Stainless steel

In metallurgy, stainless steel (inox) is defined{{ref|AISI}} as a ferrous alloy with a minimum of 10.5% chromium content. The name originates from the fact that stainless steel stains, or rusts, less easily than ordinary steel. Stainless steel has higher resistance to oxidation (rust) and corrosion in several environments.

History

A few corrosion-resistant iron artifacts survive from antiquity. A famous (and very large) example is the Iron Pillar of Delhi, erected by order of Kumara Gupta I around the year AD 400. However, unlike stainless steel, these artifacts owe their durability not to chromium, but to their high phosphorus content, which promotes the formation of a solid protective layer of iron oxides, rather than the non-protective, cracked oxide layer that develops on most ironwork.

Related Topics:
Iron Pillar of Delhi - Kumara Gupta I - AD 400 - Phosphorus - Iron oxide

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The corrosion resistance of iron-chromium alloys was first recognized in 1821 by the French metallurgist Pierre Berthier, who noted their resistance against attack by some acids and suggested their use in cutlery. However, the metallurgists of the 19th century were unable to produce the combination of low carbon and high chromium found in most modern stainless steels, and the high-chromium alloys they could produce were too brittle to be of practical interest.

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1821 - French - Pierre Berthier - Cutlery

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This situation changed in the late 1890s, when Hans Goldschmidt of Germany developed an aluminothermic (thermite) process for producing carbon-free chromium. In the years 1904-1911, several researchers, particularly Leon Guillet of France, prepared alloys that would today be considered stainless steel. In 1911, Philip Monnartz of Germany reported on the relationship between the chromium content and corrosion resistance of these alloys.

Related Topics:
1890 - Hans Goldschmidt - Germany - Thermite - 1904 - 1911 - Leon Guillet - Philip Monnartz

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Harry Brearley of the Brown-Firth research laboratory in Sheffield, England is most commonly credited as the "inventor" of stainless steel. In 1913, while seeking an erosion-resistant alloy for gun barrels, he discovered and subsequently industrialized a martensitic stainless steel alloy. However, similar industrial developments were taking place contemporaneously at the Krupp Iron Works in Germany, where Eduard Maurer and Benno Strauss were developing an austenitic alloy (21% chromium, 7% nickel), and in the United States, where Christian Dantsizen and Frederick Becket were industrializing ferritic stainless.

Related Topics:
Harry Brearley - Sheffield, England - Krupp

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