Category: Stainless Steel

Stainless Steel

Stainless Steel – Wikipedia

Sttoko stainless steel di medan ainless steel is used for industrial equipment when it is important that the equipment lasts and can be kept clean

Stainless steel[1][dua][3]: 276  is any stainless steel medan of a group of ferrous alloys that contain a minimum of approximately 11% chromium,[4]: 3 [lima] a composition that largely inhibits the iron from rusting and provides heat-resistant properties.[4]: tiga [lima][6][7][8] Different types of stainless steel include the elements carbon, nitrogen, aluminium, silicon, sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum.[4]: 3  Specific types of stainless steel are often designated by their AISI three-digit number, e.g., 304 stainless.[9] The ISO 15510 standard lists the chemical compositions of stainless steels of the specifications in existing ISO, ASTM, EN, JIS, and GB standards in a useful interchange table.[10]

Stainless steel’s resistance to rusting 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.[4]: tiga  Corrosion resistance can be increased further by the following means:increase chromium content to more than 11%[5]add nickel to at least 8%[lima]add molybdenum (which also improves resistance to pitting corrosion)[5]

The addition of nitrogen also improves resistance to pitting corrosion and increases mechanical strength.[lima] Thus, there are numerous grades of stainless steel with varying chromium and molybdenum contents to suit the environment the alloy must endure.[11]

Resistance to corrosion and staining, low maintenance, and familiar luster make stainless steel an ideal material for many applications where both the strength of steel and corrosion resistance are required. Moreover, stainless steel can be rolled into sheets, plates, bars, wire, and tubing. These can be used in cookware, cutlery, surgical instruments, major appliances, vehicles, construction material in large buildings, industrial equipment (e.g., in paper mills, chemical plants, water treatment), and storage tanks and tankers for chemicals and food products.

The biological cleanability of stainless steel is superior to both aluminum and copper, having a biological cleanability comparable to glass.[12] Its cleanability, strength, and corrosion resistance have prompted the use of stainless steel in pharmaceutical and food processing plants.[13]Properties[edit]

This section needs expansion with: information on physical properties other than magnetic and electric contact resistance. Missing is density, hardness, thermal conduction, etc.. You can help by adding to it.(August 2021)

Like steel, stainless steels are a relatively poor conductor of electricity, with significantly lower electrical conductivity than copper. In particular, the electrical contact resistance (ECR) of stainless steel arises as to the result of the dense protective oxide layer and limits its functionality in applications as electrical connectors.[14] 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 where ECR poses a lower design criteria and corrosion resistance is required, for example in high temperatures and oxidizing environments.[15]

As with all other alloys, the melting point of stainless steel is expressed in the form of a range of temperatures, and not a singular temperature.[16] This temperature range goes from 1,400 to 1,530 °C (dua,550 to dua,790 °F)[17] depending on the specific consistency of the alloy in question.

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 consists of one iron in each corner and a central iron atom. The central atom is responsible for its magnetic properties. Grades with low coercive field have been developed for electro-valves used in household appliances and for injection systems in internal combustion engines. Some applications require non-magnetic materials, such as magnetic resonance imaging. Annealed austenitic stainless steels are usually non-magnetic, though work hardening can make cold-formed austenitic stainless steels slightly magnetic. Sometimes, if austenitic steel is bent or cut, magnetism occurs along the edge of the stainless steel because the crystal structure rearranges itself.[citation needed]Magnetic permeability of some austenitic stainless steel grades after annealing dua hours at 1050 °C[18]EN gradeMagnetic permeability, μ1.43071.0561.43011.0111.44041.1001.44351.000

Galling, sometimes called cold welding, is a form of severe adhesive wear, which can occur when two metal surfaces are in relative motion to each other and under heavy pressure. Austenitic stainless steel fasteners are particularly susceptible to thread galling, though other alloys that self-generate a protective oxide surface film, such as aluminium and titanium, are also susceptible. Under high contact-force sliding, this oxide can be deformed, broken, and removed from parts of the component, exposing the bare reactive metal. When the two surfaces are of the same material, these exposed surfaces can easily fuse. Separation of the two surfaces can result in surface tearing and even complete seizure of metal components or fasteners.[19][20] Galling can be mitigated by the use of dissimilar materials (bronze against stainless steel) or using different stainless steels (martensitic against austenitic). Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling. Nitronic 60, made by selective alloying with manganese, silicon, and nitrogen, has demonstrated a reduced tendency to gall.[20]History[edit]

An announcement, as it appeared in the 1915 New York Times, of the development of stainless steel in Sheffield, England.[21]

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, British scientists 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.[22]

In the 1840s, both of Britain’s Sheffield steelmakers and then Krupp of Germany were producing chromium steel with the latter employing it for cannons in the 1850s.[23] In 1861, Robert Forester Mushet took out a patent on chromium steel in Britain.[24]

These events led to the first American 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 issued in 1869.[1]: 2261 [25] This was followed with recognition of the corrosion resistance of chromium alloys by Englishmen John T. Woods and John Clark, who noted ranges of chromium from 5–30%, with added tungsten and “medium carbon”. They pursued the commercial value of the innovation via a British patent for “Weather-Resistant Alloys”.[1]: 261, 11 [26][full citation needed]

In the late 1890s, German chemist Hans Goldschmidt developed an aluminothermic (thermite) process for producing carbon-free chromium.[27] Between 1904 and 1911, several researchers, particularly Leon Guillet of France, prepared alloys that would be considered stainless steel today.[27][28]

In 1908, the Essen firm Friedrich Krupp Germaniawerft built the 366-ton sailing yacht Germania featuring a chrome-nickel steel hull in Germany. In 1911, Philip Monnartz reported on the relationship between chromium content and corrosion resistance.[29] On 17 October 1912, Krupp engineers Benno Strauss and Eduard Maurer patentedas Nirosta the austenitic stainless steel[30][31][32][29] known today as 18/8 or AISI Type 304.[33]

Similar developments were taking place in the United States, where Christian Dantsizen of General Electric[33] and Frederick Becket (1875-1942) at Union Carbide were industrializing ferritic stainless steel.[34] In 1912, Elwood Haynes applied for a US patent on a martensitic stainless steel alloy, which was not granted until 1919.[35]Harry Brearley[edit]