Slag

Slag is the glass-like by-product left over after a desired metal has been separated (i.e., smelted) from its raw ore. Slag is usually a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and elemental metals. While slags are generally used to remove waste in metal smelting, they can also serve other purposes, such as assisting in the temperature control of the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal.

Slag2
A path through a slag heap in Clarkdale, Arizona, showing the striations from the rusting corrugated sheets retaining it.
The Manufacture of Iron -- Carting Away the Scoriae
The Manufacture of Iron – Carting Away the Scoriæ (slag), an 1873 wood engraving

Ore smelting

In nature, iron, copper, lead, nickel and other metals are found in impure states called ores, often oxidized and mixed in with silicates of other metals. During smelting, when the ore is exposed to high temperatures, these impurities are separated from the molten metal and can be removed. Slag is the collection of compounds that are removed. In many smelting processes, oxides are introduced to control the slag chemistry, assisting in the removal of impurities and protecting the furnace refractory lining from excessive wear. In this case, the slag is termed synthetic. A good example is steelmaking slag: quicklime and magnesite are introduced for refractory protection, neutralising the alumina and silica separated from the metal, and assist in the removal of sulfur and phosphorus from the steel.

Slag runoff Republic Steel
Slag run-off from one of the open hearth furnaces of a steel mill, Republic Steel, Youngstown, Ohio, November 1941. Slag is drawn off the furnace just before the molten steel is poured into ladles for ingotting.

Ferrous and non-ferrous smelting processes produce different slags. The smelting of copper, lead and bauxite in non-ferrous smelting, for instance, is designed to remove the iron and silica that often occurs with those ores, and separates them as iron-silicate-based slags. Slag from steel mills in ferrous smelting, on the other hand, is designed to minimize iron loss and so mainly contains oxides of calcium, silicon, magnesium, and aluminium. Any sandy component or quartz component of the original ore automatically carries through the smelting process as silicon dioxide.

As the slag is channeled out of the furnace, water is poured over it. This rapid cooling, often from a temperature of around 2,600 °F (1,430 °C), is the start of the granulating process. This process causes several chemical reactions to take place within the slag, and gives the material its cementitious properties.

The water carries the slag in its slurry format to a large agitation tank, from where it is pumped along a piping system into a number of gravel based filter beds. The filter beds then retain the slag granules, while the water drains away and is returned to the system.

When the filtering process is complete, the remaining slag granules, which now give the appearance of coarse beach sand, can be scooped out of the filter bed and transferred to the grinding facility where they are ground into particles that are finer than Portland cement.

Ancient uses

Slag from iron ore melting
Early slag from Denmark, c. 200-500 CE

During the Bronze Age of the Mediterranean there were a vast number of differential metallurgical processes in use. A slag by-product of such workings was a colorful, glassy, vitreous material found on the surfaces of slag from ancient copper foundries. It was primarily blue or green and was formerly chipped away and melted down to make glassware products and jewelry. It was also ground into powder to add to glazes for use in ceramics. Some of the earliest such uses for the by-products of slag have been found in ancient Egypt.[1]

Historically, the re-smelting of iron ore slag was common practice, as improved smelting techniques permitted greater iron yields—in some cases exceeding that which was originally achieved. During the early 20th century, iron ore slag was also ground to a powder and used to make agate glass, also known as slag glass.[2]

Modern uses

Ground granulated slag is often used in concrete in combination with Portland cement as part of a blended cement. Ground granulated slag reacts with water to produce cementitious properties. Concrete containing ground granulated slag develops strength over a longer period, leading to reduced permeability and better durability. Since the unit volume of Portland cement is reduced, this concrete is less vulnerable to alkali-silica and sulfate attack.

This previously unwanted recycled product is used in the manufacture of high-performance concretes, especially those used in the construction of bridges and coastal features, where its low permeability and greater resistance to chlorides and sulfates can help to reduce corrosive action and deterioration of the structure.[3] The slag can also be used to create fibers used as an insulation material called slag wool.

Basic slag

Basic slag is a co-product of steelmaking, and is typically produced either through the blast furnace - oxygen converter route or the electric arc furnace - ladle furnace route.[4] To flux the silica produced during steelmaking, limestone and/or dolomite are added, as well as other types of slag conditioners such as calcium aluminate or fluorspar. The major components of these slags therefore include the oxides of calcium, magnesium, silicon, iron, and aluminum, with lesser amounts of manganese, phosphorus, and others depending on the specifics of the raw materials used.

