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84-821: Henry Grissell (4 July 1817 – 31 January 1883), sometimes known as "Iron Henry", was an English foundry -man who was responsible for the ironwork in a number of prestigious buildings in England, Russia, Austria, and Egypt. Henry Grissell was born in London to Thomas de la Garde Grissell, who worked with the East India Company . He started work with John Joseph Bramah, of the Bramah company, known for his intricate castings and metal work. Grissell started his own business in partnership with his brother, Martin De La Garde Grissell, at

168-418: A pattern is made in the shape of the desired part. Simple designs can be made in a single piece or solid pattern. More complex designs are made in two parts, called split patterns. A split pattern has a top or upper section, called a cope, and a bottom or lower section called a drag. Both solid and split patterns can have cores inserted to complete the final part shape. Cores are used to create hollow areas in

252-431: A base. Care is taken to layer the scrap in the basket to ensure good furnace operation; heavy melt is placed on top of a light layer of protective shred, on top of which is placed more shred. These layers should be present in the furnace after charging. After loading, the basket may pass to a scrap pre-heater, which uses hot furnace off-gases to heat the scrap and recover energy, increasing plant efficiency. The scrap basket

336-431: A capacity of only a few dozen grams. Industrial electric arc furnace temperatures can reach 1,800 °C (3,300 °F), while laboratory units can exceed 3,000 °C (5,400 °F). In electric arc furnaces, the charge material (the material entered into the furnace for heating, not to be confused with electric charge ) is directly exposed to an electric arc, and the current from the electrode terminals passes through

420-403: A continuous, rather than batch, basis. Continuous-process furnaces may also use paste-type, Søderberg electrodes to prevent interruptions from electrode changes. Such a furnace is known as a submerged arc furnace , because the electrode tips are buried in the slag/charge, and arcing occurs through the slag, between the matte and the electrode. The casing and casing fins of the electrode melt

504-400: A finished product. More and more, finishing processes are being performed by robotic machines, which eliminate the need for a human to physically grind or break parting lines, gating material, or feeders. Machines can reduce risk of injury to workers and lower costs for consumables — while also increasing productivity. They also limit the potential for human error and increase repeatability in

588-566: A greater affinity for oxygen. Metals that have a poorer affinity for oxygen than iron, such as nickel and copper , cannot be removed through oxidation and must be controlled through scrap chemistry alone, such as introducing the direct reduced iron and pig iron mentioned earlier. A foaming slag is maintained throughout, and often overflows the furnace to pour out of the slag door into the slag pit. Temperature sampling and chemical sampling take place via automatic lances. Oxygen and carbon can be automatically measured via special probes that dip into

672-445: A material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing , case-hardening , precipitation strengthening , tempering , and quenching . Although

756-399: A modern shop such a furnace would be expected to produce a quantity of 80 tonnes of liquid steel in approximately 50 minutes from charging with cold scrap to tapping the furnace. In comparison, basic oxygen furnaces can have a capacity of 150–300 tonnes per batch, or "heat", and can produce a heat in 30–40 minutes. Enormous variations exist in furnace design details and operation, depending on

840-420: A particular metal and have furnaces dedicated to these metals. For example, an iron foundry (for cast iron) may use a cupola , induction furnace, or EAF, while a steel foundry will use an EAF or induction furnace. Bronze or brass foundries use crucible furnaces or induction furnaces. Most aluminium foundries use either electric resistance or gas heated crucible furnaces or reverberatory furnaces. Degassing

924-437: A pattern of hot and cold-spots around the hearth perimeter, with the cold-spots located between the electrodes. Modern furnaces mount oxygen-fuel burners in the sidewall and use them to provide chemical energy to the cold-spots, making the heating of the steel more uniform. Additional chemical energy is provided by injecting oxygen and carbon into the furnace; historically this was done through lances (hollow mild-steel tubes ) in

