Stainless steel is fundamentally an alloy, a blend of metals, with the primary components being iron, chromium, and often nickel. The magnetic properties of stainless steel are largely determined by this alloy composition, with specific types demonstrating stronger magnetic behavior.
In the intricate world of stainless steel, understanding the magnetic properties of different types is crucial for anyone dealing with magnets. While the magnetism of stainless steel can seem like a complex topic, knowing the basics can significantly enhance its utility across a broad range of applications. Remember, when in doubt, a neodymium magnet can often provide the answer!
Below we'll review the most common types of stainless steel and their magnetic properties.
Austenitic Stainless Steel (Home Appliances)
When it comes to your home appliances, especially stainless steel refrigerators, you may have noticed an interesting phenomenon: some of them don't hold magnets. But why is this the case, when we've established that certain types of stainless steel are indeed magnetic? The answer lies in the specific type of stainless steel used in these refrigerators.
Most home appliances, including refrigerators, often use Austenitic stainless steel—specifically types 304 or 316. These variants are popular due to their high corrosion resistance, aesthetic appeal, and formability—qualities crucial for household appliances. However, the Austenitic family of stainless steel, characterized by high chromium and nickel content, is generally non-magnetic.
Ferritic Stainless Steel (Most Magnetic)
When dealing with magnets, particularly neodymium magnets, Ferritic stainless steel stands out for its remarkable magnetic properties. This is largely due to its high iron and chromium content and minimal nickel.
Among the Ferritic stainless steels, type 409, with 11% chromium content, is known for good corrosion resistance and formability, coupled with its magnetic nature. Type 430, another popular variant, contains 17% chromium, making it even more corrosion-resistant while still maintaining its magnetism. Finally, type 446, with a higher chromium content of as much as 27%, exhibits excellent resistance to high-temperature corrosion and is still attractive to magnets.
Martensitic Stainless Steel (Hardened)
In the Martensitic family, the 400 series, including type 410 and 420, show impressive magnetic characteristics. Type 410, a general-purpose stainless steel with 11.5% chromium, provides reasonable corrosion resistance and magnetism. On the other hand, type 420, with a higher carbon content, is a hardenable stainless steel offering excellent wear resistance and is also magnetic.
Notably, the magnetism of these Martensitic stainless steels, specifically 410 and 420, can enhance with heat treatment. Hence, if hardness and magnetism are both required in your application, Martensitic stainless steel should be your top choice.
Duplex Stainless Steel (Hybrid)
Duplex stainless steel, a hybrid that combines characteristics of Austenitic and Ferritic stainless steels, also displays magnetism. Known for their high strength and excellent resistance to stress corrosion cracking, Duplex steels like type 2205 also work well with neodymium magnets due to their mixed Austenitic-Ferritic structure.