Stainless steelIn metallurgy, stainless steel (inox) is defined[1] as a ferrous alloy with a minimum of 10.5% chromium content. The name originates from the fact that stainless steel stains, corrodes or rusts less easily than ordinary steel. In the United States and world-wide, particularly in the aviation industry, this material is also called corrosion resistant steel when it is not detailed exactly to its alloy type and grade. PropertiesStainless steels have higher resistance to oxidation (rust) and corrosion in many natural and man made environments, however, it is important to select the correct type and grade of stainless steel for the particular application. High oxidation resistance in air at ambient temperature is normally achieved with additions of more than 12% (by weight) chromium. The chromium forms a passivation 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 water and air, protecting the metal beneath. Also, when the surface is scratched this layer quickly reforms. This phenomenon is called passivation by materials scientists, and is seen in other metals, such as aluminium. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together. When disassembled, the welded material may be torn and pitted, an effect that is known as galling. Commercial value of stainless steelThe pinnacle of New York's Chrysler Building is clad with stainless steel.Stainless steel's resistance to corrosion and staining, low maintenance, relative inexpense, and familiar luster make it an ideal base material for a host of commercial applications. There are over 150 grades of stainless steel, of which fifteen are most common. The alloy is milled into sheets, plates, bars, wire, and tubing to be used in cookware, cutlery, hardware, surgical instruments, major appliances, industrial equipment, and building material in skyscrapers and large buildings. The famous seven-story pinnacle of the Chrysler Building in New York City is adorned with gleaming stainless steel cladding. Stainless steel is 100% recyclable. In fact, over 50% of new stainless steel is made from remelted scrap metal, rendering it a somewhat eco-friendly material. CorrosionEven a high-quality alloy can corrode under certain conditions. Because these modes of corrosion are more exotic and their immediate results are less visible than rust, they often escape notice and cause problems among those who are not familiar with them. Pitting corrosionPassivation relies upon the tough layer of oxide described above. When deprived of oxygen (or when another species such as chloride competes as an ion), stainless steel lacks the ability to re-form a passivating film. In the worst case, almost all of the surface will be protected, but tiny local fluctuations will degrade the oxide film in a few critical points. Corrosion at these points will be greatly amplified, and can cause corrosion pits of several types, depending upon conditions. While the corrosion pits only nucleate under fairly extreme circumstances, they can continue to grow even when conditions return to normal, since the interior of a pit is naturally deprived of oxygen. In extreme cases, the sharp tips of extremely long and narrow pits can cause stress concentration to the point that otherwise tough alloys can shatter, or a thin film pierced by an invisibly small hole can hide a thumb sized pit from view. These problems are especially dangerous because they are difficult to detect before a part or structure fails. Pitting remains among the most common and damaging forms of corrosion in stainless alloys, but it can be prevented by ensuring that the material is exposed to oxygen (for example, by eliminating crevices) and protected from chloride wherever possible. Pitting corrosion can occur when stainless steel is subjected to high concentration of chloride ions (for example, sea water) and moderately high temperatures. Weld decay and knifeline attackDue to the elevated temperatures of welding or during improper heat treatment, chromium carbides can form in the grain boundaries of stainless steel. This chemical reaction robs the alloy of chromium in the zone near the grain boundary, making those areas much less resistant to corrosion. This creates a galvanic couple with the well-protected alloy nearby, which leads to weld decay (corrosion of the grain boundaries near welds) in highly corrosive environments. Special alloys, either with low carbon content or with added carbon "getters" such as titanium and niobium (in types 321 and 347, respectively), can prevent this effect, but the latter require special heat treatment after welding to prevent the similar phenomenon of knifeline attack. As its name implies, this is limited to a small zone, often only a few micrometres across, which causes it to proceed more rapidly. This zone is very near the weld, making it even less noticeable[2]. Modern steel making technologies largely avoid these problems by controlling the carbon content of stainless steels to <0.3% and historically such grades were referred to as "L" grades such as 316L; in practice most stainless steels are now produced at these low carbon contents. RougingStainless steel can actually rust quite rapidly if it fails to form its protective oxide layer. This tends to happen when the stainless has had carbon steel forced into its surface, as by being dragged over carbon steel during installation, brushing with carbon steel, grinding with a contaminated wheel, or temporary welds to carbon steel. See Corrosion Doctors on Rouging. Intergranular corrosionThis is a largely historical problem related to the high carbon contents of steels from the past, for modern steels it is vary rarely an issue. Some compositions of stainless steel are prone to