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49-455: The Ruan Center is locally known as the "rusty skyscraper", for its Cor-Ten steel cladding that sheds rust. The exterior skin is composed of 1,600 US tons of Cor-Ten steel, and 4,700 tons of structural steel were used in the building's frame. The building consists mainly of office space and is connected to Des Moines' skywalk system. The 33rd and 34th floors are home to the Des Moines Club,

98-404: A coil, are caused by the coiling process. When these conditions are undesirable, it is essential for suppliers to be informed to provide appropriate materials. The presence of YPE is influenced by chemical composition and mill processing methods such as skin passing or temper rolling, which temporarily eliminate YPE and improve surface quality. However, YPE can return over time due to aging, which

147-461: A distinct upper yield point or a delay in work hardening. These tensile testing phenomena, wherein the strain increases but stress does not increase as expected, are two types of yield point elongation. Yield Point Elongation (YPE) significantly impacts the usability of steel. In the context of tensile testing and the engineering stress-strain curve, the Yield Point is the initial stress level, below

196-404: A mechanical component, since it represents the upper limit to forces that can be applied without producing permanent deformation. For most metals, such as aluminium and cold-worked steel , there is a gradual onset of non-linear behavior, and no precise yield point. In such a case, the offset yield point (or proof stress ) is taken as the stress at which 0.2% plastic deformation occurs. Yielding

245-577: A private members-only restaurant. The Ruan Center was named one of the 50 Most Significant Iowa Buildings of the 20th Century by the Iowa chapter of the American Institute of Architects . This article about a building or structure in Iowa is a stub . You can help Misplaced Pages by expanding it . This Des Moines, Iowa -related article is a stub . You can help Misplaced Pages by expanding it . Cor-Ten steel Weathering steel , often referred to by

294-412: A process known as bowing or ringing, in which a new ring of dislocations is created around the particle. The shearing formula goes as: and the bowing/ringing formula: In these formulas, r particle {\displaystyle r_{\text{particle}}\,} is the particle radius, γ particle-matrix {\displaystyle \gamma _{\text{particle-matrix}}\,}

343-464: A scale to measure strengths on another. Hardness testing can therefore be an economical substitute for tensile testing, as well as providing local variations in yield strength due to, e.g., welding or forming operations. For critical situations, tension testing is often done to eliminate ambiguity. However, it is possible to obtain stress-strain curves from indentation-based procedures, provided certain conditions are met. These procedures are grouped under

392-425: Is a gradual failure mode which is normally not catastrophic , unlike ultimate failure . For ductile materials, the yield strength is typically distinct from the ultimate tensile strength , which is the load-bearing capacity for a given material. The ratio of yield strength to ultimate tensile strength is an important parameter for applications such steel for pipelines , and has been found to be proportional to

441-914: Is available in Type 1 and Type 2. Both have different applications based on the thickness. Type 1 is often used in housing structures, construction industry and freight cars. The Type 2 steel, which is also called Corten B, is used primarily in urban furnishing, passenger ships or cranes. A588 has a yield strength of at least 50 ksi (340 MPa), and ultimate tensile strength of 70 ksi (480 MPa) for all rolled shapes and plate thicknesses up to 4 in (100 mm) thick. Plates from 4–5 in (102–127 mm) have yield strength at least 46 ksi (320 MPa) and ultimate tensile strength at least 67 ksi (460 MPa), and plates from 5–8 in (127–203 mm) thick have yield strength at least 42 ksi (290 MPa) and ultimate tensile strength at least 63 ksi (430 MPa). Weathering steel

490-425: Is no more corrosion-resistant than conventional steel, because the protective patina will not form in time to prevent corrosion over a localized area of attack such as a small paint failure. These cars were retired by 2016. Weathering steel was used to build the exterior of Barclays Center , made up of 12,000 pre-weathered steel panels engineered by ASI Limited & SHoP Construction. The New York Times says of

539-496: Is now best known was a welcome benefit discovered soon after, prompting USS to apply the trademarked name Cor-Ten. Because of its inherent toughness, this steel is still used extensively for bulk transport, intermodal shipping containers and bulk storage. Railroad passenger cars were also being built with Cor-Ten, albeit painted, by Pullman-Standard for the Southern Pacific from 1936, continuing through commuter coaches for

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588-468: Is often difficult to precisely define yielding due to the wide variety of stress–strain curves exhibited by real materials. In addition, there are several possible ways to define yielding: Yielded structures have a lower stiffness, leading to increased deflections and decreased buckling strength. The structure will be permanently deformed when the load is removed, and may have residual stresses. Engineering metals display strain hardening, which implies that

