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62-594: The Galton Bridge is a cast-iron bridge in Smethwick , near Birmingham , in the West Midlands of England. Opened in 1829 as a road bridge, the structure has been pedestrianised since the 1970s. It was built by Thomas Telford to carry a road across the new main line of the Birmingham Canal, which was built in a deep cutting. The bridge is 70 feet (21 metres) above the canal, making it reputedly

124-751: A cupola , but in modern applications, it is more often melted in electric induction furnaces or electric arc furnaces. After melting is complete, the molten cast iron is poured into a holding furnace or ladle. Cast iron's properties are changed by adding various alloying elements, or alloyants . Next to carbon , silicon is the most important alloyant because it forces carbon out of solution. A low percentage of silicon allows carbon to remain in solution, forming iron carbide and producing white cast iron. A high percentage of silicon forces carbon out of solution, forming graphite and producing grey cast iron. Other alloying agents, manganese , chromium , molybdenum , titanium , and vanadium counteract silicon, and promote

186-464: A 10-tonne impeller) to be sand cast, as the chromium reduces cooling rate required to produce carbides through the greater thicknesses of material. Chromium also produces carbides with impressive abrasion resistance. These high-chromium alloys attribute their superior hardness to the presence of chromium carbides. The main form of these carbides are the eutectic or primary M 7 C 3 carbides, where "M" represents iron or chromium and can vary depending on

248-538: A colour scheme intended to enhance its features. It is maintained by the Canal and River Trust and lends its name to the nearby Smethwick Galton Bridge railway station . It is a grade   I listed building . The original Birmingham Canal was built from the late 1760s along a meandering route, connecting Birmingham to Wolverhampton via the Black Country coalfields in the modern-day West Midlands . One of

310-435: A decorative parapet and lamp-posts, also in cast iron. When built, it was believed to be the longest bridge over a canal and the highest single-span arch bridge in the world; Telford wrote in his memoirs "At the place of greatest excavation is erected the largest canal bridge in the world; it is made of iron." All the ironwork was cast by Horseley Ironworks at its canal-side factory in nearby Tipton . The name "Galton Bridge"

372-563: A rule of mixtures. In any case, they offer hardness at the expense of toughness . Since carbide makes up a large fraction of the material, white cast iron could reasonably be classified as a cermet . White iron is too brittle for use in many structural components, but with good hardness and abrasion resistance and relatively low cost, it finds use in such applications as the wear surfaces ( impeller and volute ) of slurry pumps , shell liners and lifter bars in ball mills and autogenous grinding mills , balls and rings in coal pulverisers . It

434-758: A series of six cast-iron arch bridges built by Telford to a similar design. The first was at Bonar Bridge in the Scottish Highlands, built in 1810, which became the prototype. Others include the Mythe Bridge at Tewkesbury , built three years before the Galton Bridge, and the Holt Fleet Bridge in Worcestershire, completed in 1828. The Galton Bridge is the only one of the six surviving without later modification; Bonar Bridge

496-424: A spongy steel without the stress concentration effects that flakes of graphite would produce. The carbon percentage present is 3-4% and percentage of silicon is 1.8-2.8%.Tiny amounts of 0.02 to 0.1% magnesium , and only 0.02 to 0.04% cerium added to these alloys slow the growth of graphite precipitates by bonding to the edges of the graphite planes. Along with careful control of other elements and timing, this allows

558-417: A wide range of applications and are used in pipes , machines and automotive industry parts, such as cylinder heads , cylinder blocks and gearbox cases. Some alloys are resistant to damage by oxidation . In general, cast iron is notoriously difficult to weld . The earliest cast-iron artefacts date to the 5th century BC, and were discovered by archaeologists in what is now Jiangsu , China. Cast iron

620-399: A year after it was opened. The Dee bridge disaster was caused by excessive loading at the centre of the beam by a passing train, and many similar bridges had to be demolished and rebuilt, often in wrought iron . The bridge had been badly designed, being trussed with wrought iron straps, which were wrongly thought to reinforce the structure. The centres of the beams were put into bending, with

682-438: Is added in the ladle or in the furnace, on the order of 0.5–2.5%, to decrease chill, refine graphite, and increase fluidity. Molybdenum is added on the order of 0.3–1% to increase chill and refine the graphite and pearlite structure; it is often added in conjunction with nickel, copper, and chromium to form high strength irons. Titanium is added as a degasser and deoxidizer, but it also increases fluidity. Vanadium at 0.15–0.5%