intergranular corrosion when exposed to certain environments. When heated to around 700 °C, chromium carbide forms at the intergranular boundaries, depleting the grain edges of chromium, impairing their corrosion resistance. Steel in such condition is called sensitized. Steels with carbon content 0.06% undergo sensitization in about 2 minutes, while steels with carbon content under 0.02% are not sensitive to it. It is possible to reclaim sensitized steel by heating it to above 1000 °C and holding at this temperature for a given period of time dependent on the mass of the piece, followed by quenching it in water. This process dissolves the carbide particles, then keeps them in solution. It is also possible to stabilize the steel to avoid this effect and make it welding-friendly. Addition of titanium, niobium and/or tantalum serves this purpose; titanium carbide, niobium carbide and tantalum carbide form preferentially to chromium carbide, protecting the grains from chromium depletion. Use of extra-low carbon steels is another method and modern steel production usually ensures a carbon content of <0.03% at which level intergranular corrosion is not a problem. Light-gauge steel also does not tend to display this behavior, as the cooling after welding is too fast to cause effective carbide formation. Crevice corrosionIn the presence of reducing acids or exposition to reducing atmosphere, the passivation layer protecting steel from corrosion can break down. This wear can also depend on the mechanical construction of the parts, eg. under gaskets, in sharp corners, or in incomplete welds. Such crevices may promote corrosion, if their size allows penetration of the corroding agent but not its free movement. The mechanism of crevice corrosion is similar to pitting corrosion, though it happens at lower temperatures. Stress corrosion crackingStress corrosion cracking is a rapid and severe form of stainless steel corrosion. It forms when the material is subjected to tensile stress and some kinds of corrosive environments, especially chloride-rich environments (sea water) at higher temperatures. The stresses can result of the service loads, or can be caused by the type of assembly or residual stresses from fabrication (eg. cold working); the residual stresses can be relieved by annealing. This limits the usefulness of stainless steel for containing water with higher than few ppm content of chlorides at temperatures above 50 °C. Stress corrosion cracking applies only to austenitic stainless steels and depends on the nickel content. Sulphide stress crackingSulphide stress cracking is an important failure mode in the oil industry, where the steel comes into contact with liquids or gases with considerable hydrogen sulfide content, eg. sour gas. It is influenced by the tensile stress and is worsened in the presence of chloride ions. Very high levels of hydrogen sulfide apparently inhibit the corrosion. Rising temperature increases the influence of chloride ions, but decreases the effect of sulfide, due to its increased mobility through the lattice; the most critical temperature range for sulphide stress cracking is between 60-100 °C. Galvanic corrosionGalvanic corrosion occurs when a galvanic cell is formed between two dissimilar metals. The resulting electrochemical potential then leads to formation of an electric current that leads to electrolytic dissolving of the less noble material. This effect can be prevented by electrical insulation of the materials, eg. by using rubber or plastic sleeves or washers, keeping the parts dry so there is no electrolyte to form the cell, or keeping the size of the less-noble material significantly larger than the more noble ones (eg. stainless-steel bolts in an aluminum block won't cause corrosion, but aluminum rivets on stainless steel sheet would rapidly corrode. Contact corrosionContact corrosion is a combination of galvanic corrosion and crevice corrosion, occurring where small particles of suitable foreign material are embedded to the stainless steel. Carbon steel is a very common contaminant here, coming from nearby grinding of carbon steel or use of tools contaminated with carbon steel particles. The particle forms a galvanic cell, and quickly corrodes away, but may leave a pit in the stainless steel from which pitting corrosion may rapidly progress. Some workshops therefore have separate areas and separate sets of tools for handling carbon steel and stainless steel, and care has to be exercised to prevent direct contact between stainless steel parts and carbon steel storage racks. Particles of carbon steel can be removed from a contaminated part by passivation with dilute nitric acid, or by pickling with a mixture of hydrofluoric acid and nitric acid. See also Stainless steel - corrosion resistance Types of stainless steelThere are different types of stainless steels: when nickel, for instance is added the austenite structure of iron is stabilized. This crystal structure makes such steels non-magnetic and less brittle at low temperatures. For higher hardness and strength, carbon is added. When subjected to adequate heat treatment these steels are used as razor blades, cutlery, tools etc. Significant quantities of manganese have been used in many stainless steel compositions. Manganese preserves an austenitic structure in the steel as does nickel, but at a lower cost. Stainless steels are also classified by their crystalline structure:
The AISI defines the following grades among others:
Stainless steel finishesStandard 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 (scale) is removed by pickling, and the passivation layer is created on the surface. A final finish can then be applied to achieve the desired aesthetic appearance.
