The Most Comprehensive Introduction to Magnetic Stainless Steel

In daily life, most people may have some doubts such as: Are all stainless steels magnetic? Why is stainless steel not magnetic? And so on. Today, the editor Grand Metal will give you the most comprehensive introduction to magnetic stainless steel with these doubts.

Magnetic stainless steel refers to stainless steel that is magnetic under certain conditions. Its magnetism mainly depends on the crystal structure and chemical composition inside the stainless steel material. The crystal structure of stainless steel is what we call BBC (ferrite/martensite) and FCC (austenite) in daily life.

Stainless steel comes in the category of magnetic as well as non-magnetic.The type of steel can be identified by comparing different set points.The first condition or consideration is the stainless steel contains iron in its chemical structure, and the second requirement is the stainless steel must have a quartz structure designed in a martensitic or ferritic structure.If stainless steel is essentially composed of an austenite structure, then it will non-magnetic in nature.The Stainless Steel of the magnetic and non-magnetic type that can be classified based on the kind of stainless steel.Here are the magnetic types of stainless steel:

Ferritic stainless steels are commonly magnetic.This type of stainless steel contains a maximum amount of ferrite in its chemical structure.Ferrite is a composite of iron and additional elements.The combination of a ferritic crystal composition with iron produces ferritic stainless steel magnetic in nature.But, much ferritic stainless steel can have lower magnetic strength than conventional carbon steel.

Many of the martensitic stainless steel grades are magnetic.The unique crystal structure contains iron in its chemical composition, and it can be ferromagnetic.As stainless steel is one of the types of steel, this includes a sufficient amount of iron in its chemical composition.This makes martensitic stainless steel magnetic in nature.

Duplex stainless steels are most commonly magnetic in nature because they include a blend of ferrite and austenite.The abundant amount of ferrite is mixed in Duplex Steel which makes it magnetic.But, duplex stainless steels have a higher austenite blend than ferritic steels, which can be slightly weak magnetic.

Ferritic Stainless Steel

Ferritic is composed of iron and other elements. Since ferritic stainless steel typically contains large amounts of ferrite, they are usually magnetic. However, the strength of the magnetic pull varies among the different ferritic stainless steel types.

• 409 is an automotive exhaust grade.
• 430 and 430F are resistant to mildly corrosive environments.
• F20S is a ferritic alternative to grade 304 or 304L.
• F18MS / 444 is a ferritic alternative to grade 316 or 316L.

Martensitic Stainless Steel

Martensitic stainless steel contains chromium but no nickel. If iron is present, the crystal structure can be ferromagnetic. As a result, many of the different martensitic stainless steel types are magnetic.

• 410 is a standard grade suitable for low-duty hardened applications.
• 416 is a free-machining bar grade.
• 420 has a higher hardness level making it suitable for cutlery and cutting tools.
• 431 is primarily used for shafting due to its hardness and toughness.
• 440A, 440B, and 440C are very high hardness grades primarily used in the construction of cutting tools.

Duplex Stainless Steel

Duplex stainless steel is a blend of austenite and ferrite. Ferrite is the larger component of the two, so duplex stainless steel tends to be magnetic. Due to the presence of austenite, the magnetic strength of this type is typically lower than that of the previously discussed types of stainless steel.

• 2101 is an economical alternative to 304 and 316.
• 2304 is an alternative to 316.
• 2205 is highly resistant to pitting and stress corrosion.
• 2507 and 2507CU are also highly resistant to pitting and stress corrosion.

Austenitic Stainless Steel

Austenitic stainless steel contains a large quantity of chromium and nickel. The increased nickel content makes most austenitic stainless steel non-magnetic.

• 301, 301L, and 301LN are suitable for roll-formed structural components due to their high strength.
• 302HA is a low work hardening rate grade.
• 303 and 303Se are free-machining bar grades.
• 304, 304L and 304H are high corrosion and oxidation resistant
• 310, 310S and 310H are high temperature resistant.
• 316, 316L and 316H have increased resistance to pitting corrosion in chloride environments.
• 321, 321H and 347 are suitable for heavy section welding and higher temperature applications.
• 253MA is resistant to high temperature.
• 904L is highly resistant to general corrosion and pitting.

The first step in testing whether magnetic stainless steel is magnetic is a magnet test. This involves placing a magnet near the object. If the magnet is pulled toward it, it indicates that the stainless steel contains some magnetic components, probably ferrite or martensite. To check more clearly, X-ray diffraction can be used to analyze the presence of ferrite or martensite by examining the crystal structure of the stainless steel. In addition, a magnetic permeability meter can be used to more accurately measure the degree of magnetic properties of the material. The composition of the stainless steel should also be evaluated, as well as its heat treatment and processing history, as they have a significant impact on its magnetic properties.

Q: Are all stainless steel magnetic?

A: Not all types of stainless steel are magnetic. The magnetic properties of stainless steel depend on its chemical composition and the alloying elements it contains. Some stainless steel types, like ferritic and martensitic, are usually magnetic, while others, like austenitic steels, are typically non-magnetic.

Q: Why is 304 stainless steel non-magnetic?

A: 304 stainless steel is often non-magnetic because it is an austenitic steel, which means its crystal structure does not support strong magnetic properties. However, cold working or welding can introduce a weak magnetic pull in some cases.

Q: What type stainless steel should I choose for magnetic applications?

A: For magnetic applications, you should consider ferritic or martensitic stainless steels, which are known for their magnetic properties. These types of stainless steel contain iron and exhibit magnetic strength, making them suitable for applications requiring magnetic pull.

Q: Can magnet stick to stainless steel ?

A: A magnet can stick to stainless steel if the steel contains magnetic materials, like ferritic or martensitic stainless steel. However, austenitic grades, such as 304 or 316 stainless steel, are less likely to attract magnets unless they undergo specific processing that alters their magnetic properties.

Q: What causes magnetism in stainless steel?

A: Magnetism in stainless steel is primarily caused by the presence of iron and the arrangement of its crystal structure. Ferritic and martensitic stainless steels have a body-centered cubic structure that supports magnetism, while austenitic steels have a face-centered cubic structure that typically does not.

Q: Are 304 and 316 stainless steel magnetic?

A: Grades 304 and 316 stainless steel are both austenitic and typically non-magnetic in their annealed state. However, they can become slightly magnetic when subjected to cold working or deformation processes, which alter their crystalline structure.