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744-439: Is added to cast iron to stabilize cementite, increase hardness, and increase resistance to wear and heat. Zirconium at 0.1–0.3% helps to form graphite, deoxidize, and increase fluidity. In malleable iron melts, bismuth is added at 0.002–0.01% to increase how much silicon can be added. In white iron, boron is added to aid in the production of malleable iron; it also reduces the coarsening effect of bismuth. Grey cast iron

806-455: Is cast into the centre of the structure, below the parapet, on both sides and "Horseley Iron Works 1829" is cast below both spandrels on both sides. In his memoirs, published posthumously, Telford described the Galton Bridge as an "extraordinary span". He explained that his decision to build such a high bridge and to build it in cast iron, then still a novel material, was one of "safety, combined with economy". A masonry bridge tall enough to reach

868-420: Is characterised by its graphitic microstructure, which causes fractures of the material to have a grey appearance. It is the most commonly used cast iron and the most widely used cast material based on weight. Most cast irons have a chemical composition of 2.5–4.0% carbon, 1–3% silicon, and the remainder iron. Grey cast iron has less tensile strength and shock resistance than steel, but its compressive strength

930-485: Is comparable to low- and medium-carbon steel. These mechanical properties are controlled by the size and shape of the graphite flakes present in the microstructure and can be characterised according to the guidelines given by the ASTM . White cast iron displays white fractured surfaces due to the presence of an iron carbide precipitate called cementite. With a lower silicon content (graphitizing agent) and faster cooling rate,

992-453: Is difficult to cool thick castings fast enough to solidify the melt as white cast iron all the way through. However, rapid cooling can be used to solidify a shell of white cast iron, after which the remainder cools more slowly to form a core of grey cast iron. The resulting casting, called a chilled casting , has the benefits of a hard surface with a somewhat tougher interior. High-chromium white iron alloys allow massive castings (for example,

1054-575: Is hemmed in between the Smethwick Station Bridge, a railway bridge built in the 1860s, on the west (Wolverhampton) side, and a partial infill of the cutting where a 1970s road scheme crosses the canal on the east (Birmingham) side. Construction work on the cutting began in 1827. It and the bridge opened in December 1829. Isambard Kingdom Brunel , then a young engineer, visited it the following year and described it as "prodigious". In

1116-605: Is known as the Iron Bridge in Shropshire , England. Cast iron was also used in the construction of buildings . Cast iron is made from pig iron , which is the product of melting iron ore in a blast furnace . Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of

1178-433: Is one of the most common alloying elements, because it refines the pearlite and graphite structures, improves toughness, and evens out hardness differences between section thicknesses. Chromium is added in small amounts to reduce free graphite, produce chill, and because it is a powerful carbide stabilizer; nickel is often added in conjunction. A small amount of tin can be added as a substitute for 0.5% chromium. Copper

1240-755: Is very hard, but brittle, as it allows cracks to pass straight through; grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing. Carbon (C), ranging from 1.8 to 4 wt%, and silicon (Si), 1–3 wt%, are the main alloying elements of cast iron. Iron alloys with lower carbon content are known as steel . Cast iron tends to be brittle , except for malleable cast irons . With its relatively low melting point, good fluidity, castability , excellent machinability , resistance to deformation and wear resistance , cast irons have become an engineering material with

1302-698: The Chirk Aqueduct and the Pontcysyllte Aqueduct , both of which remain in use following the recent restorations. The best way of using cast iron for bridge construction was by using arches , so that all the material is in compression. Cast iron, again like masonry, is very strong in compression. Wrought iron, like most other kinds of iron and indeed like most metals in general, is strong in tension, and also tough – resistant to fracturing. The relationship between wrought iron and cast iron, for structural purposes, may be thought of as analogous to

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1364-527: The Congo region of the Central African forest, blacksmiths invented sophisticated furnaces capable of high temperatures over 1000 years ago. There are countless examples of welding, soldering, and cast iron created in crucibles and poured into molds. These techniques were employed for the use of composite tools and weapons with cast iron or steel blades and soft, flexible wrought iron interiors. Iron wire

1426-542: The Warring States period . This is based on an analysis of the artifact's microstructures. Because cast iron is comparatively brittle, it is not suitable for purposes where a sharp edge or flexibility is required. It is strong under compression, but not under tension. Cast iron was invented in China in the 5th century BC and poured into molds to make ploughshares and pots as well as weapons and pagodas. Although steel

1488-403: The surface tension to form the graphite into spheroidal particles rather than flakes. Due to their lower aspect ratio , the spheroids are relatively short and far from one another, and have a lower cross section vis-a-vis a propagating crack or phonon . They also have blunt boundaries, as opposed to flakes, which alleviates the stress concentration problems found in grey cast iron. In general,

