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Stainless steel : 276 is a group of iron-based alloys that contain a minimum of approximately 11% chromium,: 3 a composition that prevents the iron from rusting, as well as providing heat-resistant properties.: 3 Different types of stainless steel include the elements carbon (from 0.03% to greater than 1.00%), nitrogen, aluminium, silicon, sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum.: 3 Specific types of stainless steel are often designated by a three-digit number, e.g., 304 stainless . Stainless steel's resistance to ferric oxide formation results from the presence of chromium in the alloy, which forms a passive film that protects the underlying material from corrosion attack, and can self-heal in the presence of oxygen.: 3 Corrosion resistance can be increased further, by: The addition of nitrogen also improves resistance to pitting corrosion and increases mechanical strength. Thus, there are numerous grades of stainless steel with varying chromium an

The invention of stainless steel followed a series of scientific developments, starting in 1798 when chromium was first shown to the French Academy by Louis Vauquelin. In the early 1800s, James Stoddart, Michael Faraday, and Robert Mallet observed the resistance of chromium-iron alloys ("chromium steels") to oxidizing agents. Robert Bunsen discovered chromium's resistance to strong acids. The corrosion resistance of iron-chromium alloys may have been first recognized in 1821 by Pierre Berthier, who noted their resistance against attack by some acids and suggested their use in cutlery. In the 1840s, both Sheffield steelmakers and Krupp were producing chromium steel with the latter employing it for cannons in the 1850s. In 1861, Robert Forester Mushet took out a patent on chromium steel. These events led to the first production of chromium-containing steel by J. Baur of the Chrome Steel Works of Brooklyn for the construction of bridges. A U.S. Patent for the product was iss

This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( March 2020 ) (Learn how and when to remove this template message) There are five main families, which are primarily classified by their crystalline structure: austenitic, ferritic, martensitic, duplex, and precipitation hardening. Austenitic stainless steel edit Austenitic stainless steel is the largest family of stainless steels, making up about two-thirds of all stainless steel production (see production figures below). They possess an austenitic microstructure, which is a face-centered cubic crystal structure. This microstructure is achieved by alloying steel with sufficient nickel and/or manganese and nitrogen to maintain an austenitic microstructure at all temperatures, ranging from the cryogenic region to the melting point. Thus, austenitic stainless steels are not hardenable by heat treatment

This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( March 2020 ) (Learn how and when to remove this template message) Unlike carbon steel, stainless steels do not suffer uniform corrosion when exposed to wet environments. Unprotected carbon steel rusts readily when exposed to a combination of air and moisture. The resulting iron oxide surface layer is porous and fragile. In addition, as iron oxide occupies a larger volume than the original steel, this layer expands and tends to flake and fall away, exposing the underlying steel to further attack. In comparison, stainless steels contain sufficient chromium to undergo passivation, spontaneously forming a microscopically thin inert surface film of chromium oxide by reaction with the oxygen in the air and even the small amount of dissolved oxygen in the water. This passive film prevents further corrosion b

Physical properties edit Electricity and magnetism edit Like steel, stainless steels are relatively poor conductors of electricity, with significantly lower electrical conductivity than copper. In particular, the electrical contact resistance (ECR) of stainless steel arises as the result of the dense protective oxide layer, and limits its functionality in applications as electrical connectors . Copper alloys and nickel coated connectors tend to exhibit lower ECR values, and are preferred materials for such applications. Nevertheless stainless steel connectors are employed in situations with ECR poses a lower design criteria and corrosion resistance is required, for example in high temperatures and oxidizing environments . Magnetic properties edit Martensitic and ferritic stainless steels are magnetic. Ferritic steel consists of ferrite crystals, a form of iron with up to 0.025% carbon. Due to its cubic crystalline structure, ferritic steel only absorbs a small amount of carbon, which

This section does not cite any sources . Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. ( March 2020 ) (Learn how and when to remove this template message) Standard mill finishes can be applied to flat rolled stainless steel directly by the rollers and by mechanical abrasives. Steel is first rolled to size and thickness and then annealed to change the properties of the final material. Any oxidation that forms on the surface (mill scale) is removed by pickling, and a passivation layer is created on the surface. A final finish can then be applied to achieve the desired aesthetic appearance. The following designations are used to describe stainless steel finishes: No. 0: Hot-rolled, annealed, thicker plates No. 1: Hot-rolled, annealed and passivated No. 2D: Cold rolled, annealed, pickled and passivated No. 2B: Same as above with additional pass through highly polished rollers No. 2BA: Bright annealed (BA o