Because of the slowly released phosphate content in phosphorus-containing slag, and because of its liming effect, it is valued as fertilizer in gardens and farms in steel making areas. However, the most important application is construction.[5]

See also

References

  1. ^ "The chemical composition of glass in Ancient Egypt by Mikey Brass (1999)". Retrieved 2009-06-18.
  2. ^ "Glass (G) – Encyclopedia of Antiques". Encyclopedia of Antiques. Retrieved 5 April 2014.
  3. ^ "High Performance Cement for High Strength and Extreme Durability by Konstantin Sobolev". Archived from the original on 2009-08-03. Retrieved 2009-06-18.
  4. ^ Fruehan, Richard (1998). The Making, Shaping, and Treating of Steel, Steelmaking and Refining Volume, 11th Edition. Pittsburgh, PA, USA: The AISE Steel Foundation. p. 10. ISBN 0-930767-02-0.
  5. ^ fehs.de

Further reading

  • Dimitrova, S.V. (1996). "Metal sorption on blast-furnace slag". Water Research. 30 (1): 228–232. doi:10.1016/0043-1354(95)00104-S.
  • Roy, D.M. (1982). "Hydration, structure, and properties of blast furnace slag cements, mortars, and concrete". ACI Journal Proceedings. 79 (6).
  • Fredericci, C.; Zanotto, E.D.; Ziemath, E.C. (2000). "Crystallization mechanism and properties of a blast furnace slag glass". Journal of Non-Crystalline Solids. 273 (1–3): 64–75. Bibcode:2000JNCS..273...64F. doi:10.1016/S0022-3093(00)00145-9.
Bloomery

A bloomery is a type of furnace once used widely for smelting iron from its oxides. The bloomery was the earliest form of smelter capable of smelting iron. A bloomery's product is a porous mass of iron and slag called a bloom. This mix of slag and iron in the bloom is termed sponge iron, which is usually consolidated and further forged into wrought iron. The bloomery has now largely been superseded by the blast furnace, which produces pig iron.

Construction aggregate

Construction aggregate, or simply "aggregate", is a broad category of coarse to medium grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt concrete; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties (e.g. to help prevent differential settling under the road or building), or as a low-cost extender that binds with more expensive cement or asphalt to form concrete.

Preferred bituminous aggregate sizes for road construction are given in EN 13043 as d/D (where the range shows the smallest and largest square mesh grating that the particles can pass). The same classification sizing is used for larger armour stone sizes in EN 13383, EN 12620 for concrete aggregate, EN 13242 for base layers of road construction and EN 13450 for railway ballast.

The American Society for Testing and Materials publishes an exhaustive listing of specifications including ASTM D 692 and ASTM D 1073 for various construction aggregate products, which, by their individual design, are suitable for specific construction purposes. These products include specific types of coarse and fine aggregate designed for such uses as additives to asphalt and concrete mixes, as well as other construction uses. State transportation departments further refine aggregate material specifications in order to tailor aggregate use to the needs and available supply in their particular locations.

Sources for these basic materials can be grouped into three main areas: Mining of mineral aggregate deposits, including sand, gravel, and stone; use of waste slag from the manufacture of iron and steel; and recycling of concrete, which is itself chiefly manufactured from mineral aggregates. In addition, there are some (minor) materials that are used as specialty lightweight aggregates: clay, pumice, perlite, and vermiculite.

Copper extraction

Copper extraction refers to the methods used to obtaining copper from its ores. The conversion of copper consists of a series of physical and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.

As in all mining operations, the ore must usually be beneficiated (concentrated). The processing techniques depend on the nature of the ore. If the ore is primarily sulfide copper minerals (such as chalcopyrite), the ore is crushed and ground to liberate the valuable minerals from the waste ('gangue') minerals. It is then concentrated using mineral flotation. The concentrate is typically then sold to distant smelters, although some large mines have smelters located nearby. Such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The sulfide concentrates are typically smelted in such furnaces as the Outokumpo or Inco flash furnace or the ISASMELT furnace to produce matte, which must be converted and refined to produce anode copper. Finally, the final refining process is electrolysis. For economic and environmental reasons, many of the byproducts of extraction are reclaimed. Sulfur dioxide gas, for example, is captured and turned into sulfuric acid — which can then be used in the extraction process or sold for such purposes as fertiliser manufacture.

