Electric arc furnace

An electric arc furnace (EAF) is a furnace that heats charged material by means of an electric arc.

Industrial arc furnaces range in size from small units of approximately one ton capacity (used in foundries for producing cast iron products) up to about 400 ton units used for secondary steelmaking. Arc furnaces used in research laboratories and by dentists may have a capacity of only a few dozen grams. Industrial electric arc furnace temperatures can be up to 1,800 °C (3,272 °F), while laboratory units can exceed 3,000 °C (5,432 °F).

Arc furnaces differ from induction furnaces in that the charge material is directly exposed to an electric arc and the current in the furnace terminals passes through the charged material.

Fotothek df n-08 0000383
An electric arc furnace (the large cylinder) being tapped
Melt Down uddeholm
Rendering of exterior and interior of an electric arc furnace.

History

In the 19th century, a number of men 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 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.[1][2]

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 the first electric arc furnace in the U.S. This furnace is now on display at Station Square, Pittsburgh, Pennsylvania.[3]

Heroult refining furnace Transversal view Stoughton
A schematic cross section through a Heroult arc furnace. E is an electrode (only one shown), raised and lowered by the rack and pinion drive R and S. The interior is lined with refractory brick H, and K denotes the bottom lining. A door at A allows access to the interior. The furnace shell rests on rockers to allow it to be tilted for tapping.

Initially "electric steel" 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 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 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 U.S.[4]—decided to enter the long products market in 1969, they chose to start up a mini-mill, with an EAF as its steelmaking furnace, soon followed by other manufacturers. Whilst Nucor expanded rapidly in the Eastern U.S., the companies that followed them into mini-mill operations concentrated on local markets for long products, where the use of an EAF allowed the plants to vary production according to local demand. This pattern was also 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 made the decision to expand into the flat products market, still using the EAF production method.[5]

Construction

Electric Arc Furnace
A schematic cross-section through an EAF. Three electrodes (yellow), molten bath (gold), tapping spout at left, refractory brick movable roof, brick shell, and a refractory-lined bowl-shaped hearth.

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.[6] The furnace is primarily split into three sections:

  • the shell, which consists of the sidewalls and lower steel "bowl";
  • the hearth, which consists of the refractory that lines the lower bowl;
  • the roof, which may be refractory-lined or water-cooled, and can be shaped as a section of a sphere, or as a frustum (conical section). The roof also supports the refractory delta in its centre, through which one or more graphite electrodes enter.

The hearth may be hemispherical in shape, or in an eccentric bottom tapping furnace (see below), 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 the furnace, or are fixed to the raised platform.

Fotothek df n-32 0000122 Metallurge für Hüttentechnik
The roof of an arc furnace removed, showing the three electrodes

A typical alternating current furnace is powered by a three-phase electrical supply and therefore has three electrodes.[7] 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 the charge and by the radiant energy evolved by the arc. The electric arc temperature reaches around 3000 °C (5000 °F), thus causing the lower sections of the electrodes to glow incandescently when in operation.[8] 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 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 the bus tubes or arms with the transformer located adjacent to the furnace. The transformer is installed in a vault and is water-cooled. [6]

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 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 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 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[9]) in the slag door, 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 a modern shop such a furnace would be expected to produce a quantity of 80 metric 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 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 metric tonnes and fed by eight 32MVA transformers for 256MVA total power.

To produce a ton of steel in an electric arc furnace requires approximately 400 kilowatt-hours per short ton or about 440 kWh per metric tonne; the theoretical minimum amount of energy required to melt a tonne of scrap steel is 300 kWh (melting point 1520 °C/2768 °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 electricity, with 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.

Operation

Allegheny Ludlum steel furnace
An arc furnace pouring out steel into a small ladle car. The transformer vault can be seen at the right side of the picture. For scale, note the operator standing on the platform at upper left. This is a 1941-era photograph and so does not have the extensive dust collection system that a modern installation would have, nor is the operator wearing a hard hat or dust mask.

Scrap metal is delivered to 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 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 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 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 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 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 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 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 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 the furnace roof and sidewalls from radiant heat.