1550-707: The 13th century and other travellers subsequently noted an iron industry in the Alburz Mountains to the south of the Caspian Sea . This is close to the silk route , thus the use of cast-iron technology being derived from China is conceivable. Upon its introduction to the West in the 15th century it was used for cannon and shot . Henry VIII (reigned 1509–1547) initiated the casting of cannon in England. Soon, English iron workers using blast furnaces developed

1612-533: The 1720s and 1730s by a small number of other coke -fired blast furnaces. Application of the steam engine to power blast bellows (indirectly by pumping water to a waterwheel) in Britain, beginning in 1743 and increasing in the 1750s, was a key factor in increasing the production of cast iron, which surged in the following decades. In addition to overcoming the limitation on water power, the steam-pumped-water powered blast gave higher furnace temperatures which allowed

1674-528: The 1840s to 1850s, the Stour Valley Railway built its Wolverhampton–Birmingham line along a route mostly parallel to the new main line canal. The railway company built an adjacent bridge to take its tracks under the road using one of the abutments from the canal bridge. The span is a masonry arch but the railway company built an iron parapet in keeping with the Galton Bridge. The bridge carried increasingly heavy vehicles for almost 150 years until

1736-452: The 1970s, when Roebuck Lane (the road which crosses the Galton Bridge and the adjacent Summit Bridge ) was bypassed by a road improvement scheme. A much wider road (the A4252) was built and the Galton Bridge was closed to vehicles but continues to carry pedestrians and cyclists. Instead of constructing a new bridge, the 1970s engineers partly filled in the cutting and built a concrete tunnel for

1798-414: The 19th refining the construction methods. The bridge is a single span of 150 ft (46 m), 26 ft (8 m) wide and 70 ft (20 m) above the canal. It consists of six cast-iron ribs, each made of seven segments, bolted together. The bridge is supported by tall brick abutments built into the valley sides. The deck plate is supported by X-shaped bracing in the spandrels . Telford added

1860-498: The Industrial Revolution, cast iron was also widely used for frame and other fixed parts of machinery, including spinning and later weaving machines in textile mills. Cast iron became widely used, and many towns had foundries producing industrial and agricultural machinery. Abutment The civil engineering term may also refer to the structure supporting one side of an arch , or masonry used to resist

1922-488: The alloy's composition. The eutectic carbides form as bundles of hollow hexagonal rods and grow perpendicular to the hexagonal basal plane. The hardness of these carbides are within the range of 1500-1800HV. Malleable iron starts as a white iron casting that is then heat treated for a day or two at about 950 °C (1,740 °F) and then cooled over a day or two. As a result, the carbon in iron carbide transforms into graphite and ferrite plus carbon. The slow process allows

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1984-410: The attached span across the railway. Cast-iron Cast iron is a class of iron – carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its carbon appears: white cast iron has its carbon combined into an iron carbide named cementite , which

2046-429: The benefit of what is called precipitation hardening (as in some steels, where much smaller cementite precipitates might inhibit [plastic deformation] by impeding the movement of dislocations through the pure iron ferrite matrix). Rather, they increase the bulk hardness of the cast iron simply by virtue of their own very high hardness and their substantial volume fraction, such that the bulk hardness can be approximated by

2108-537: The blast furnaces at Coalbrookdale. Other inventions followed, including one patented by Thomas Paine . Cast-iron bridges became commonplace as the Industrial Revolution gathered pace. Thomas Telford adopted the material for his bridge upstream at Buildwas , and then for Longdon-on-Tern Aqueduct , a canal trough aqueduct at Longdon-on-Tern on the Shrewsbury Canal . It was followed by

2170-539: The bolt holes were also cast and not drilled. Thus, because of casting's draft angle, the tension from the tie bars was placed on the hole's edge rather than being spread over the length of the hole. The replacement bridge was built in wrought iron and steel. Further bridge collapses occurred, however, culminating in the Norwood Junction rail accident of 1891. Thousands of cast-iron rail underbridges were eventually replaced by steel equivalents by 1900 owing to

2232-571: The canal, which was reduced in width. The new road, which runs parallel to the Galton Bridge, was named Telford Way and the canal tunnel named Galton Tunnel. The area around the bridge is sometimes known as the Galton Valley. The structure lends its name to the nearby Smethwick Galton Bridge railway station . The bridge underwent minor structural repair work in 1987 and was repainted in colour to enhance its features; before this, it had always been painted black. An inspection using ropes to access