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1008-404: A scrap bay, located next to the melt shop. Scrap generally comes in two main grades: shred ( whitegoods , cars and other objects made of similar light-gauge steel) and heavy melt (large slabs and beams), along with some direct reduced iron (DRI) or pig iron for chemical balance. Some furnaces melt almost 100% DRI. The scrap is loaded into large buckets called baskets, with "clamshell" doors for

1092-411: A tonne of scrap steel is 300 kWh (1.09 GJ) (melting point 1,520 °C (2,768 °F)). Therefore, a 300-tonne, 300 MVA EAF will require approximately 132 MWh of energy to melt the steel, and a "power-on time" (the time that steel is being melted with an arc) of approximately 37 minutes. Electric arc steelmaking is only economical where there is plentiful, reliable electricity, with

1176-410: A vacuum or pressurized gas. Many modern foundries use robots or automatic pouring machines to pour molten metal. Traditionally, molds were poured by hand using ladles . The solidified metal component is then removed from its mold. Where the mold is sand based, this can be done by shaking or tumbling. This frees the casting from the sand, which is still attached to the metal runners and gates — which are

1260-410: A well-developed electrical grid. In many locations, mills operate during off-peak hours when utilities have surplus power generating capacity and the price of electricity is less. This compares very favourably with energy consumption of global steel production by all methods estimated at some 5,555 kWh (20 GJ) per tonne (1 gigajoule is equal to approximately 270 kWh). Scrap metal is delivered to

1344-426: Is iron oxide from steel combusting with the injected oxygen. Later in the heat, carbon (in the form of coke or coal ) is injected into this slag layer, reacting with the iron oxide to form metallic iron and carbon monoxide gas, which then causes the slag to foam , allowing greater thermal efficiency , and better arc stability and electrical efficiency . The slag blanket also covers the arcs, preventing damage to

1428-409: Is a complex process, and the design can be optimized based on multiple factors. Furnaces in foundries can be any size, ranging from small ones used to melt precious metals to furnaces weighing several tons, designed to melt hundreds of pounds of scrap at one time. They are designed according to the type of metals that are to be melted. Furnaces must also be designed based on the fuel being used to produce

1512-414: Is a process that may be required to reduce the amount of hydrogen present in a batch of molten metal. Gases can form in metal castings in one of two ways: Hydrogen is a common contaminant for most cast metals. It forms as a result of material reactions or from water vapor or machine lubricants. If the hydrogen concentration in the melt is too high, the resulting casting will be porous; the hydrogen will exit

1596-448: Is another form of recycling. In metalworking , casting involves pouring liquid metal into a mold , which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods. Melting

1680-406: Is called "tapping". Originally, all steelmaking furnaces had a tapping spout closed with refractory that washed out when the furnace was tilted, but often modern furnaces have an eccentric bottom tap-hole (EBT) to reduce inclusion of nitrogen and slag in the liquid steel. These furnaces have a taphole that passes vertically through the hearth and shell, and is set off-centre in the narrow "nose" of

1764-585: Is cleaned using a blasting process. This means a granular media will be propelled against the surface of the casting to mechanically knock away the adhering sand. The media may be blown with compressed air, or may be hurled using a shot wheel. The cleaning media strikes the casting surface at high velocity to dislodge the mold remnants (for example, sand, slag) from the casting surface. Numerous materials may be used to clean cast surfaces, including steel, iron, other metal alloys, aluminium oxides, glass beads, walnut shells, baking powder, and many others. The blasting media

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1848-600: Is filled with sand at the completion of tapping. For a 90-tonne, medium-power furnace, the whole process will usually take about 60–70 minutes from the tapping of one heat to the tapping of the next (the tap-to-tap time). The furnace is completely emptied of steel and slag on a regular basis so that an inspection of the refractories can be made and larger repairs made if necessary. As the refractories are often made from calcined carbonates , they are extremely susceptible to hydration from water, so any suspected leaks from water-cooled components are treated extremely seriously, beyond