Once the scrap has completely melted down and a flat bath is reached, another bucket of scrap can be charged into the furnace and melted down, although EAF development is moving towards single-charge designs. After the second charge is completely melted, refining operations take place to check and correct 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 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 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 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 lime is added on top of the ladle to begin building a new slag layer. Often, a few tonnes of liquid steel and slag 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 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 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.

Advantages for steelmaking

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 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 is the source of steel for a mini-mill, which may make bars or strip product. Mini-mills can be sited relatively near to the markets for steel products, and the transport requirements are less than for an integrated mill, which would commonly be sited near a harbour for access to shipping.

Environmental issues

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:

  • Enclosures to reduce high sound levels
  • Dust collector for furnace off-gas
  • Slag production
  • Cooling water demand
  • Heavy truck traffic for scrap, materials handling, and product
  • Environmental effects of electricity generation

Because of the very dynamic quality of the arc furnace load, power systems may require technical measures to maintain the quality of power for other customers; flicker and harmonic distortion are common side-effects of arc furnace operation on a power system. For this reason the power station should be located as close to the EA furnaces as possible.

Other electric arc furnaces

Ladle refining uddeholm
Rendering of a ladle furnace, a variation of the electric arc furnace used for keeping molten steel hot

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 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 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 a continuous, rather than batch, basis. Continuous process furnaces may also use paste-type, Søderberg electrodes to prevent interruptions due to 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. 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 forms the resistance. The liquid metal formed in either furnace 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 silical blocks or flower pots. Though crude, these simple furnaces can melt a wide range of materials, create calcium carbide, etc.

Cooling methods

Systems spray cooled spray bars
Non-pressurized cooling system

Smaller arc furnaces may be adequately cooled by circulation of air over structural elements of 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 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. However 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 the refractory in the hearth leading to a break out of molten metal or in the worst case a steam explosion.

Plasma arc furnace

A plasma arc furnace (PAF) uses plasma torches instead of graphite electrodes. Each of these torches consists of a casing provided with a nozzle and an axial tubing for feeding a plasma-forming gas (either nitrogen or argon), and a burnable cylindrical graphite electrode located within the tubing. Such furnaces can be referred to as "PAM" (Plasma Arc Melt) furnaces. They are used extensively in the titanium melt industry and similar specialty metals industries.[10]

Vacuum arc remelting

Vacuum arc remelting (VAR) is a secondary remelting process for vacuum refining and manufacturing of ingots with improved chemical and mechanical homogeneity.

In critical military and commercial aerospace applications, material engineers commonly specify VIM-VAR steels. VIM means Vacuum Induction Melted and VAR means Vacuum Arc Remelted. VIM-VAR steels become bearings for jet engines, rotor shafts for military helicopters, flap actuators for fighter jets, gears in jet or helicopter transmissions, mounts or fasteners for jet engines, jet tail hooks and other demanding applications.

Most grades of steel are melted once and are then cast or teemed into a solid form prior to extensive forging or rolling to a metallurgically sound form. In contrast, VIM-VAR steels go through two more highly purifying melts under vacuum. After melting in an electric arc furnace and alloying in an argon oxygen decarburization vessel, steels destined for vacuum remelting are cast into ingot molds. The solidified ingots then head for a vacuum induction melting furnace. This vacuum remelting process rids the steel of inclusions and unwanted gases while optimizing the chemical composition. The VIM operation returns these solid ingots to the molten state in the contaminant-free void of a vacuum. This tightly controlled melt often requires up to 24 hours. Still enveloped by the vacuum, the hot metal flows from the VIM furnace crucible into giant electrode molds. A typical electrode stands about 15 feet (5 m) tall and will be in various diameters. The electrodes solidify under vacuum.

For VIM-VAR steels, the surface of the cooled electrodes must be ground to remove surface irregularities and impurities before the next vacuum remelt. Then the ground electrode is placed in a VAR furnace. In a VAR furnace the steel gradually melts drop-by-drop in the vacuum-sealed chamber. Vacuum arc remelting further removes lingering inclusions to provide superior steel cleanliness and further remove gases such as oxygen, nitrogen and hydrogen. Controlling the rate at which these droplets form and solidify ensures a consistency of chemistry and microstructure throughout the entire VIM-VAR ingot. This in turn makes the steel more resistant to fracture or fatigue. This refinement process is essential to meet the performance characteristics of parts like a helicopter rotor shaft, a flap actuator on a military jet or a bearing in a jet engine.