2294-522: The carbon in white cast iron precipitates out of the melt as the metastable phase cementite , Fe 3 C, rather than graphite. The cementite which precipitates from the melt forms as relatively large particles. As the iron carbide precipitates out, it withdraws carbon from the original melt, moving the mixture toward one that is closer to eutectic , and the remaining phase is the lower iron-carbon austenite (which on cooling might transform to martensite ). These eutectic carbides are much too large to provide

2356-439: The carbon to separate as spheroidal particles as the material solidifies. The properties are similar to malleable iron, but parts can be cast with larger sections. Cast iron and wrought iron can be produced unintentionally when smelting copper using iron ore as a flux. The earliest cast-iron artifacts date to the 5th century BC, and were discovered by archaeologists in what is now modern Luhe County , Jiangsu in China during

2418-627: The cotton, hemp , or wool being spun. As a result, textile mills had an alarming propensity to burn down. The solution was to build them completely of non-combustible materials, and it was found convenient to provide the building with an iron frame, largely of cast iron, replacing flammable wood. The first such building was at Ditherington in Shrewsbury , Shropshire. Many other warehouses were built using cast-iron columns and beams, although faulty designs, flawed beams or overloading sometimes caused building collapses and structural failures. During

2480-695: The day, and he designed a new, straighter route (known as the New Main Line, the original canal becoming the Old Main Line) which significantly reduced the length of the canal. This scheme involved the excavation of an artificial valley through the high ground in Smethwick. The bridge was named after Samuel Tertius Galton , a local businessman and major investor in the Birmingham Canal Company. Three local roads were severed by

2542-599: The development of steel-framed skyscrapers. Cast iron was also used sometimes for decorative facades, especially in the United States, and the Soho district of New York has numerous examples. It was also used occasionally for complete prefabricated buildings, such as the historic Iron Building in Watervliet, New York . Another important use was in textile mills . The air in the mills contained flammable fibres from

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2604-520: The effects of sulfur, manganese is added, because the two form into manganese sulfide instead of iron sulfide. The manganese sulfide is lighter than the melt, so it tends to float out of the melt and into the slag . The amount of manganese required to neutralize sulfur is 1.7 × sulfur content + 0.3%. If more than this amount of manganese is added, then manganese carbide forms, which increases hardness and chilling , except in grey iron, where up to 1% of manganese increases strength and density. Nickel

2666-426: The highest single-span arch bridge in the world when it was built, 26 feet (7.9 metres) wide, and 150 feet (46 metres) long. The iron components were fabricated at the nearby Horseley Ironworks and assembled atop the masonry abutments . The design includes decorative lamp-posts and X-shaped bracing in the spandrels . In the 1840s, a railway bridge was built from one of the abutments, with a parapet in keeping with

2728-539: The lower edge in tension, where cast iron, like masonry , is very weak. Nevertheless, cast iron continued to be used in inappropriate structural ways, until the Tay Rail Bridge disaster of 1879 cast serious doubt on the use of the material. Crucial lugs for holding tie bars and struts in the Tay Bridge had been cast integral with the columns, and they failed in the early stages of the accident. In addition,

2790-434: The major obstacles on the route was a patch of high ground at Smethwick , roughly 4 miles (6.4 kilometres) north-west of Birmingham. The engineers had originally planned to tunnel through, but discovered that the ground conditions were not suitable. Thus, the canal was carried over the hill by a flight of locks . By the 1820s canal traffic had grown enormously and its narrowness was causing congestion. The summit at Smethwick

2852-478: The material, which he discovered could be used to create wider spans than had previously been possible using brick or stone. Cast iron is brittle under tension but strong under compression ; in bridge construction, it tended to be used in arch form. The world's first iron bridge opened in Shropshire fifty years before the Galton Bridge. Engineers including Telford spent the rest of the 18th century and much of

2914-406: The molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are then added to the melt before the final form is produced by casting . Cast iron is sometimes melted in a special type of blast furnace known as

2976-416: The original. The Galton Bridge carried traffic for over 140 years until it was bypassed by a new road, named Telford Way, in the 1970s, and now carries only pedestrians and cyclists. The bridge is one of six built by Telford that share common design features and the only one still standing without modification. It underwent minor repair work in the 1980s, after which it was repainted from its original black into

3038-418: The properties of malleable cast iron are more like those of mild steel . There is a limit to how large a part can be cast in malleable iron, as it is made from white cast iron. Developed in 1948, nodular or ductile cast iron has its graphite in the form of very tiny nodules with the graphite in the form of concentric layers forming the nodules. As a result, the properties of ductile cast iron are that of

