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High oxidation resistance in air at ambient temperature is normally achieved with additions of more than 12% (by weight) chromium. The chromium forms a layer of chromium (III) oxide (Cr₂O₃) when exposed to oxygen. The layer is too thin to be visible, meaning the metal stays shiny. It is, however, impervious to waterDrinking water This article focuses on water as we experience it every day. The water (molecule) article describes water from a scientific and technical perspective. Water is an abundant substance on Earth. It exists in many forms, such as sea, rain, and and air, protecting the metal beneath. Also, when the surface is scratched this layer quickly reforms. When stainless steel parts such as nutA nut is a type of hardware fastener with a threaded hole. Nuts are usually hexagonal to permit tightening with a wrench but may also be square, knurled, winged or otherwise shaped. Along with a bolt, nuts are designed to capture and fasten objects togeths and boltThis article refers to the threaded fastener. For other meanings, see Screw (disambiguation A screw is a shaft with a helical groove formed on its surface. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine uses are forced together, the oxide layer can be scraped off causing the parts to weldWelding is the joining together of materials (typically metals or thermo plastics), usually by a fusion process. Most commonly, workpieces are welded by melting both of them and adding more molten metal or plastic to form a pool that cools to form a stron together. This effect is known as galling .

There are different types of stainless steels: when nickelThis article is about the element nickel. See also nickel (U. coin) and nickel (Canadian coin). Nickel is a metallic chemical element in the periodic table that has the symbol Ni and atomic number 28. Notable characteristics Nickel is silvery white metal, for instance is added the austeniteAustenite is a solid solution of carbon and iron that exists in steel above the critical temperature of 1333°F (about 723°C). It is named after Sir W. Roberts-Austen. Its face-centred cubic (FCC) structure allows it to hold a high proportion of carbon. structure of iron is stabilized and these steels become non- magnetic. For higher hardness and strength, carbonAlternative meaning: Carbon (computing Carbon is a chemical element in the periodic table that has the symbol C and atomic number 6. An abundant nonmetallic, tetravalent element, carbon has several allotropic forms: diamonds (hardest known mineral). Bindi is added. When subjected to adequate heat treatment these steels are used as razor blades, cutlery, tools etc.

In recent decades, significant quantities of manganese have come to be used in many stainless steel recipes. Manganese imparts similar qualities to the steel as does nickel, but at a lower cost.

Stainless steels are also classified by their crystalline structure:

• Austenitic stainless steels comprise over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy. A typical composition is 18% chromium and 8% nickel, commonly known as 18/8 stainless.

• Ferritic stainless steels are highly corrosion resistant, but far less durable than austenitic grades and cannot be hardened by heat treatment. They contain between 10.5% and 27% chromium and very little nickel, if any. Most recipes include molybdenum; some, aluminium or titanium. Common ferritic grades include 18Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo, and 29Cr-4Mo-2Ni.

• Martensitic stainless steels are not as corrosion resistant as the other two classes, but are extremely strong and tough as well as highly machineable, and can be hardened by heat treatment. They contain 11.5 to 18% chromium and significant amounts of carbon. Some grades include additional alloying elements in small quantities.

The AISI defines the following grades:

• 200 Series—austenitic iron-chromium-nickel-manganese alloys
• 300 Series—austenitic iron-chromium-nickel alloys
  • Type 301—highly ductile, for formed products
  • Type 303—equivalent to ISO [2] A1.
  • Type 304—the most common; austenitic (contains nickel); equivalent to ISO A2.
  • Type 316—for food and medical uses; contains nickel and molybdenum; also called 18-8; equivalent to ISO A4.
• 400 Series—ferritic and martensitic alloys
  • Type 408—heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
  • Type 409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
  • Type 410—martensitic (high-strength iron/chromium); equivalent to ISO C1.
  • Type 420 —"Cutlery Grade" martensitic; similar to the Brearley's original "rustless steel".
  • Type 430—decorative, e.g. for automotive trim; ferritic.