For some commercial or military applications, steel alloys may go through only one vacuum remelt, namely the VAR. For example, steels for solid rocket cases, landing gears or torsion bars for fighting vehicles typically involve the one vacuum remelt.

Vacuum arc remelting is also used in production of titanium and other metals which are reactive or in which high purity is required.

See also

References

  1. ^ US patent 417943
  2. ^ THe History of Phosphorus, Arthur Toy
  3. ^ "::Crucible Industries:: Our History". www.crucibleservice.com.
  4. ^ "Home". worldsteel.org.
  5. ^ Preston, R., American Steel. Avon Books, New York, 1991
  6. ^ a b H. W. Beaty (ed.), Standard Handbook for Electrical Engineers, 11th Ed., McGraw Hill, New York 1978, ISBN 0-07-020974-X pages 21.171-21.176
  7. ^ Benoit Boulet, Gino Lalli and Mark Ajersch, Modeling and Control of an Electric Arc Furnace, accessed 2014-05-24
  8. ^ "Graphite Electrodes Solutions from GrafTech". graftech.com.
  9. ^ "Cross section of electric arc furnace". Kandi Engineering. Retrieved 16 April 2016.
  10. ^ "PLASMA ARC FURNACE". www.thermopedia.com.

Further reading

  • J.A.T. Jones, B. Bowman, P.A. Lefrank, "Electric Furnace Steelmaking", in The Making, Shaping and Treating of Steel, R.J. Fruehan, Editor. 1998, The AISE Steel Foundation: Pittsburgh. p. 525–660.
  • Thomas Commerford Martin and Stephen Leidy Coles, The Story of Electricity, New York 1919, no ISBN, Chapter 13 "The Electric Furnace", available on the Internet Archive

External links

CELSA Group

CELSA Group is one of the leading European multinationals in long steel products, the most diversified and vertically integrated. It currently operates in 11 countries and has six large business groups with steel mills, rolling mills, transformation plants, distribution, service centers and recycling. The company has an extensive and excellent commercial network worldwide to provide service to all its customers.

CELSA Group and the companies that operate under its brand represent the largest producer of long products in Spain and one of the main European producers. The company has industrial presence in Denmark, Spain, Finland, France, Norway, Poland, Sweden and the United Kingdom.

Chandrapur Ferro Alloy Plant

Chandrapur Ferro Alloy Plant, (CFP) erstwhile Maharashtra Elektrosmelt Ltd. (MEL) became a Unit of SAIL w.e.f. 12/7/2011. Chandrapur Ferro Alloy Plant is the only Public sector Unit engaged in production of Manganese based Ferro Alloys in the Country

The plant is situated amongst picturesque surroundings at Chandrapur (Maharashtra). It is located 166 km away from Nagpur on Delhi-Chennai rail route and is well connected by rail & road to the major cities of India.

CFP has an installed capacity of 1,00,000 TPY Ferro Manganese. The product range of CFP includes High Carbon Ferro Manganese, Silico Manganese and Medium/Low Carbon Ferro Manganese. The Plant is accredited with Quality Assurance Certificate ISO 9001:2008.CFP's major production facilities include two nos. of 33 MVA Submerged Electric Arc Furnaces for the production of Ferro alloys, two nos. Manganese Ore Sintering Plants, Furnace gas based Power Plant, Mechanized Crushing and Screening System for Ferro Alloys and 1 MVA Electric Arc Furnace for the production of Medium Carbon and Low Carbon Ferro Manganese with Lime Calcination and Manganese Ore Roasting Unit.

The plant is a leader in ferroalloy technology. Activities for technological developments are taken up in areas like raw material preparation, raw material substitution, furnace operation, ferroalloy casting and processing etc.

One example of the latest technological development is the state of the art ‘Layer Casting Technology’ for casting molten Ferro Alloys and Ferro Alloy Processing Unit (Crusher) which is the first of its kind in India.

Cyril Frank Elwell

Cyril Frank Elwell (August 20, 1884 – 1963) was an Australian-born American inventor and pioneer in development of radio.

