If you saw our recent Tuesday Tip on the differences between stainless steel and aluminum foodservice equipment and supplies, then you’re already a little familiar with a few of the classifications of stainless steel. I wanted to take an opportunity to expand upon these classifications (five in all) and overview a few areas from series to gauges you are likely to come across when researching stainless steel equipment.
Stainless Steel Classifications
Austenitic stainless steel is a very common type as it’s one of the most weldable. It’s used for a plethora of industrial and consumer applications, and can be divided into three groups: chromium-nickel (300 series), manganese-chromium-nickel-nitrogen (200 series), and specialty alloys.
Another common type of stainless steel, ferritic steel is comprised of iron-chromium alloys. Qualities include good conductibility and formability. Some common types of ferritic steel include 409 and 405 series used in mufflers, kitchen counter and sinks, exhaust systems, etc.
Martensitic steels include series 403, 410 and 420. This steel is similar to ferritic steel, but contains more of a balance of Chromium and Nitrogen.
Duplex steel has a microstructure of equal amounts of ferritic and austenitic steel and usually contains around 25% chromium and 5% nickel. Duplex steel has a high yield strength and a greater resistance to corrosion cracking, and is primarily used in chemical plants and piping applications.
5. Precipitation Hardening
This type of stainless steel is characterized by it’s ability to be hardened by a solution and aging heat treatment. These are comprised of chromium and nickel.
Stainless Steel Gauges
The gauge is the thickness of the stainless steel. The lower the number of the gauge, the thicker and more durable the stainless steel. Common types of gauges are 18, 16, and 14. A 14 gauge worktable is much less susceptible to denting than an 18 gauge table.
The gauge of many types of stainless steel equipment and supplies, most notably stainless steel flatware, will include two numbers and may read something like 18/10, 18/8, or 18/0. This refers to the percentages of chromium and nickel, respectively, in the stainless steel alloy. Unlike how the lowest gauge is thicker than the higher gauges, the higher the nickel percentage has greater resistance to rust and corrosion.
Common Stainless Steel Series
The series of stainless steel relates to the the classification of stainless steel listed above. Some common types of series you are likely to come across include 200 series, 300 series, and 400 series.
200 series stainless steel contains 16-18% chromium, 3.5-5.5% nickel, 5.5-7.5% manganese, as well as smaller doses of sulfur, carbon, phosphorous, and nitrogen. 200 series usually refers to austenitic stainless steel, and is used in a variety of applications such as automotive parts, clamps, cookware, food service equipment, kitchen utensils, sinks, etc.
16-18% chromium, 6-8% nickel. 300 series is also an austenitic classification of stainless steel, offering good levels of conductibility and high strength with solid corrosion and oxidation resistance. It’s used in a variety of industrial products.
10.5-11.7% chromium and varying, but relatively low, degrees of nickel, carbon, manganese, silicon, sulfur, phosphorus and nitrogen. Contains titanium. Designed primarily for the automotive industry, in particular exhaust systems.
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You may also enjoy our blog on types of applications for stainless steel equipment.