A common question when we talk about stainless steel is: is it magnetic? In this article, we will delve into the relationship between stainless steel and magnetism.
First, What is Stainless Steel?
Stainless steel is an alloy made of steel, chromium, nickel, and other elements. Its main feature is corrosion resistance, which makes it ideal for many different applications. There are many different types of stainless steel, including austenitic, ferritic, and martensitic.
Now let’s get back to the heart of the matter: Is Stainless Steel Magnetic?
The answer depends on the type of stainless steel. Ferritic and martensitic stainless steels are magnetic, while Austenitic stainless steels are not.
Why is there such a difference? This is related to the elements contained in stainless steel.
Austenitic stainless steel (such as 304, 316): This type of stainless steel is usually non-magnetic due to its high nickel content and stable austenite structure. Even after cold work, their magnetism is very weak.
Martensitic stainless steel (such as 410, 420): This stainless steel contains a high carbon content and its structure is mainly martensite, which makes it magnetic.
Ferritic stainless steel (such as 430): This type of stainless steel is mainly composed of a ferrite structure and has a certain degree of magnetism.
Therefore, whether stainless steel is magnetic depends on the specific type and alloy composition. If the stainless steel material you have is magnetic, it is likely to be martensitic or ferritic. If it is not magnetic, it may be austenitic.
So, how to determine the type of stainless steel? The easiest way is to use a magnetic test. We can quickly determine the kind of stainless steel using a magnetic tester. If the magnetic tester is adsorbed on the surface of the stainless steel, then the stainless steel is ferritic stainless steel or martensitic stainless steel. If the magnetic tester is not adsorbed on the surface, then the stainless steel is austenitic stainless steel.
It is important to note that the magnetic test can only be used to determine the type of stainless steel and does not determine the quality or corrosion resistance of the stainless steel. Therefore, when selecting stainless steel, it is still necessary to select the appropriate stainless steel material according to the specific application requirements.
Is 304 Stainless Steel Magnetic?
Recently, I heard reports that why the screws from 304 cold headings are magnetic? Is the material not 304 stainless steel? The magnetism of stainless steel is related to its internal physical structure (mainly the orientation of the electrons). Here, Huaxiao Stainless Steel Co., Ltd. will analyze the magnetism of stainless steel for everyone!
In real life, most people think that stainless steel is not magnetic, and use magnets to identify stainless steel. This method is very unscientific. First of all, zinc alloy and copper alloy can generally imitate the appearance and color of stainless steel, and there is no magnetism, and it is easy to be mistaken for stainless steel;
304 stainless steel is a common type of stainless steel and it is part of the austenitic family of stainless steels. Austenitic stainless steels, including 304 stainless steel, are typically non-magnetic. However, 304 stainless steel can become slightly magnetic during the cold working process.
During cold working, 304 stainless steel is subjected to deformation, such as bending, stretching, or twisting. This can cause the austenitic structure to be transformed into a martensitic structure, which is magnetic. However, the magnetic properties of cold-worked 304 stainless steel are typically weaker than those of ferritic or martensitic stainless steel.
It is important to note that the magnetic properties of 304 stainless steel can vary depending on the specific manufacturing process and conditions. In some cases, 304 stainless steel may exhibit some magnetic properties even in the annealed (non-cold-worked) state, but this is relatively rare.
Overall, while 304 stainless steel is generally considered non-magnetic, it can exhibit some magnetic properties under certain conditions. If magnetic properties are a critical factor for a specific application, it is important to consult with a materials expert to determine the best stainless steel alloy for the job.
Is 316 Stainless Steel Magnetic?
316 stainless steel, are non-magnetic. This is because they have a face-centered cubic (FCC) crystal structure that does not allow magnetic domains to form easily.
However, cold working or deformation of the material can introduce some magnetic properties, although the level of magnetism is usually very low. Additionally, if the 316 stainless steel is exposed to high temperatures (e.g., during welding), it can become magnetic due to the formation of a different crystal structure called ferrite.