Elwell arrived in the United States in 1902. He applied to Stanford University and entered the electrical engineering program there. In 1906, he organized fellow students to participate in repairs at the campus, owing to the San Francisco earthquake. He graduated in 1907. He founded the Poulsen Wireless Telephone and Telegraph Company, later renamed Federal Telegraph Company in 1909.Elwell designed a large transformer for electric arc furnace reduction of iron ore; this became the topic of his thesis. He had published some technical papers on applications in electric metallurgy. In 1908 he switched interests to wireless communication after investigating a system for voice transmission by spark gap transmitter invented by Francis Joseph McCarty (1888-1906) in 1902. After demonstrating the concept and obtaining financial backing for further research, McCarty had been killed in an automobile accident. His investors had contacted Harris J. Ryan at Standford, who referred them to Elwell. The apparatus Elwell had evaluated proved unsuitable, but he knew of the Poulsen arc converter, which differed from the spark gap in producing a continuous wave. This, Elwell knew, would be more suitable for wireless transmission of voice.

By 1910 Elwell had demonstrated voice communication between Stockton and Sacramento, California. Equipment and technique rapidly improved and by 1911 Federal Telegraph was prepared to bid on contracts to provide Navy communication to Hawaii. After a dispute with the board of directors, Elwell resigned from Federal Telegraph in 1913 but continued radio research, joining the short-lived Universal Wireless Syndicate. During World War I he was a consulting radio engineer for the French and Italian governments. Elwell was one of the founders of the Mullard company, manufacturers of vacuum tubes. After his term as director at Mullard, he returned to the United States in 1947 and was a consulting engineer for Hewlett Packard. He died in 1963.

Electron-beam furnace

An electron-beam furnace (EB furnace) is a type of vacuum furnace employing high-energy electron beam in vacuum as the means for delivery of heat to the material being melted. It is one of the electron-beam technologies.

Electron-beam furnaces are used for production and refining of high-purity metals (especially titanium, vanadium, tantalum, niobium, hafnium, etc.) and some exotic alloys. The EB furnaces use a hot cathode for production of electrons and high voltage for accelerating them towards the target to be melted.

An alternative for an electron-beam furnace can be an electric arc furnace in vacuum.Somewhat similar technologies are electron-beam melting and electron-beam welding.

Ferromanganese

Ferromanganese, a ferroalloy with high content of manganese, is made by heating a mixture of the oxides MnO2 and Fe2O3, with carbon, usually as coal and coke, in either a blast furnace or an electric arc furnace-type system, called a submerged arc furnace. The oxides undergo carbothermal reduction in the furnaces, producing the ferromanganese. Ferromanganese is used as a deoxidizer for steel.

Henry Bessemer invented the use of ferromanganese as a method of introducing manganese in controlled proportions during the production of steel. The advantage of combining powdered iron oxide and manganese oxide together is the lower melting point of the combined alloy compared to pure manganese oxide.

A North American standard specification is ASTM A99. The ten grades covered under this specification includes;

Standard ferromanganese

Medium-carbon ferromanganese

Low-carbon ferromanganeseA similar material is a pig iron with high content of manganese, is called spiegeleisen.

Flodin process

The Flodin process is a direct reduction process for manufacturing modern iron, developed by Gustaf Henning Flodin from Sweden and patented in 1924.

Using a specially constructed electric arc furnace, a mixture of hematite and coal is smelted in a continuous process, with the reduced metal accumulating at the bottom of the furnace, where it can be tapped off.

Furnace

A furnace is a device used for high-temperature heating. The name derives from Latin word fornax, which means oven. The heat energy to fuel a furnace may be supplied directly by fuel combustion, by electricity such as the electric arc furnace, or through induction heating in induction furnaces.

In American English and Canadian English usage, the term furnace refers to the household heating systems based upon a central furnace, otherwise known either as a boiler, or a heater in British English. Furnace may also be a synonym for kiln, a device used in the production of ceramics.

In British English, a furnace is an industrial furnace used for many things, such as the extraction of metal from ore (smelting) or in oil refineries and other chemical plants, for example as the heat source for fractional distillation columns. The term furnace can also refer to a direct fired heater, used in boiler applications in chemical industries or for providing heat to chemical reactions for processes like cracking, and is part of the standard English names for many metallurgical furnaces worldwide.