1932-626: Is flexibility: while blast furnaces cannot vary their production by much and can remain in operation for years at a time, EAFs can be rapidly started and stopped, allowing the steel mill to vary production according to demand. Although steelmaking arc furnaces generally use scrap steel as their primary feedstock, if hot metal from a blast furnace or direct-reduced iron is available economically, these can also be used as furnace feed. As EAFs require large amounts of electrical power, many companies schedule their operations to take advantage of off-peak electricity pricing . A typical steelmaking arc furnace

2016-487: Is happening inside the mold or die during the casting process. Electric arc furnace An electric arc furnace ( EAF ) is a furnace that heats material by means of an electric arc . Industrial arc furnaces range in size from small units of approximately one-tonne capacity (used in foundries for producing cast iron products) up to about 400-tonne units used for secondary steelmaking . Arc furnaces used in research laboratories and by dentists may have

2100-420: Is left in the furnace in order to form a "hot heel", which helps preheat the next charge of scrap and accelerate its meltdown. During and after tapping, the furnace is "turned around": the slag door is cleaned of solidified slag, the visible refractories are inspected and water-cooled components checked for leaks, and electrodes are inspected for damage or lengthened through the addition of new segments. The taphole

2184-408: Is material from other forming processes such as punching , forging , or machining . Internal scrap consists of gates , risers , defective castings, and other extraneous metal oddments produced within the facility. The process includes melting the charge, refining the melt, adjusting the melt chemistry and tapping into a transport vessel. Refining is done to remove harmful gases and elements from

2268-418: Is performed in a furnace . Virgin material, external scrap, internal scrap, and alloying elements are used to charge the furnace. Virgin material refers to commercially pure forms of the primary metal used to form a particular alloy . Alloying elements are either pure forms of an alloying element, like electrolytic nickel , or alloys of limited composition, such as ferroalloys or master alloys. External scrap

2352-470: Is provided by wall-mounted oxygen-fuel burners. Both processes accelerate scrap meltdown. Supersonic nozzles enable oxygen jets to penetrate foaming slag and reach the liquid bath. An important part of steelmaking is the formation of slag , which floats on the surface of the molten steel. Slag usually consists of metal oxides , and acts as a destination for oxidised impurities, as a thermal blanket (stopping excessive heat loss) and helping to reduce erosion of

2436-444: Is selected to develop the color and reflectance of the cast surface. Terms used to describe this process include cleaning, bead blasting, and sand blasting . Shot peening may be used to further work-harden and finish the surface. The final step in the process of casting usually involves grinding, sanding, or machining the component in order to achieve the desired dimensional accuracies, physical shape, and surface finish. Removing

2520-571: Is significantly lower than the conventional production route via blast furnaces and the basic oxygen furnace, which produces 2.9 tons CO2 per ton of steel produced. Although the modern electric arc furnace is a highly efficient recycler of steel scrap , operation of an arc furnace shop can have adverse environmental effects. Much of the capital cost of a new installation will be devoted to systems intended to reduce these effects, which include: Since EAF steelmaking mainly use recycled materials like scrap iron and scrap steel, as their composition varies

2604-503: Is that these processes have better dimensional capability and repeatability than many casting processes. However, it is not uncommon today for castings to be used without machining. A few foundries provide other services before shipping cast products to their customers. It is common to paint castings to prevent corrosion and improve visual appeal. Some foundries assemble castings into complete machines or sub-assemblies. Other foundries weld multiple castings or wrought metals together to form

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2688-422: Is the highest efficiency cooling method. A spray cooling piece of equipment can be relined almost endlessly. Equipment that lasts 20 years is the norm. While a tubular leak is immediately noticed in an operating furnace due to the pressure loss alarms on the panels, at this time there exists no immediate way of detecting a very small volume spray cooling leak. These typically hide behind slag coverage and can hydrate