Therefore, while 316 stainless steel is generally considered non-magnetic, its magnetic properties can be influenced by factors such as cold working, welding, and temperature.
Stainless steel is divided into 5 categories, namely austenite, martensite, ferrite, duplex steel, and precipitation hardening type.
200 series austenite-grades 202, 203, 204, 205, etc., these grades are non-magnetic, non-heat-treatable, have excellent forming and processing properties, and are widely used in washing machines, bathtubs, etc.
300 series austenite grades are 301, 302, 303, 304, 305, 308, 309, 310, 314, 316, 317, 321, 330, 347, etc., with obvious advantages in cold workability. These grades are non-magnetic, non-heat-treatable, and have excellent formability. The addition of the element molybdenum greatly improves corrosion resistance. These grades are widely used in food equipment, chemical equipment, etc.
400 series ferrite grades are 405, 409, 429, 430, 434, 436, 442, 446, etc. They are magnetic but cannot be heat-treated. These grades are mainly used in car interiors and kitchen appliances.
400 series martensite grades 403, 410, 414, 416, 420, 422, 431, 440, etc., are magnetic and heat-treatable and are mainly used in fasteners, pump shafts, and turbine blades.
Precipitation Hardening Stainless Steel There are 13-8, 15-5, 15-7, 17-4, and 17-7 grades, mainly used in valves, gears, petrochemical equipment, etc.
Duplex Stainless Steel grades are 329, 2205, 2304, 2507, 3RE60, etc. The stress corrosion cracking resistance of these grades is stronger than that of austenite, and the hardness is stronger than that of pure ferrite. Widely used in pipelines, pressure shafting, etc.
To sum up, the magnetism of stainless steel depends on its type. Austenitic stainless steels are magnetic, while ferritic and martensitic stainless steels are not. Using a magnetic tester can determine the type of stainless steel, but not it’s quality or corrosion resistance. When choosing stainless steel, it is necessary to choose the appropriate stainless steel material according to the specific application requirements.
So Where does the Stainless Steel Magnetic Come From?
According to the research of material physics, Stainless Steel Magnetic comes from the structure of electron spin, which belongs to quantum mechanical properties, which can be “upward” or “downward”. In ferromagnetic metals, electrons automatically rotate in the same direction, while in anti-ferromagnetic metal materials, some electrons follow a regular pattern, while neighboring electrons spin in the opposite direction or anti-parallel, but for triangular crystals For the electrons in the lattice, since the two electrons in each triangle must spin in the same direction, the spin structure no longer exists.
Generally speaking, austenitic stainless steel (represented by 304) is non-magnetic, but it may also have weak magnetic properties, while ferrite (mainly 430, 409L, 439, and 445NF, etc.) and martensite (with 410 Representative) are generally magnetic.
Some steel grades (such as 304, etc.) in stainless steel are classified as “non-magnetic stainless steel”, which means that their magnetic index is lower than a certain value, that is to say, generally, stainless steel is more or less magnetic.
In addition, as mentioned above, austenite is non-magnetic or weakly magnetic, while ferrite and martensite are magnetic. Due to composition segregation or improper heat treatment during smelting, a small amount of martensite will appear in austenitic 304 stainless steel. Body or ferrite structure, so weak magnetism will appear in 304 stainless steel. In addition, after 304 stainless steel is cold-worked, the structure will also be transformed into martensite. The greater the cold working deformation, the more martensite transformation and the stronger the magnetism.
If you want to eliminate the magnetism of 304 stainless steel, you can restore and stabilize the austenite structure through high-temperature solution treatment, thereby eliminating the magnetism.
Therefore, the magnetic properties of materials are determined by the regularity of the molecular arrangement and the isotropy of the electron spins. We think it is the physical properties of the material, and the corrosion resistance of the material is determined by the chemical composition of the material, which is the chemical composition of the material. Performance has nothing to do with whether the material is magnetic or not.
The above is the knowledge of whether stainless steel is magnetic or not summarized by Huaxiao Stainless Steel. I hope it can help you. More stainless steel knowledge will be updated continuously. I hope you will pay more attention!