Stainless steel covers a wide range of alloys with different properties. One property all stainless steels have in common is that they all contain at least 12 percent chromium. They can be divided into three main groups: Austenitic stainless steel, Ferritic stainless steel and Martensitic stainless steel.
Properties of Stainless Steel
Stainless steel is a type of alloy steel that resists rust and other forms of corrosion while having an attractive appearance.
As mentioned above, stainless steel contains chromium. This provides the unique stainless and corrosion resisting properties.
Stainless steel contains a unique self-healing property. Because of the alloying elements used, a thin, transparent layer is formed on the surface. If the surface is scratched or damaged otherwise, this thin layer, which is only a few atoms thick, immediately rebuilds with the assistance of oxygen from air or water. Therefore, stainless steel does not require any coating or other corrosion protection to remain bright and shiny even after decades of use.
Types of Stainless Steel
Austenitic Stainless Steels
This type of stainless steel is a part of the 200 series or 300 series. Austenitic stainless steels are non-magnetic and have high corrosion resistance. They can only be hardened by cold working—not by heat treatment. While they are highly formable, they are prone to stress corrosion cracking. The three sub-types include: straight, L and H. Popular straight types of grades include: 201, 202, 301, 302, 303, 304, 305, 308, 309, 310, 314, 316, 317, 321, 347, 348 and 384.
Compared to the straight types, L types have a higher corrosion resistance. Examples include 304L and 316L. Conversely, H types are suitable for use in high temperature environments. Austenitic stainless steels are utilized in shafts, valves, bolts, bushings, nuts, aircraft fittings, chemical equipment, food processing equipment, brewing equipment, cryogenic vessels and more.
Ferritic Stainless Steels
This type of stainless steel is a part of the 400 series. They are magnetic and have a lower ductility, as well as a lower corrosion resistance than the austenitic grades. However, they offer high resistance to stress corrosion cracking. Ferritic stainless steels are hardened by cold working and are not heat treatable. Some of the popular grades include 405, 409, 430, 434, 442, 436 and 446. Applications are typically heat exchangers, automotive fasteners, furnace parts and heater parts.
Martensitic Stainless Steels
This type of stainless steel is a part of the 400 series or 500 series. They are magnetic and have higher strength, higher wear resistance and higher fatigue resistance than the austenitic and ferritic grades. In addition, they can be heat treated as well. However, corrosion resistance is moderate and lower than the austenitic and ferritic grades. They are highly machinable. Some of the popular grades include 410, 414, 416, 420, 440 and 431. Major applications include machine parts, pump shafts, bolts, bushings, coal chutes, cutlery, hardware, jet engine parts, mining machinery, rifle barrels, screws, valves, aircraft fittings, fire extinguisher inserts and rivets.
These are just the properties of stainless steel. Stay tuned for the rest of metal properties series. Don’t hesitate to contact Bryan Hose & Gasket with the link below for more information on stainless steel properties.