HistoryA 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 together with favorable local weather conditions promotes the formation of a solid protective passivation layer of iron oxides and phosphates, rather than the non-protective, cracked rust layer that develops on most ironwork. 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. 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. 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. Use in sculpture and building facadesAn art deco sculpture on the Niagara-Mohawk Power building in Syracuse, New YorkStainless steel was particularly in vogue during the art deco period. The most famous example of this is the upper portion of the Chrysler Building (illustrated above). Diners and fast food restaurants feature large ornamental panels, stainless fixtures and furniture. Owing to the durability of the material many of these buildings still retain their original and spectacular appearance. In recent years the forging of stainless steel has given rise to a fresh approach to architectural blacksmithing. The work of Giusseppe Lund illustrates this well. References
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The work of Giusseppe Lund illustrates this well. Also see: Suzuki Motorcycle/Scooter Naming Conventions. In recent years the forging of stainless steel has given rise to a fresh approach to architectural blacksmithing. Since then, Suzuki has established a reputation as a manufacturer of well-engineered sport motorcycles. Owing to the durability of the material many of these buildings still retain their original and spectacular appearance. However, it wasn't until 1976 when Suzuki introduced its first motorcycle with a four-stroke engine, the GS400 and GS750. Diners and fast food restaurants feature large ornamental panels, stainless fixtures and furniture. During the 1950's, 1960's and the better part of 1970's, the company manufactured motorcycles with two-stroke engines only, the biggest two-stroke model being the water-cooled triple-cylinder GT750. The most famous example of this is the upper portion of the Chrysler Building (illustrated above). Suzuki started manufacturing motorcycles in 1952, the first models being motorized bicycles. Stainless steel was particularly in vogue during the art deco period. The Geo and Chevrolet Tracker were Suzuki Vitaras by another name. 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. The Chevrolet Cruze and Holden Cruze are also on Suzuki platforms—again the Ignis's but with a Holden-designed body. In 1913, while seeking an erosion-resistant alloy for gun barrels, he discovered and subsequently industrialized a martensitic stainless steel alloy. Suzuki's Samurai/Sierra was also known as the Holden Drover between 1985 and 1987. Harry Brearley of the Brown-Firth research laboratory in Sheffield, England is most commonly credited as the "inventor" of stainless steel. Most of Mazda's (and Autozam's) smallest vehicles are made by Suzuki, as is the Nissan Moco. In 1911, Philip Monnartz of Germany reported on the relationship between the chromium content and corrosion resistance of these alloys. In Europe, the main rebadged Suzuki is the Subaru Justy and G3X Justy, which has been a version of its Swift and, more recently, its Ignis. In the years 1904–1911, several researchers, particularly Leon Guillet of France, prepared alloys that would today be considered stainless steel. Beginning with the Chevrolet Sprint, Suzuki has built cars for other manufacturers. This situation changed in the late 1890s, when Hans Goldschmidt of Germany developed an aluminothermic (thermite) process for producing carbon-free chromium. Suzuki also introduced a redesigned Grand Vitara as a 2006 model. 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. The Forenza gained wagon and hatchback body styles for 2005, with the hatchback sold under the Reno name. 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. In 2004, General Motors rebadged two Daewoo cars with the Suzuki name: the compact Forenza (Daewoo Nubira/Daewoo Lacetti) and the midsize Verona (Daewoo Magnus, formerly the Daewoo Leganza). However, unlike stainless steel, these artifacts owe their durability not to chromium, but to their high phosphorus content, which together with favorable local weather conditions promotes the formation of a solid protective passivation layer of iron oxides and phosphates, rather than the non-protective, cracked rust layer that develops on most ironwork. Suzuki was now down from two SUVs to one, and two cars to one. A famous (and very large) example is the Iron Pillar of Delhi, erected by order of