2772-495: Is the source of steel for a mini-mill, which may make bars or strip product. Mini-mills can be sited relatively near the markets for steel products, so the transport requirements are less than for an integrated mill, which would commonly be sited near a harbor for better access to shipping. Depending on the proportions of steel scrap, DRI and pig iron used, electric arc furnace steelmaking can result in carbon dioxide emissions as low as 0.6 tons CO 2 per ton of steel produced, which

2856-456: Is then taken to the melt shop, the roof is swung off the furnace, and the furnace is charged with scrap from the basket. Charging is one of the more dangerous operations for the EAF operators. A lot of potential energy is released by the tonnes of falling metal; any liquid metal in the furnace is often displaced upwards and outwards by the solid scrap, and the grease and dust on the scrap is ignited if

2940-411: Is too conductive to form an effective heat-generating resistance. Amateurs have constructed a variety of arc furnaces, often based on electric arc welding kits contained by silica blocks or flower pots. Though crude, these simple furnaces can melt a wide range of materials, create calcium carbide , and more. Smaller arc furnaces may be adequately cooled by circulation of air over structural elements of

3024-410: Is typically used for iron and steel. There are various types of equipment that can measure the presence of hydrogen. Alternatively, the presence of hydrogen can be measured by determining the density of a metal sample. In cases where porosity still remains present after the degassing process, porosity sealing can be accomplished through a process called metal impregnating . In the casting process,

3108-457: Is used, as well as less electrical harmonics and other similar problems. The size of DC arc furnaces is limited by the current carrying capacity of available electrodes, and the maximum allowable voltage. Maintenance of the conductive furnace hearth is a bottleneck in extended operation of a DC arc furnace. In a steel plant, a ladle furnace (LF) is used to maintain the temperature of liquid steel during processing after tapping from EAF or to change

3192-625: The Houses of Parliament and the new museum at South Kensington . He also made the gates for Sir William Tite 's Royal Exchange , the gates and railings round Buckingham Palace and at the British Museum . He cast all the Type 2 Coal Tax posts – about 200 of them. Another brother, Thomas Grissell , was a major public works contractor, with cousin Henry Peto. After the banking crisis of 1866, Henry closed

3276-405: The refractory lining. For a furnace with basic refractories, which includes most carbon steel -producing furnaces, the usual slag formers are calcium oxide (CaO, in the form of burnt lime ) and magnesium oxide (MgO, in the form of dolomite and magnesite ). These slag formers are either charged with the scrap, or blown into the furnace during meltdown. Another major component of EAF slag

3360-536: The Eastern US, the companies that followed them into mini-mill operations concentrated on local markets for long products, where the EAF allowed the plants to vary production according to local demand. This pattern was followed globally, with EAF steel production primarily used for long products, while integrated mills, using blast furnaces and basic oxygen furnaces , cornered the markets for "flat products"— sheet steel and heavier steel plate. In 1987, Nucor expanded into

3444-831: The Regent's Canal Ironworks, Eagle Wharf Road, as ironfounders and contractors in about 1841. Martin left the partnership in 1858. They worked with the major engineers of the time, including Robert Stephenson , Bidder, Walker & Burges, and Sir William Cubitt . The company made the ironwork for some major bridges, including at the river Nene, Sutton, Lincolnshire, Great Yarmouth , and the Nile in Egypt, as well as works in Portsmouth and Devonport dockyards. Overseas jobs included waterworks at Vienna , Leipzig , Russia , and various lighthouses. They also made ironwork for Covent Garden Opera House , for some of

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3528-644: The alloy composition. The ladle is used for the first purpose when there is a delay later in the steelmaking process. The ladle furnace consists of a refractory roof, a heating system, and, when applicable, a provision for injecting argon gas into the bottom of the melt for stirring. Unlike a scrap melting furnace, a ladle furnace does not have a tilting or scrap-charging mechanism. Electric arc furnaces are also used for production of calcium carbide , ferroalloys , and other non-ferrous alloys , and for production of phosphorus . Furnaces for these services are physically different from steel-making furnaces and may operate on