Oxidised copper ores can be treated by hydrometallurgical extraction.

Dinobots

Dinobots are a type of character in the fictional Transformers Universe. The Dinobots group consists of several subgroups of robots, each of whose transformed mode is that of a dinosaur or similar prehistoric animal. Dinobots are referred to as Dinotrons in the Japanese version, and Dinobots (ダイノボット, Dainobotto) in the Japanese dub of Transformers Animated. They were named among the top selling toys in 1985 by Playthings magazine.

Dross

Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low-melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal. For higher melting point metals such as steel, oxidized impurities melt and float making them easy to pour off.

With wrought iron, hammering and later rolling removed some dross.

With tin and lead the dross can be removed by adding sodium hydroxide pellets, which dissolve the oxides and form a slag. If floating, dross can also be skimmed off.

Dross, as a solid, is distinguished from slag, which is a liquid. Dross product is not entirely waste material; for example, aluminium dross can be recycled and is used in secondary steelmaking for slag deoxidation.

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.

Electro-slag remelting

Electroslag remelting (ESR), also known as electro-flux remelting, is a process of remelting and refining steel and other alloys for mission-critical applications in aircraft, thermal power stations, nuclear power plants, military technology, et al.The electroslag remelting (ESR) process is used to remelt and refine steels and various super-alloys, resulting in high-quality ingots. This process can be started up through vacuum induction melting. The ESR process uses the as-cast alloy as a consumable electrode. Electric current (generally AC) is passed between the electrode and the new ingot, which is formed in the bottom of a water-cooled copper mold. The new ingot is covered in an engineered slag that is superheated by the electric current. The electrode tip is slowly melted from contact with the slag. These metal droplets travel through the slag to the bottom of the water-cooled mold and slowly freeze as the ingot is directionally solidified upwards from the bottom of the mold. The slag pool floats above the refined alloy, continuously floating upwards as the alloy solidifies. The molten metal is cleaned of impurities that chemically react with the slag or otherwise float to the top of the molten pool as the molten droplets pass through the slag.Electroslag remelting uses highly reactive slags (calcium fluoride, lime, alumina, or other oxides are usually the main components) to reduce the amount of type-A sulfide present in biometal alloys. It is a common practice in European industries. ESR reduces other types of inclusions as well, and is seen as an alternative to the vacuum arc remelting method that is prevalent in US industries.

An example of the use of the electro-slag refined (ESR) steel technique is the L30 tank gun.

Ground granulated blast-furnace slag

Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder.

Hickey

A hickey, hickie or love bite in British English, is a bruise or bruise-like mark caused by the kissing or sucking of the skin, usually on the neck or arm. While biting might be part of giving a hickey, sucking is sufficient to burst small superficial blood vessels under the skin.

The origin of the word is from its earlier meaning of "pimple, skin lesion" (c. 1915); perhaps a sense extension and spelling variation from the earlier word meaning "small gadget, device; any unspecified object" which has an unknown origin (1909).Hickeys typically last from 5 to 12 days and may be treated in the same way as other bruises. Ways to reduce the appearance of hickeys include icing recent hickeys to reduce swelling, rubbing them with a chilled spoon to remove the bruise, and applying a warm compress to older hickeys to dilate vessels and promote blood flow. They can be covered with a concealer or powder corresponding to the sufferer's skin tone, or a fake tan. Alternatively, articles of clothing such as scarves, snoods, turtle necks, or sleeves may be used to conceal hickeys.

Lapilli

Lapilli is a size classification term for tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. Lapilli (singular: lapillus) is Latin for "little stones".

By definition lapilli range from 2 to 64 mm (0.08 to 2.52 in) in diameter. A pyroclastic particle greater than 64 mm in diameter is known as a volcanic bomb when molten, or a volcanic block when solid. Pyroclastic material with particles less than 2 mm in diameter is referred to as volcanic ash.