Kumara Gupta I around the year AD 400. The Esteem also left, to be replaced with the Aerio for 2002. A few corrosion-resistant iron artifacts survive from antiquity. After 2001, the Swift (by then the most inexpensive car in America) had left the Suzuki lineup. A final finish can then be applied to achieve the desired aesthetic appearance. The Sidekick was replaced by the Vitara and the Grand Vitara for 1999. Any oxidation that forms on the surface (scale) is removed by pickling, and the passivation layer is created on the surface. In 1996, American Suzuki released the X-90 to replace the Samurai. Steel is first rolled to size and thickness and then annealed to change the properties of the final material. Worldwide Suzuki production reached more than 975,000 cars this year. Standard mill finishes can be applied to flat rolled stainless steel directly by the rollers and by mechanical abrasives. In 1995 American Suzuki introduced the Esteem and redesigned the Swift. The AISI defines the following grades among others:. The Swift and Sidekick were cousins to GM's Geo Metro and Geo Tracker and were mostly produced in Ingersoll, Canada by Suzuki and GM's joint venture, CAMI. Stainless steels are also classified by their crystalline structure:. In 1989, American Suzuki introduced the Swift and a new small SUV called the Sidekick. Manganese preserves an austenitic structure in the steel as does nickel, but at a lower cost. Both companies spent over a decade in court debating this issue with no winner. Significant quantities of manganese have been used in many stainless steel compositions. It was successful until Consumer Reports reportedly forced the Samurai to roll over in a 1988 test. When subjected to adequate heat treatment these steels are used as razor blades, cutlery, tools etc. No other Japanese company sold more cars in the United States in its first year than Suzuki. For higher hardness and strength, carbon is added. Also in 1985 (for the 1986 model year), the Samurai (a small off-roader; also known variously as the Jimny, Sierra and SJ410/SJ413 outside the US) was the first car introduced to the United States by the newly created American Suzuki Corp. This crystal structure makes such steels non-magnetic and less brittle at low temperatures. In 1985, Suzuki made an agreement with General Motors to meet the increasing demand for small cars and the Chevrolet Sprint (Suzuki Cultus in Japan) was introduced in the United States. There are different types of stainless steels: when nickel, for instance is added the austenite structure of iron is stabilized. During the 1970s, the models Suzuki Fronte (in different variations such as the 360 or the Viola) and Suzuki Jimny were produced. See also Stainless steel - corrosion resistance. In 1955 Suzuki introduced its first mass-produced car, the Suzulight. Particles of carbon steel can be removed from a contaminated part by passivation with dilute nitric acid, or by pickling with a mixture of hydrofluoric acid and nitric acid. In 1954 the company's name changed to Suzuki Motor Corporation. Some workshops therefore have separate areas and separate sets of tools for handling carbon steel and stainless steel, and care has to be exercised to prevent direct contact between stainless steel parts and carbon steel storage racks. This bike was popular, so in 1954 it introduced a second bicycle. The particle forms a galvanic cell, and quickly corrodes away, but may leave a pit in the stainless steel from which pitting corrosion may rapidly progress. In 1952 it created the motorized bicycle, called Power Free, which featured a 2x36cc engine. Carbon steel is a very common contaminant here, coming from nearby grinding of carbon steel or use of tools contaminated with carbon steel particles. It was founded in Hamamatsu, Shizuoka Prefecture Japan, by Michio Suzuki. Contact corrosion is a combination of galvanic corrosion and crevice corrosion, occurring where small particles of suitable foreign material are embedded to the stainless steel. The company started out as Suzuki Loom Works in 1909. stainless-steel bolts in an aluminum block won't cause corrosion, but aluminum rivets on stainless steel sheet would rapidly corrode. . by using rubber or plastic sleeves or washers, keeping the parts dry so there is no electrolyte to form the cell, or keeping the size of the less-noble material significantly larger than the more noble ones (eg. It has main production facilities located in 22 countries and areas around the world. This effect can be prevented by electrical insulation of the materials, eg. Suzuki Motor Corporation (スズキ株式会社) TYO: 7269 is a Japanese