3612-615: The arc type. The first successful and operational furnace was invented by James Burgess Readman in Edinburgh , Scotland, in 1888 and patented in 1889. This was specifically for the creation of phosphorus . Further electric arc furnaces were developed by Paul Héroult , of France , with a commercial plant established in the United States in 1907. The Sanderson brothers formed The Sanderson Brothers Steel Co. in Syracuse, New York, installing

3696-411: The arcs. Once the electrodes have reached the heavy melt at the base of the furnace and the arcs are shielded by the scrap, the voltage can be increased and the electrodes raised slightly, lengthening the arcs and increasing power to the melt. This enables a molten pool to form more rapidly, reducing tap-to-tap times. Oxygen is blown into the scrap, combusting or cutting the steel, and extra chemical heat

3780-612: The bath. The Girod furnace is similar to the Héroult furnace . While EAFs were widely used in World War II for production of alloy steels, it was only later that electric steelmaking began to expand. The low capital cost for a mini-mill —around US$ 140–200 per ton of annual installed capacity, compared with US$ 1,000 per ton of annual installed capacity for an integrated steel mill —allowed mills to be quickly established in war-ravaged Europe, and also allowed them to successfully compete with

3864-504: The big United States steelmakers, such as Bethlehem Steel and U.S. Steel , for low-cost, carbon steel "long products" ( structural steel , rod and bar, wire , and fasteners ) in the U.S. market. When Nucor —now one of the largest steel producers in the US — entered the market for long steel products in 1969, they used a mini-mill with an EAF as its steelmaking furnace, soon followed by other manufacturers. While Nucor expanded rapidly in

3948-402: The bus tubes or arms with the transformer located adjacent to the furnace. The transformer is installed in a vault and is cooled by pump-circulated transformer oil, with the oil being cooled by water via heat exchangers. The furnace is built on a tilting platform so that the liquid steel can be poured into another vessel for transport. The operation of tilting the furnace to pour molten steel

4032-501: The casting with a sledge hammer or specially designed knockout machinery. Risers must usually be removed using a cutting method (see above) but some newer methods of riser removal use knockoff machinery with special designs incorporated into the riser neck geometry that allow the riser to break off at the right place. The gating system required to produce castings in a mold yields leftover metal — including heads, risers, and sprue (sometimes collectively called sprue) — that can exceed 50% of

4116-406: The channels through which the molten metal traveled to reach the component itself. Degating is the removal of the heads, runners, gates, and risers from the casting. Runners, gates, and risers may be removed using cutting torches , bandsaws , or ceramic cutoff blades. For some metal types, and with some gating system designs, the sprue, runners, and gates can be removed by breaking them away from

4200-461: The charge and by the radiant energy evolved by the arc. The electric arc temperature reaches around 3,000 °C (5,400 °F), thus causing the lower sections of the electrodes to glow incandescently when in operation. The electrodes are automatically raised and lowered by a positioning system, which may use either electric winch hoists or hydraulic cylinders . The regulating system maintains approximately constant current and power input during

4284-472: The charge material. Arc furnaces differ from induction furnaces , in which the charge is heated instead by eddy currents . In the 19th century, a number of people had employed an electric arc to melt iron . Sir Humphry Davy conducted an experimental demonstration in 1810; welding was investigated by Pepys in 1815; Pinchon attempted to create an electrothermic furnace in 1853; and, in 1878–79, Sir William Siemens took out patents for electric furnaces of