GrafTech

GrafTech International Ltd. is a manufacturer of graphite electrodes and petroleum coke, which are essential for the production of electric arc furnace steel and other metals. The company is headquartered in Brooklyn Heights, Ohio and has manufacturing facilities in Calais, France, Pamplona, Spain, Monterrey, Mexico, and St. Marys, Pennsylvania.

Kinsevere

Kinsevere is an open pit mine and Heavy Media Separation plant with an electric arc furnace formerly operated by Anvil Mining, and now operated by Minerals and Metals Group.

It is located 30 kilometres (19 mi) north of Lubumbashi, Katanga Province, Democratic Republic of Congo.Kinsevere is in the Kipushi Territory in Katanga province.

There are three deposits: Central Pit, Mashi and Kinsevere Hill.

These are mostly stratiform deposits in alternating dolomitic and terrigenous formations.

The dolomitic rocks that underlay the formations are excellent aquifers.For the year of 2011, Anvil expected to produce between 36,000 and 38,000 tonnes of copper as copper cathodes and copper in concentrates. Anvil was completing construction of a $400 million SX-EW plant to extract the copper, and the Heavy Media Separation plant was scheduled to shut down at the end of June 2011.

After the upgrades, the mine is expected to produce about 60,000 tons of copper annually. Anvil is studying the potential for further increasing the rate of production.

In 2012 Minerals and Metals Group made a successful takeover bid for Anvil worth $1.3 billion.

Nickel pig iron

Nickel pig iron (NPI) is a low grade ferronickel invented in China as a cheaper alternative to pure nickel for the production of stainless steel. The production process of nickel pig iron utilizes laterite nickel ores instead of pure nickel sold on the world market. The alternative was developed as a response to high price of pure nickel. The estimated cost of a ton of nickel pig iron ranged between US$16,500 and $18,000 in 2012, and this cheaper substitute for pure nickel influences the price of nickel on the world market by lowering the demand in certain applications, the most important being the production of stainless steel, representing about two thirds of nickel use.

Nickel pig iron is made of low-grade nickel ore, coking coal, and a mixture of gravel and sand as an aggregate. This mixture is heated in either a blast furnace or an electric arc furnace depending on the desired grade. Impurities are then removed via smelting and sintering processes and the resulting nickel pig iron contains four to 13 percent pure nickel. According to Canadian Sudbury nickel pig iron equals "dirty nickel", because the production process is not environmentally friendly, the carbon dioxide emissions being particularly high. China had imported most of the nickel containing ore from Indonesia and the Philippines, but as of Jan 2014 Indonesia has banned the export of ore. China imported 53 percent of the nickel ore from Indonesia in 2011.

While China is credited with the invention of NPI there are reports that NPI has been around for more than 100 years but it was the Chinese who successfully made the production commercially viable.

Open hearth furnace

Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel. Since steel is difficult to manufacture due to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was developed to overcome this difficulty. Compared to Bessemer steel, which it displaced, its main advantages were that it did not expose the steel to excessive nitrogen (which would cause the steel to become brittle), was easier to control, and it permitted the melting and refining of large amounts of scrap iron and steel.

The open hearth furnace was first developed by German-born engineer Carl Wilhelm Siemens. In 1865, the French engineer Pierre-Émile Martin took out a license from Siemens and first applied his regenerative furnace for making steel. Their process was known as the Siemens–Martin process, and the furnace as an "open-hearth" furnace. Most open hearth furnaces were closed by the early 1990s, not least because of their slow operation, being replaced by the basic oxygen furnace or electric arc furnace.

Whereas earliest witness of open hearth steelmaking about 2000 years ago was found in the culture of the Haya people in present day Tanzania, and in Europe in the Catalan forge, invented in Spain in the 8th century, it is usual to confine the term to certain 19th-century and later steelmaking processes, thus excluding bloomeries (including the Catalan forge), finery forges, and puddling furnaces from its application.

Paul Héroult

Paul (Louis-Toussaint) Héroult (10 April 1863 – 9 May 1914) was a French scientist. He was the inventor of the aluminium electrolysis and developed the first successful commercial electric arc furnace. He lived in Thury-Harcourt, Normandy.