637-550: Is popularly used in outdoor sculptures for its distressed antique appearance. One example is the large Chicago Picasso sculpture, which stands in the plaza of the Daley Center Courthouse in Chicago, which is also constructed of weathering steel. Other examples include Barnett Newman 's Broken Obelisk ; several of Robert Indiana 's Numbers sculptures and his original Love sculpture; numerous works by Richard Serra ;

686-407: Is significantly lower than the expected theoretical value can be explained by the presence of dislocations and defects in the materials. Indeed, whiskers with perfect single crystal structure and defect-free surfaces have been shown to demonstrate yield stress approaching the theoretical value. For example, nanowhiskers of copper were shown to undergo brittle fracture at 1 GPa, a value much higher than

735-462: Is the magnitude of the Burgers vector , and ρ {\displaystyle \rho } is the dislocation density. By alloying the material, impurity atoms in low concentrations will occupy a lattice position directly below a dislocation, such as directly below an extra half plane defect. This relieves a tensile strain directly below the dislocation by filling that empty lattice space with

784-401: Is the strain induced in the lattice due to adding the impurity. Where the presence of a secondary phase will increase yield strength by blocking the motion of dislocations within the crystal. A line defect that, while moving through the matrix, will be forced against a small particle or precipitate of the material. Dislocations can move through this particle either by shearing the particle or by

833-420: Is the surface tension between the matrix and the particle, l interparticle {\displaystyle l_{\text{interparticle}}\,} is the distance between the particles. Where a buildup of dislocations at a grain boundary causes a repulsive force between dislocations. As grain size decreases, the surface area to volume ratio of the grain increases, allowing more buildup of dislocations at

882-853: The Alamo sculpture in Manhattan, NY; the Barclays Center , Brooklyn , New York ; the Angel of the North , Gateshead ; and Ribbons , a sculpture by Pippa Hale , celebrating women in Leeds; and Broadcasting Tower at Leeds Beckett University . It is also used in bridge and other large structural applications such as the New River Gorge Bridge , the second span of the Newburgh–Beacon Bridge (1980), and

931-611: The Israel Museum Art Garden in Jerusalem , Israel. In Denmark, all masts for supporting the catenary on electrified railways are made of weathering steel for aesthetic reasons. Weathering steel was used in 1971 for the Highliner electric cars built by the St. Louis Car Company for Illinois Central Railroad. The use of weathering steel was seen as a cost-cutting move in comparison with

980-489: The Kasper Salin Prize . Using weathering steel in construction presents several challenges. Ensuring that weld-points weather at the same rate as the other materials may require special welding techniques or material. Weathering steel is not rustproof in itself: if water is allowed to accumulate on the surface of the steel, it will experience a higher corrosion rate, so provision for drainage must be made. According to

1029-612: The NTSB , lack of drainage is what ultimately led to the Collapse of the Fern Hollow Bridge . Weathering steel is sensitive to humid subtropical climates, and in such environments it is possible that the protective patina may not stabilize but instead continue to corrode. For example, the former Omni Coliseum , built in 1972 in Atlanta , never stopped rusting, and eventually large holes appeared in

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1078-680: The Rock Island Line in 1949. In 1964, the Moorestown Interchange was built over New Jersey Turnpike at milepost 37.02. This overpass is believed to be the first highway structure application of weathering steel. Other states including Iowa, Ohio, and Michigan followed soon after. Those were followed by University of York Footbridge in the United Kingdom in 1967. Since then, the practice of using weathering steel in bridges has expanded to many countries. Weathering refers to

1127-664: The genericised trademark COR-TEN steel and sometimes written without the hyphen as corten steel , is a group of steel alloys which were developed to eliminate the need for painting by forming a stable external layer of rust . U.S. Steel (USS) holds the registered trademark on the name COR-TEN. The name COR-TEN refers to the two distinguishing properties of this type of steel : corrosion resistance and tensile strength . Although USS sold its discrete plate business to International Steel Group (now ArcelorMittal ) in 2003, it still sells COR-TEN branded material in strip mill plate and sheet forms. The original COR-TEN received

1176-433: The strain hardening exponent . In solid mechanics , the yield point can be specified in terms of the three-dimensional principal stresses ( σ 1 , σ 2 , σ 3 {\displaystyle \sigma _{1},\sigma _{2},\sigma _{3}} ) with a yield surface or a yield criterion . A variety of yield criteria have been developed for different materials. It