Mike Paradinas

Michael Paradinas (born 26 September 1971), better known by his stage name μ-Ziq (pronounced "music" or mu-zik), is an English electronic musician from Wimbledon, London. He was associated with the electronic style intelligent dance music (IDM) during the 1990s, and recorded on Rephlex Records alongside artists such as Aphex Twin and Squarepusher. His critically acclaimed 1997 album, Lunatic Harness, helped defined the drill 'n' bass subgenre and was also his most successful release, selling over 100,000 copies. He is also founder of the record label Planet Mu, begun in 1995, where he has championed genres such as juke and footwork.

Mineral wool

Mineral wool is any fibrous material formed by spinning or drawing molten mineral or rock materials such as slag and ceramics.Applications of mineral wool include thermal insulation (as both structural insulation and pipe insulation, though it is not as fire-resistant as high-temperature insulation wool), filtration, soundproofing, and hydroponic growth medium.

Slut

Slut is generally a term for a woman or girl who is considered to have loose sexual morals or who is sexually promiscuous. It is usually used as an insult, sexual slur or offensive term of disparagement (slut-shaming). It originally meant "a dirty, slovenly woman", and is rarely used to refer to men, generally requiring clarification by use of the terms male slut or man whore.The first recorded use of the word was a reference to a man, in Geoffrey Chaucer's The Canterbury Tales, in which he is referring to the man's untidy appearance.

Slut-shaming is a related term, referring to the act of drawing attention to a person's promiscuous behavior for the purpose of shaming them socially. From the late 20th century, there have been attempts to reclaim the word, exemplified by various SlutWalk parades, and some individuals embrace the title as a source of pride.

Smelting

Smelting is a process of applying heat to ore in order to extract out a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind. The reducing agent is commonly a source of carbon, such as coke—or, in earlier times, charcoal.The carbon (or carbon monoxide derived from it) removes oxygen from the ore, leaving the elemental metal. The carbon thus oxidizes in two stages, producing first carbon monoxide and then carbon dioxide. As most ores are impure, it is often necessary to use flux, such as limestone, to remove the accompanying rock gangue as slag.

Plants for the electrolytic reduction of aluminium are also generally referred to as aluminium smelters.

Labourers working in the smelting industry have reported respiratory illnesses inhibiting their ability to perform the physical tasks demanded by their jobs.

South Deering, Chicago

South Deering, located on Chicago's far South Side, is the largest of the 77 official community areas of that city. It is part of the 10th Ward, once under the control of former Richard J. Daley ally Alderman Edward Vrdolyak. Primarily an industrial neighborhood, a small group of homes exists in the northeast corner and Lake Calumet takes up a large portion of the area. 80% of the community is zoned as industrial, natural wetlands, or parks. The remaining 20% is zoned for residential and small-scale commercial uses. The neighborhood is named for Charles Deering, an executive in the Deering Harvester Company that would later form a major part of International Harvester. International Harvester owned Wisconsin Steel, which was originally established in 1875 and was located along Torrence Avenue south of 106th Street to 109th Street. It is the location of Calumet Fisheries, a historic seafood restaurant that opened in 1928 and has been featured on Anthony Bourdain: No Reservations. The original Calumet Bakery store, a South Side favorite since 1935, is located at 2510 E 106th St, Chicago, IL 60617. It was also the location of the Wisconsin Steel Works, originally the Joseph H. Brown Iron and Steel Company, which opened in 1875 and closed in 1980. Since the closing of the steel mill, the neighborhood has remained economically depressed.

Louis Rosen documented the racial transition of this and nearby communities in his 1998 book The South Side: The Racial Transformation of an American Neighborhood.

Spoil tip

A spoil tip (also called a spoil bank, boney pile, gob pile, bing, batch, boney dump or pit heap) is a pile built of accumulated spoil – the overburden or other waste rock removed during coal and ore mining. These waste materials are typically composed of shale, as well as smaller quantities of carboniferous sandstone and various other residues. Spoil tips are not formed of slag, but in some areas they are referred to as slag heaps.

The term "spoil" is also used to refer to material removed when digging a foundation, tunnel, or other large excavation. Such material may be ordinary soil and rocks, or may be heavily contaminated with chemical waste, determining how it may be disposed of. Clean spoil may be used for land reclamation.

Spoil is distinct from tailings, which is the processed material that remains after the valuable components have been extracted from ore.

