grade 2205
Ferritic stainless steels are typically magnetic because their chemical composition contains a large amount of ferrite. Ferrite is a compound of iron and other elements. The combination of ferrite crystal structure and iron makes ferritic stainless steel magnetic. However, some ferritic stainless steels may have weaker magnetic pull than ordinary carbon steels.
Many martensitic stainless steels are magnetic. If iron is present, the unique crystal structure of martensitic steel can be ferromagnetic. As stainless steel is a kind of steel, its composition contains a lot of iron. This makes many martensitic stainless steels magnetic.
Duplex stainless steels are usually magnetic because they contain a mixture of austenite and ferrite. A large amount of ferrite (magnetic) makes duplex steel magnetic. However, since duplex stainless steels have more austenite than ferritic steels, their magnetic properties may be slightly lower.
Austenitic stainless steels contain a large amount of austenite, which makes them mostly non-magnetic. Although 304 and 316 stainless steels contain a large amount of iron in their chemical composition, austenite means that they are non ferromagnetic. However, if the crystal structure of austenitic stainless steel is changed by work hardening or special heat treatment, ferrite will be formed in some parts, making the steel partially magnetic.
Magnetic materials can have a great impact on the expected properties of materials, which depends on its application. If a material needs to be quickly classified from other materials, one material is magnetic, which makes the classification process very easy. Magnetic materials may cause problems during welding or other metal processing. The behavior of electric current in magnetic materials is also different.