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4368-541: The desired temperature. For low temperature melting point alloys, such as zinc or tin, melting furnaces may reach around 500 °C (932 °F). Electricity, propane, or natural gas are usually used to achieve these temperatures. For high melting point alloys such as steel or nickel-based alloys, the furnace must be designed for temperatures over 1,600 °C (2,910 °F). The fuel used to reach these high temperatures can be electricity (as employed in electric arc furnaces ) or coke . The majority of foundries specialize in

4452-424: The egg-shaped hearth. It is filled with refractory sand, such as olivine , when it is closed off. Modern plants may have two shells with a single set of electrodes that can be transferred between the two; one shell preheats scrap while the other shell is utilised for meltdown. Other DC-based furnaces have a similar arrangement, but have electrodes for each shell and one set of electronics. AC furnaces usually exhibit

4536-435: The electrode paste through electrical current passing through the electrode casing and heat from the furnace. A steelmaking arc furnace, by comparison, arcs in the open. The key is the electrical resistance , which is what generates the heat required: the resistance in a steelmaking furnace is the atmosphere, while in a submerged-arc furnace, the slag (or charge) supplies the resistance. The liquid metal formed in either furnace

4620-623: The end product and local conditions, as well as ongoing research to improve furnace efficiency. The largest scrap-only furnace (in terms of tapping weight and transformer rating) is a DC furnace operated by Tokyo Steel in Japan, with a tap weight of 420 tonnes and fed by eight 32 MVA transformers for 256 MVA total power. To produce a ton of steel in an electric arc furnace requires approximately 400 kilowatt-hours (1.44 gigajoules ) per short ton or about 440 kWh (1.6 GJ) per tonne . The theoretical minimum amount of energy required to melt

4704-487: The entire casting manufacturing route. Casting process simulation was initially developed at universities starting from the early ' 70s , mainly in Europe and in the U.S. , and is regarded as the most important innovation in casting technology over the last 50 years. Since the late ' 80s , commercial programs (such as PoligonSoft, AutoCAST and Magma) are available which make it possible for foundries to gain new insight into what

4788-435: The first electric arc furnace in the U.S. This furnace is now on display at Station Square, Pittsburgh, Pennsylvania. Initially "electric steel" produced by an electric arc furnace was a specialty product for such uses as machine tools and spring steel . Arc furnaces were also used to prepare calcium carbide for use in carbide lamps . The Stassano electric furnace is an arc type furnace that usually rotates to mix

4872-445: The flat products market, still using the EAF production method. An electric arc furnace used for steelmaking consists of a refractory -lined vessel, usually water-cooled in larger sizes, covered with a retractable roof, and through which one or more graphite electrodes enter the furnace. The furnace is primarily split into three sections: The hearth may be hemispherical in shape, or in an eccentric bottom tapping furnace (see below),

4956-669: The foundry and developed his interests in Scandinavian timber. He died in 1883 at his home in Montagu Square and was interred at West Norwood Cemetery in an elaborate Gothic tomb made of iron, constructed initially for his father. Foundry Foundries are one of the largest contributors to the manufacturing recycling movement, melting and recasting millions of tons of scrap metal every year to create new durable goods. Moreover, many foundries use sand in their molding process. These foundries often use, recondition, and reuse sand, which

5040-442: The furnace is hot, resulting in a fireball erupting. In some twin-shell furnaces, the scrap is charged into the second shell while the first is being melted down, and pre-heated with off-gas from the active shell. Other operations are continuous charging—pre-heating scrap on a conveyor belt, which then discharges the scrap into the furnace proper, or charging the scrap from a shaft set above the furnace, with off-gases directed through

5124-545: The furnace roof and sidewalls from radiant heat. Once the initial scrap charge has been melted down, another bucket of scrap can be charged into the furnace, although EAF development is moving towards single-charge designs. The scrap-charging and meltdown process can be repeated as many times as necessary to reach the required heat weight - the number of charges is dependent on the density of scrap; lower-density scrap means more charges. After all scrap charges have completely melted, refining operations take place to check and correct