manufacturing company producing a range of small automobiles (especially Keicars), a full range of motorcycles, outboard motors, and a variety of other small combustion-powered engine products. The resulting electrochemical potential then leads to formation of an electric current that leads to electrolytic dissolving of the less noble material. List of Suzuki engines. Galvanic corrosion occurs when a galvanic cell is formed between two dissimilar metals. Suzuki Ozark 250. Rising temperature increases the influence of chloride ions, but decreases the effect of sulfide, due to its increased mobility through the lattice; the most critical temperature range for sulphide stress cracking is between 60-100 °C. Suzuki Eiger 400. Very high levels of hydrogen sulfide apparently inhibit the corrosion. Suzuki Vinson 500. It is influenced by the tensile stress and is worsened in the presence of chloride ions. Suzuki TwinPeaks 700. sour gas. Suzuki KingQuad 700. Sulphide stress cracking is an important failure mode in the oil industry, where the steel comes into contact with liquids or gases with considerable hydrogen sulfide content, eg. DR-Z Series - Four stroke. Stress corrosion cracking applies only to austenitic stainless steels and depends on the nickel content. RM-Z Series - Four stroke. This limits the usefulness of stainless steel for containing water with higher than few ppm content of chlorides at temperatures above 50 °C. RM Series - Two stroke. cold working); the residual stresses can be relieved by annealing. AN Burgman Series - Scooters. The stresses can result of the service loads, or can be caused by the type of assembly or residual stresses from fabrication (eg. Suzuki GV700/GV1200 Madura (85,86 only). It forms when the material is subjected to tensile stress and some kinds of corrosive environments, especially chloride-rich environments (sea water) at higher temperatures. Suzuki VS 600/750/1400 Intruder. Stress corrosion cracking is a rapid and severe form of stainless steel corrosion. Boulevard S50. The mechanism of crevice corrosion is similar to pitting corrosion, though it happens at lower temperatures. GSX-1300R Hayabusa. Such crevices may promote corrosion, if their size allows penetration of the corroding agent but not its free movement. DL 1000 V-Strom. under gaskets, in sharp corners, or in incomplete welds. GSX1100S-SZ, GSX750S-SF & GSX650 Katana. This wear can also depend on the mechanical construction of the parts, eg. FXR150. In the presence of reducing acids or exposition to reducing atmosphere, the passivation layer protecting steel from corrosion can break down. RG150/RGV150. Light-gauge steel also does not tend to display this behavior, as the cooling after welding is too fast to cause effective carbide formation. SV1000(S). Use of extra-low carbon steels is another method and modern steel production usually ensures a carbon content of <0.03% at which level intergranular corrosion is not a problem. SV650(S). Addition of titanium, niobium and/or tantalum serves this purpose; titanium carbide, niobium carbide and tantalum carbide form preferentially to chromium carbide, protecting the grains from chromium depletion. VX 800. It is also possible to stabilize the steel to avoid this effect and make it welding-friendly. VL 800 Volusia. This process dissolves the carbide particles, then keeps them in solution. VZ 800 Marauder. It is possible to reclaim sensitized steel by heating it to above 1000 °C and holding at this temperature for a given period of time dependent on the mass of the piece, followed by quenching it in water. DL 650 VStrom. Steels with carbon content 0.06% undergo sensitization in about 2 minutes, while steels with carbon content under 0.02% are not sensitive to it. Bandit (GSF) Series. Steel in such condition is called sensitized. GSX-R Series. When heated to around 700 °C, chromium carbide forms at the intergranular boundaries, depleting the grain edges of chromium, impairing their corrosion resistance. GSX Series. Some compositions of stainless steel are prone to intergranular corrosion when exposed to certain environments. GS Series. This is a largely historical problem related to the high carbon contents of steels from the past, for modern steels it is vary rarely an issue. Supercarry. See Corrosion Doctors on Rouging. Carry. This tends to happen when the stainless has had carbon steel forced into its surface, as by being dragged over carbon steel during installation, brushing with carbon steel, grinding with a contaminated wheel, or temporary welds to carbon steel. XL-7 - SUV. Stainless steel can actually rust quite rapidly if it fails