1225-420: The applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible and is known as plastic deformation . The yield strength or yield stress is a material property and is the stress corresponding to the yield point at which the material begins to deform plastically. The yield strength is often used to determine the maximum allowable load in

1274-419: The chemical composition of these steels, allowing them to exhibit increased resistance to atmospheric corrosion compared to other steels. This is because the steel forms a protective layer on its surface under the influence of the weather. The corrosion-retarding effect of the protective layer is produced by the particular distribution and concentration of alloying elements in it. It is not yet clear how exactly

1323-419: The contemporary railcar standard of stainless steel . A subsequent order in 1979 was built to similar specs, including weathering steel bodies, by Bombardier. The cars were painted, a standard practice for weathering steel railcars. The durability of weathering steel did not live up to expectations, with rust holes appearing in the railcars. Painting may have contributed to the problem, as painted weathering steel

1372-591: The creation of the Australian Centre for Contemporary Art (ACCA) and MONA . It is very widely used in marine transportation, in the construction of intermodal containers as well as visible sheet piling along recently widened sections of London's M25 motorway . The first use of weathering steel for architectural applications was the John Deere World Headquarters in Moline, Illinois . The building

1421-596: The elements; the research continued into the 1920s and c.  1926 it was discovered that phosphorus content also helps with the corrosion resistance. In 1933 the United States Steel Corporation decided to commercialize the results of their studies and patented a steel with exceptional mechanical resistance, primarily for use in railroad hopper cars , for the handling of heavy bulk loads including coal, metal ores , other mineral products and grain . The controlled corrosion for which this material

1470-462: The grain edge. Since it requires a lot of energy to move dislocations to another grain, these dislocations build up along the boundary, and increase the yield stress of the material. Also known as Hall-Petch strengthening, this type of strengthening is governed by the formula: where The theoretical yield strength of a perfect crystal is much higher than the observed stress at the initiation of plastic flow. That experimentally measured yield strength

1519-468: The impurity atom. The relationship of this mechanism goes as: where τ {\displaystyle \tau } is the shear stress , related to the yield stress, G {\displaystyle G} and b {\displaystyle b} are the same as in the above example, C s {\displaystyle C_{s}} is the concentration of solute and ϵ {\displaystyle \epsilon }

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1568-400: The lattice energy and move the atoms in the top plane over the lower atoms and into a new lattice site. The applied stress to overcome the resistance of a perfect lattice to shear is the theoretical yield strength, τ max . The stress displacement curve of a plane of atoms varies sinusoidally as stress peaks when an atom is forced over the atom below and then falls as the atom slides into

1617-646: The material is. The original A242 alloy has a yield strength of 50 kilopounds per square inch (340  MPa ) and ultimate tensile strength of 70 ksi (480 MPa) for light-medium rolled shapes and plates up to 0.75 inches (19 mm) thick. It has yield strength of 46 ksi (320 MPa) and ultimate strength of 67 ksi (460 MPa) for medium weight rolled shapes and plates from 0.75–1 inch (19–25 mm) thick. The thickest rolled sections and plates – from 1.5–4 in (38–102 mm) thick have yield strength of 42 ksi (290 MPa) and ultimate strength of 63 ksi (430 MPa). ASTM A242

1666-415: The material resulted in a discoloration, known as "bleeding" or "runoff", of the surrounding city sidewalks and nearby buildings. A cleanup effort was orchestrated by the corporation once weathering was complete to clean the markings. A few of the nearby sidewalks were left uncleaned, and remain a rust color. This problem has been reduced in newer formulations of weathering steel. Staining can be prevented if

1715-410: The material), a larger stress must be applied. This thus causes a higher yield stress in the material. While many material properties depend only on the composition of the bulk material, yield strength is extremely sensitive to the materials processing as well. These mechanisms for crystalline materials include Where deforming the material will introduce dislocations , which increases their density in

1764-410: The material. This increases the yield strength of the material since now more stress must be applied to move these dislocations through a crystal lattice. Dislocations can also interact with each other, becoming entangled. The governing formula for this mechanism is: where σ y {\displaystyle \sigma _{y}} is the yield stress, G is the shear elastic modulus, b

1813-461: The material: "While it can look suspiciously unfinished to the casual observer, it has many fans in the world of art and architecture." In 2015, a new building for the KTH Royal Institute of Technology School of Architecture was completed on its campus. The use of weathering steel helped the futuristic shapes of the facade fit in well with its much older surroundings and in 2015 it was awarded