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5208-435: The furnace, or are fixed to the raised platform. A typical alternating current furnace is powered by a three-phase electrical supply , and therefore has three electrodes. Electrodes are round in section, and typically in segments with threaded couplings, so that as the electrodes wear, new segments can be added. The arc forms between the charged material and the electrode; the charge is heated both by current passing through

5292-417: The hearth has the shape of a halved egg. In modern meltshops, the furnace is often raised off the ground floor, so that ladles and slag pots can easily be maneuvered under either end of the furnace. Separate from the furnace structure is the electrode support and electrical system, and the tilting platform on which the furnace rests. Two configurations are possible: the electrode supports and the roof tilt with

5376-417: The immediate concern of potential steam explosions . Excessive refractory wear can lead to breakouts, where the liquid metal and slag penetrate the refractory and furnace shell and escape into the surrounding areas. The use of EAFs allows steel to be made from a 100% scrap metal feedstock. This greatly reduces the energy required to make steel when compared with primary steelmaking from ores. Another benefit

5460-401: The ladle. For some special steel grades, including stainless steel, the slag is poured into the ladle as well, to be treated at the ladle furnace to recover valuable alloying elements. During tapping some alloy additions are introduced into the metal stream, and more fluxes such as lime are added on top of the ladle to begin building a new slag layer. Often, a few tonnes of liquid steel and slag

5544-426: The melting of the charge, even though scrap may move under the electrodes as it melts. The mast arms holding the electrodes can either carry heavy busbars (which may be hollow water-cooled copper pipes carrying current to the electrode clamps) or be "hot arms", where the whole arm carries the current, increasing efficiency. Hot arms can be made from copper-clad steel or aluminium . Large water-cooled cables connect

5628-419: The metal required to pour a full mold. Since this metal must be remelted as salvage, the yield of a particular gating configuration becomes an important economic consideration when designing various gating schemes, to minimize the cost of excess sprue, and thus overall melting costs. Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of

5712-520: The metal. Furnaces are refractory-lined vessels that contain the material to be melted and provide the energy to melt it. Modern furnace types include electric arc furnaces (EAF), induction furnaces , cupolas , reverberatory , and crucible furnaces. Furnace choice is dependent on the alloy system quantities produced. For ferrous materials EAFs, cupolas, and induction furnaces are commonly used. Reverberatory and crucible furnaces are common for producing aluminium, bronze, and brass castings. Furnace design

5796-416: The mold that would otherwise be impossible to achieve. Where the cope and drag separates is called the parting line . When making a pattern it is best to taper the edges so that the pattern can be removed without breaking the mold. This is called draft . The opposite of draft is an undercut where there is part of the pattern under the mold material, making it impossible to remove the pattern without damaging

5880-415: The mold. The pattern is made of wax, wood, plastic, or metal. The molds are constructed by several different processes dependent upon the type of foundry, metal to be poured, quantity of parts to be produced, size of the casting, and complexity of the casting. These mold processes include: In a foundry, molten metal is poured into molds . Pouring can be accomplished with gravity, or it may be assisted with

5964-458: The molten metal to avoid casting defects. Material is added during the melting process to bring the final chemistry within a specific range specified by industry and/or internal standards. Certain fluxes may be used to separate the metal from slag and/or dross and degassers are used to remove dissolved gas from metals that readily dissolve in gasses. During the tap, final chemistry adjustments are made. Several specialised furnaces are used to heat

6048-490: The molten solution, leaving minuscule air pockets, as the metal cools and solidifies. Porosity often seriously deteriorates the mechanical properties of the metal. An efficient way of removing hydrogen from the melt is to bubble a dry, insoluble gas through the melt by purging or agitation. When the bubbles go up in the melt, they catch the dissolved hydrogen and bring it to the surface. Chlorine, nitrogen, helium and argon are often used to degas non-ferrous metals. Carbon monoxide