to form its protective oxide layer. X-90 - SUV. Modern steel making technologies largely avoid these problems by controlling the carbon content of stainless steels to <0.3% and historically such grades were referred to as "L" grades such as 316L; in practice most stainless steels are now produced at these low carbon contents. Wagon R. This zone is very near the weld, making it even less noticeable[2]. Vitara/Sidekick- SUV. As its name implies, this is limited to a small zone, often only a few micrometres across, which causes it to proceed more rapidly. Verona - sedan from GM Daewoo. Special alloys, either with low carbon content or with added carbon "getters" such as titanium and niobium (in types 321 and 347, respectively), can prevent this effect, but the latter require special heat treatment after welding to prevent the similar phenomenon of knifeline attack. Suzuki Twin a hybrid keicar. This creates a galvanic couple with the well-protected alloy nearby, which leads to weld decay (corrosion of the grain boundaries near welds) in highly corrosive environments. SX4. This chemical reaction robs the alloy of chromium in the zone near the grain boundary, making those areas much less resistant to corrosion. Swift. Due to the elevated temperatures of welding or during improper heat treatment, chromium carbides can form in the grain boundaries of stainless steel. Samurai/Sierra. Pitting corrosion can occur when stainless steel is subjected to high concentration of chloride ions (for example, sea water) and moderately high temperatures. Reno - compact car from GM Daewoo. Pitting remains among the most common and damaging forms of corrosion in stainless alloys, but it can be prevented by ensuring that the material is exposed to oxygen (for example, by eliminating crevices) and protected from chloride wherever possible. Named after the nickname of Pakistan's province Sindh. These problems are especially dangerous because they are difficult to detect before a part or structure fails. Mehran - In Pakistan only. In extreme cases, the sharp tips of extremely long and narrow pits can cause stress concentration to the point that otherwise tough alloys can shatter, or a thin film pierced by an invisibly small hole can hide a thumb sized pit from view. Named after Margalla Hills of Islamabad. While the corrosion pits only nucleate under fairly extreme circumstances, they can continue to grow even when conditions return to normal, since the interior of a pit is naturally deprived of oxygen. Margalla - In Pakistan only. Corrosion at these points will be greatly amplified, and can cause corrosion pits of several types, depending upon conditions. Jimny - SUV. In the worst case, almost all of the surface will be protected, but tiny local fluctuations will degrade the oxide film in a few critical points. Ignis. When deprived of oxygen (or when another species such as chloride competes as an ion), stainless steel lacks the ability to re-form a passivating film. Grand Vitara - SUV. Passivation relies upon the tough layer of oxide described above. Fun - a restyling of the Opel Corsa. Because these modes of corrosion are more exotic and their immediate results are less visible than rust, they often escape notice and cause problems among those who are not familiar with them. Forenza - sedan from GM Daewoo. Even a high-quality alloy can corrode under certain conditions. Cervo/Whizzkid. In fact, over 50% of new stainless steel is made from remelted scrap metal, rendering it a somewhat eco-friendly material. Cappuccino also a Keicar. Stainless steel is 100% recyclable. Baleno. The famous seven-story pinnacle of the Chrysler Building in New York City is adorned with gleaming stainless steel cladding. Alto a Keicar. The alloy is milled into sheets, plates, bars, wire, and tubing to be used in cookware, cutlery, hardware, surgical instruments, major appliances, industrial equipment, and building material in skyscrapers and large buildings. Aerio/Liana - subcompact car. There are over 150 grades of stainless steel, of which fifteen are most common. Stainless steel's resistance to corrosion and staining, low maintenance, relative inexpense, and familiar luster make it an ideal base material for a host of commercial applications. When disassembled, the welded material may be torn and pitted, an effect that is known as galling. When stainless steel parts such as nuts and bolts are forced together, the oxide layer can be scraped off causing the parts to weld together. This phenomenon is called passivation by materials scientists, and is seen in other metals, such as aluminium. Also, when the surface is scratched