1862-647: The maximum stress, at which an increase in strain occurs without an increase in stress. This characteristic is typical of certain materials, indicating the presence of YPE. The mechanism for YPE has been related to carbon diffusion, and more specifically to Cottrell atmospheres . YPE can lead to issues such as coil breaks, edge breaks, fluting, stretcher strain, and reel kinks or creases, which can affect both aesthetics and flatness. Coil and edge breaks may occur during either initial or subsequent customer processing, while fluting and stretcher strain arise during forming. Reel kinks, transverse ridges on successive inner wraps of

1911-743: The next lattice point. where b {\displaystyle b} is the interatomic separation distance. Since τ = G γ and dτ/dγ = G at small strains (i.e. Single atomic distance displacements), this equation becomes: For small displacement of γ=x/a, where a is the spacing of atoms on the slip plane, this can be rewritten as: Giving a value of τ max {\displaystyle \tau _{\max }} τ max equal to: The theoretical yield strength can be approximated as τ max = G / 30 {\displaystyle \tau _{\max }=G/30} . During monotonic tensile testing, some metals such as annealed steel exhibit

1960-466: The patina formation differs from usual rusting, but it's established that drying of the wetted surface is necessary and that copper is the most important alloying element. The layer protecting the surface develops and regenerates continuously when subjected to the influence of the weather. In other words, the steel is allowed to rust in order to form the protective coating. The mechanical properties of weathering steels depend on which alloy and how thick

2009-517: The predicted time. Rainwater runoff from the slowly rusting steel stained the numerous large windows and increased maintenance costs. Corrosion without the formation of a protective layer apparently led to the need for emergency structural reinforcement and galvanizing in 1974, less than two years after opening. The U.S. Steel Tower in Pittsburgh, Pennsylvania , was constructed by U.S. Steel in part to showcase COR-TEN steel. The initial weathering of

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2058-537: The presence of atmospheric pollutants which catalyze corrosion. While the process is generally successful in large urban centers, the weathering rate is much slower in more rural environments. Uris Hall , a social sciences building on Cornell University 's main campus in Ithaca , a small city in Upstate New York , did not achieve the predicted surface finish on its Bethlehem Steel Mayari-R weathering steel framing within

2107-572: The standard designation A242 (COR-TEN A) from the ASTM International standards group. Newer ASTM grades are A588 (COR-TEN B) and A606 for thin sheet. All of the alloys are in common production and use. The surface oxidation generally takes six months to develop, but surface treatments can accelerate this to as little as one hour. The history of weathering steels began in the US in 1910s, when steels alloyed with different amounts of copper were exposed to

2156-411: The strength of bulk copper and approaching the theoretical value. The theoretical yield strength can be estimated by considering the process of yield at the atomic level. In a perfect crystal, shearing results in the displacement of an entire plane of atoms by one interatomic separation distance, b, relative to the plane below. In order for the atoms to move, considerable force must be applied to overcome

2205-438: The structure can be designed so that water does not drain from the steel onto concrete where stains would be visible. Yield strength In materials science and engineering , the yield point is the point on a stress–strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and will return to its original shape when

2254-414: The structure. This was a major factor in the decision to demolish it just 25 years after construction. The same thing can happen in environments laden with sea salt. Hawaii's Aloha Stadium , built in 1975, is one example of this. Weathering steel's normal surface weathering can also lead to rust stains on nearby surfaces. The rate at which some weathering steels form the desired patina varies strongly with

2303-435: The term Indentation plastometry . There are several ways in which crystalline materials can be engineered to increase their yield strength. By altering dislocation density, impurity levels, grain size (in crystalline materials), the yield strength of the material can be fine-tuned. This occurs typically by introducing defects such as impurities dislocations in the material. To move this defect (plastically deforming or yielding

2352-530: The yield stress is increased after unloading from a yield state. Yield strength testing involves taking a small sample with a fixed cross-section area and then pulling it with a controlled, gradually increasing force until the sample changes shape or breaks. This is called a tensile test. Longitudinal and/or transverse strain is recorded using mechanical or optical extensometers. Indentation hardness correlates roughly linearly with tensile strength for most steels, but measurements on one material cannot be used as

2401-539: Was designed by architect Eero Saarinen , and completed in 1964. The main buildings of Odense University (built 1971–1976), designed by Knud Holscher and Jørgen Vesterholt, are clad in weathering steel, earning them the nickname Rustenborg (Danish for "rusty fortress"). In 1977, Robert Indiana created a Hebrew version of the Love sculpture made from weathering steel using the four-letter word ahava (אהבה, "love" in Hebrew) for

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