6132-429: The quality of grinding. Casting processes simulation uses numerical methods to calculate cast component quality considering mold filling, solidification and cooling, and provides a quantitative prediction of casting mechanical properties, thermal stresses and distortion. Simulation accurately describes a cast component's quality up-front before production starts. The casting rigging can be designed with respect to

6216-431: The quality of power for other customers; flicker and harmonic distortion are common power system side-effects of arc furnace operation. For steelmaking, direct current (DC) arc furnaces are used, with a single electrode in the roof and the current return through a conductive bottom lining or conductive pins in the base. The advantage of DC is lower electrode consumption per ton of steel produced, since only one electrode

6300-472: The refractory in the hearth, leading to a break out of molten metal or in the worst case a steam explosion. A plasma arc furnace (PAF) uses plasma torches instead of graphite electrodes. Each of these torches has a casing with a nozzle and axial tubing for feeding a plasma-forming gas (either nitrogen or argon) and a burnable cylindrical graphite electrode within the tubing. Such furnaces can be called plasma arc melt (PAM) furnaces; they are used extensively in

6384-477: The remaining gate material, called a gate stub, is usually done using a grinder or sander . These processes are used because their material removal rates are slow enough to control the amount of material being removed. These steps are done prior to any final machining. After grinding, any surfaces that require tight dimensional control are machined. Many castings are machined in CNC milling centers. The reason for this

6468-413: The required component properties. This has benefits beyond a reduction in pre-production sampling, as the precise layout of the complete casting system also leads to energy , material, and tooling savings. The software supports the user in component design, the determination of melting practice and casting methoding through to pattern and mold making, heat treatment , and finishing. This saves costs along

6552-404: The resulting EAF slag and EAF dust can be toxic. EAF dust is collected by air pollution control equipment. It is called collected dust and usually contains heavy metals, such as zinc, lead and dioxins, etc. It is categorized as hazardous industrial waste and disposal is regulated. Because of the very dynamic quality of the arc furnace load, power systems may require technical measures to maintain

6636-451: The shaft. Other furnaces can be charged with hot (molten) metal from other operations. After charging, the roof is swung back over the furnace and meltdown commences. The electrodes are lowered onto the scrap, an arc is struck and the electrodes are then set to bore into the layer of shred at the top of the furnace. Lower voltages are selected for this first part of the operation to protect the roof and walls from excessive heat and damage from

6720-419: The shell and roof, but larger installations require intensive forced cooling to maintain the structure within safe operating limits. The furnace shell and roof may be cooled either by water circulated through pipes which form a panel, or by water sprayed on the panel elements. Tubular panels may be replaced when they become cracked or reach their thermal stress life cycle. Spray cooling is the most economical and

6804-400: The slag door, but now this is mainly done through wall-mounted injection units that combine the oxygen-fuel burners and the oxygen or carbon injection systems into one unit. A mid-sized modern steelmaking furnace would have a transformer rated about 60,000,000 volt-amperes (60 MVA), with a secondary voltage between 400 and 900 volts and a secondary current in excess of 44,000 amperes. In

6888-410: The steel chemistry and superheat the melt above its freezing temperature in preparation for tapping. More slag formers are introduced and more oxygen is blown into the bath, burning out impurities such as silicon , sulfur , phosphorus , aluminium , manganese , and calcium , and removing their oxides to the slag. Removal of carbon takes place after these elements have burnt out first, as they have

6972-443: The steel, but for all other elements, a "chill" sample — a small, solidified sample of the steel — is analysed on an arc-emission spectrometer . Once the temperature and chemistry are correct, the steel is tapped out into a preheated ladle through tilting the furnace. For plain-carbon steel furnaces, as soon as slag is detected during tapping the furnace is rapidly tilted back towards the deslagging side, minimising slag carryover into

7056-407: The term "heat treatment" applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding. After degating and heat treating, sand or other molding media may remain adhered to the casting. To remove any mold remnants, the surface

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