this layer quickly reforms. It is, however, impervious to water and air, protecting the metal beneath. The layer is too thin to be visible, meaning the metal stays shiny. The chromium forms a passivation layer of chromium(III) oxide (Cr2O3) when exposed to oxygen. High oxidation resistance in air at ambient temperature is normally achieved with additions of more than 12% (by weight) chromium. Stainless steels have higher resistance to oxidation (rust) and corrosion in many natural and man made environments, however, it is important to select the correct type and grade of stainless steel for the particular application. . In the United States and world-wide, particularly in the aviation industry, this material is also called corrosion resistant steel when it is not detailed exactly to its alloy type and grade. The name originates from the fact that stainless steel stains, corrodes or rusts less easily than ordinary steel. In metallurgy, stainless steel (inox) is defined[1] as a ferrous alloy with a minimum of 10.5% chromium content. ISBN 0-13-359993-0. Jones, Principles and Prevention of Corrosion, 2nd edition, 1996, Prentice Hall, Upper Saddle River, NJ. ^ Denny A. ^ American Iron and Steel Institute (AISI). 8 - mirror finish. No. 7 - reflective finish. No. 6 - matt finish. No. 4 - fine abrasive finish. No. 3 - coarse abrasive finish applied mechanically. No. No, 2BA - Bright Anealed (BA) same as above with highly polished rollers. No, 2B - same as above with additional pass through polished rollers. No, 2D - cold rolled, annealed, pickled and passivated. 1 - Hot rolled, annealed and passivated. No. 0 - Hot Rolled Annealed, thicker plates. No. Type 630—most common PH stainless, better known as 17-4; 17% chromium, 4% nickel. 600 Series—martensitic precipitation hardening alloys
Type 430—decorative, e.g. Also known as "surgical steel". Type 420—"Cutlery Grade" martensitic; similar to the Brearley's original "rustless steel". Type 410—martensitic (high-strength iron/chromium). Type 409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only). Type 408—heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel. 400 Series—ferritic and martensitic alloys
Also known as "marine grade" stainless steel due to its increased ability to resist saltwater corrosion compared to type 304. Type 316—the next most common; for food and surgical stainless steel uses; Alloy addition of molybdenum prevents specific forms of corrosion. Type 304—the most common; the classic 18/8 stainless steel. Type 303—Free machining version of 304 via addition of sulfur. Also hardens rapidly during mechanical working. Type 301—highly ductile, for formed products. 300 Series—austenitic iron-chromium-nickel alloys
They are characterised by high chromium and lower nickel contents than austenitic stainless steels. Duplex steel have improved strength over austenitic stainless steels and also improved resistance to localised corrosion particularly pitting, crevice corrosion and stress corrosion cracking. Duplex stainless steels have a mixed microstructure of austenite and ferrite, the aim being to produce a 50:50 mix although in commercial alloys the mix may be 60:40. It is also known as "series-00" steel. It is quenched and magnetic. Martensitic stainless steel contains chromium (12-14%), molybdenum (0.2-1%), no nickel, and about 0.1-1% carbon (giving it more hardness but making the material a bit more brittle). 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. Common ferritic grades include 18Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo, and 29Cr-4Mo-2Ni. Most composition s include molybdenum; some, aluminium or titanium. They contain between 10.5% and 27% chromium and very little nickel, if any. Ferritic stainless steels are highly corrosion resistant, but far less durable than austenitic grades and cannot be hardened by heat treatment. The higher alloy content of "Superaustenitic" steels means they are fearsomely expensive and similar performance can usually be achieved using duplex steels at much lower cost. “Superaustenitic” stainless steels, such as alloy AL-6XN and 254SMO, exhibit great resistance to chloride pitting and crevice corrosion due to high Molybdenum contents (>6%) and nitrogen additions and the higher nickel content ensures better resistance to stress-corrosion cracking over the 300 series. Similarly 18/0 and 18/8 is also available. A typical composition is 18% chromium and 10% nickel, commonly known as 18/10 stainless is often used in flatware. 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. Austenitic stainless steels comprise over 70% of total stainless steel production. |