3100-762: The relationship between wood and stone. Cast-iron beam bridges were used widely by the early railways, such as the Water Street Bridge in 1830 at the Manchester terminus of the Liverpool and Manchester Railway , but problems with its use became all too apparent when a new bridge carrying the Chester and Holyhead Railway across the River Dee in Chester collapsed killing five people in May 1847, less than

3162-475: The retention of carbon and the formation of those carbides. Nickel and copper increase strength and machinability, but do not change the amount of graphite formed. Carbon as graphite produces a softer iron, reduces shrinkage, lowers strength, and decreases density. Sulfur , largely a contaminant when present, forms iron sulfide , which prevents the formation of graphite and increases hardness . Sulfur makes molten cast iron viscous, which causes defects. To counter

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3224-501: The technique of producing cast-iron cannons, which, while heavier than the prevailing bronze cannons, were much cheaper and enabled England to arm her navy better. Cast-iron pots were made at many English blast furnaces at the time. In 1707, Abraham Darby patented a new method of making pots (and kettles) thinner and hence cheaper than those made by traditional methods. This meant that his Coalbrookdale furnaces became dominant as suppliers of pots, an activity in which they were joined in

3286-401: The top of the banks of the cutting would require substantial abutments which risked the stonework becoming waterlogged and bulging during heavy rain, whereas an iron span was lighter and required smaller abutments. Telford wrote that "the proportion of masonry is small, and produces variety by its appearance of lightness, which agreeably strikes every spectator." The Galton Bridge is the last of

3348-432: The underside in the 2000s established that the bridge was in excellent condition and that the 1980s paint work had survived well. The bridge is the responsibility of the Canal and River Trust (formerly British Waterways ). It has been a grade   I listed building , the highest of three grades, since 1971. Listed building status provides legal protection from demolition or modification. The list entry explicitly includes

3410-566: The use of higher lime ratios, enabling the conversion from charcoal (supplies of wood for which were inadequate) to coke. The ironmasters of the Weald continued producing cast irons until the 1760s, and armament was one of the main uses of irons after the Restoration . The use of cast iron for structural purposes began in the late 1770s, when Abraham Darby III built The Iron Bridge , although short beams had already been used, such as in

3472-518: The widespread concern about cast iron under bridges on the rail network in Britain. Cast-iron columns , pioneered in mill buildings, enabled architects to build multi-storey buildings without the enormously thick walls required for masonry buildings of any height. They also opened up floor spaces in factories, and sight lines in churches and auditoriums. By the mid 19th century, cast iron columns were common in warehouse and industrial buildings, combined with wrought or cast iron beams, eventually leading to

3534-426: The work, two of which were replaced with traditional masonry bridges, but Roebuck Lane was to cross the cutting at its widest and deepest point. Like all the bridges on the new route, it needed to span the canal without obstructing the waterway or the towpaths . Hence, Telford considered a lighter structure was necessary. Telford was a pioneer in the use of cast iron and became famed for his bridges and aqueducts using

3596-514: Was also produced. Numerous testimonies were made by early European missionaries of the Luba people pouring cast iron into molds to make hoes. These technological innovations were accomplished without the invention of the blast furnace which was the prerequisite for the deployment of such innovations in Europe and Asia. The technology of cast iron was transferred to the West from China. Al-Qazvini in

3658-410: Was more desirable, cast iron was cheaper and thus was more commonly used for implements in ancient China, while wrought iron or steel was used for weapons. The Chinese developed a method of annealing cast iron by keeping hot castings in an oxidizing atmosphere for a week or longer in order to burn off some carbon near the surface in order to keep the surface layer from being too brittle. Deep within

3720-418: Was short and bordered by locks at each end; as a result, it was common for long queues of boats to form at either end and fights often broke out among boat crews. Improvements had been mooted for years, though the immediate catalyst for investment was a proposal for a railway connecting Birmingham to Liverpool via Wolverhampton. The canal proprietors consulted Thomas Telford , the most eminent canal engineer of

3782-522: Was used in ancient China to mass-produce weaponry for warfare, as well as agriculture and architecture. During the 15th century AD, cast iron became utilized for cannons and shot in Burgundy , France, and in England during the Reformation . The amounts of cast iron used for cannons required large-scale production. The first cast-iron bridge was built during the 1770s by Abraham Darby III , and

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3844-486: Was washed away in a flood and Mythe and Holt Fleet bridges were both strengthened with modern materials in the 20th century. The others are Craigellachie Bridge (1814) in north-eastern Scotland, and Waterloo Bridge (1816) in Betws-y-Coed , North Wales, both also strengthened in the 20th century. The Galton Bridge originally held commanding views of the valley on either side, but these are now obstructed. The bridge

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