SAE steel grades

The SAE steel grades system is a standard alloy numbering systems for steel grades maintained by SAE International.

In the 1930s and 1940s the American Iron and Steel Institute (AISI) and SAE were both involved in efforts to standardize such a numbering system for steels. These efforts were similar and overlapped significantly. For several decades the systems were united into a joint system designated the AISI/SAE steel grades. In 1995 the AISI turned over future maintenance of the system to SAE because the AISI never wrote any of the specifications.Today steel quotes and certifications commonly make reference to both SAE and AISI, not always with precise differentiation. For example, in the alloy/grade field, a cert might say "4140", "AISI 4140", or "SAE 4140", and in most light-industrial applications any of the above is accepted as adequate, and considered equivalent, for the job at hand, as long as the specific specification called out by the designer (for example, "4140 bar per ASTM-A108" or "4140 bar per AMS 6349") is certified to on the certificate. The alloy number is simply a general classifier, whereas it is the specification itself that narrows down the steel to a very specific standard.

The SAE steel grade system's correspondence to other alloy numbering systems, such as the ASTM-SAE unified numbering system (UNS), can be seen in cross-referencing tables (including the ones given below).

The AISI system uses a letter prefix to denote the steelmaking process. The prefix "C" denotes open-hearth furnace, electric arc furnace or basic oxygen furnace, while "E" denotes electric arc furnace steel. A letter "L" within the grade name indicates lead as an added ingredient; for example, 12L14 is a common grade that is 1214 with lead added for machinability.

Sheerness Steelworks

Sheerness Steelworks was a steel plant located at Sheerness, on the Isle of Sheppey, in Kent, England. The plant opened in 1971 and produced steel via the Electric Arc Furnace (EAF) method rather than as a primary metal by the smelting of iron ore. The plant has closed down twice in its history; first in 2002 and again in 2012. Current owners Liberty House, had announced plans to re-open part of the site in 2016.

Stassano furnace

The Stassano furnace is an electric arc furnace for the production of steel. Invented by Ernesto Stassano in 1898, it is the first electric furnace in history for ferrous metallurgy.

Steel mill

A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also describe plants where steel semi-finished casting products (blooms, ingots, slabs, billets) are made, from molten pig iron or from scrap.

Steelmaking

Steelmaking is the process for producing steel from iron ore and scrap. In steelmaking, impurities such as nitrogen, silicon, phosphorus, sulfur and excess carbon are removed from the sourced iron, and alloying elements such as manganese, nickel, chromium and vanadium are added to produce different grades of steel. Limiting dissolved gases such as nitrogen and oxygen, and entrained impurities (termed "inclusions") in the steel is also important to ensure the quality of the products cast from the liquid steel.Steelmaking has existed for millennia, but it was not commercialized on a massive scale until the 19th century. The ancient craft process of steelmaking was the crucible process. In the 1850s and 1860s, the Bessemer process and the Siemens-Martin process turned steelmaking into a heavy industry. Today there are two major commercial processes for making steel, namely basic oxygen steelmaking, which has liquid pig-iron from the blast furnace and scrap steel as the main feed materials, and electric arc furnace (EAF) steelmaking, which uses scrap steel or direct reduced iron (DRI) as the main feed materials. Oxygen steelmaking is fuelled predominantly by the exothermic nature of the reactions inside the vessel; in contrast, in EAF steelmaking, electrical energy is used to melt the solid scrap and/or DRI materials. In recent times, EAF steelmaking technology has evolved closer to oxygen steelmaking as more chemical energy is introduced into the process.

Submerged-arc furnace for phosphorus production

The Submerged-arc furnace for phosphorus production is a particular sub-type of electric arc furnace used to produce phosphorus and other products. Submerged arc furnaces are mainly used for the production of ferroalloys. The nomenclature submerged means that the furnace's electrodes are buried deep in the furnace burden. A reduction reaction takes place near the tip of the electrodes to facilitate the furnace's process.

Iron and steel production
Iron production
(Ironworks)
Steelmaking
(Steel mill)
Production by country
Heat treatment methods

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.