Ugg boots

Ugg boots are a unisex style of sheepskin boot originating in Australia and New Zealand. The boots are typically made of twin-faced sheepskin with fleece on the inside, a tanned outer surface and a synthetic sole. The term, ugg boots, originated from Australia, initially for utilitarian footwear worn for warmth, and which were often worn by surfers during the 1960s. In the 1970s, the boots were introduced to the surf culture of the United Kingdom and the United States. Sheepskin boots became a fashion trend in the U.S. in the late 1990s and as a worldwide trend in the mid-2000s. In Australia, they are worn predominantly as slippers and often associated with "daggy" fashion sense and "bogan" culture.Prior legal disputes between some manufacturers of sheepskin boots arose as to distinguish whether "ugg" is a protected trademark, or a generic term and thus ineligible for trademark protection. There are more than 70 registered trademarks that include the term "ugg" in various logos and designs in Australia and New Zealand, as the term is considered a generic reference to a type of shoe. Outside Australia and New Zealand, UGG is a brand manufactured by the California-based Deckers Outdoor Corporation, with most of its manufacturing based in China and with registered trademarks in over 130 countries worldwide including the US, UK, Canada, all European Union members, and China.A noteworthy manufacturer in Australia and New Zealand is the Luda Productions of Australia, which has roughly 75% of the market share in Australia; EMU Australia; Euram Ugg; Blue Mountains Ugg Boots; Original UGG Boots; Mortels Sheepskin Factory; Bearpaw; Uggs-N-Rugs; Binder Corporation and Westhaven Industries. Deckers is the leading manufacturer of the footwear style outside Australia. By 2010, worldwide sales by Australian manufacturers combined equaled 5.9% of Deckers UGG boots sales, with UGG dominating the world market.

Wacky Races (1968 TV series)

Wacky Races is an American animated television series produced by Hanna-Barbera Productions. The series features 11 different cars racing against each other in various road rallies throughout America, with each driver hoping to win the title of the "World's Wackiest Racer".

The cartoon had a large number of regular characters, with 23 people and animals spread among the 11 race cars. Wacky Races ran on CBS from September 14, 1968, to January 4, 1969, and in syndication from 1976 to 1982. Seventeen episodes were produced, with each episode featuring two different races.

Wrought iron

Wrought iron is an iron alloy with a very low carbon (less than 0.08%) content in contrast to cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag inclusions (up to 2% by weight), which gives it a "grain" resembling wood that is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile, corrosion-resistant and easily welded. Before the development of effective methods of steelmaking and the availability of large quantities of steel, wrought iron was the most common form of malleable iron. It was given the name wrought because it was hammered, rolled or otherwise worked while hot enough to expel molten slag. The modern functional equivalent of wrought iron is mild or low carbon steel. Neither wrought iron nor mild steel contain enough carbon to be hardenable by heating and quenching.It is a highly refined iron with a small amount of slag forged out into fibres. The chemical analysis of the metal shows as much as 99 percent of iron. The slag characteristic of wrought iron is useful in blacksmithing operations and gives the material its peculiar fibrous structure. The non-corrosive slag constituent causes wrought iron to be resistant to progressive corrosion. Moreover, the presence of slag produces a structure which diminishes the effect of fatigue caused by shocks and vibrations.Historically, a modest amount of wrought iron was refined into steel, which was used mainly to produce swords, cutlery, chisels, axes and other edged tools as well as springs and files. The demand for wrought iron reached its peak in the 1860s, being in high demand for ironclad warships and railway use. However, as properties such as brittleness of mild steel improved with better ferrous metallurgy and as steel became less costly to make thanks to the Bessemer process and the Siemens-Martin process, the use of wrought iron declined.

Many items, before they came to be made of mild steel, were produced from wrought iron, including rivets, nails, wire, chains, rails, railway couplings, water and steam pipes, nuts, bolts, horseshoes, handrails, wagon tires, straps for timber roof trusses, and ornamental ironwork, among many other things.Wrought iron is no longer produced on a commercial scale. Many products described as wrought iron, such as guard rails, garden furniture and gates, are actually made of mild steel. They retain that description because they are made to resemble objects which in the past were wrought (worked) by hand by a blacksmith (although many decorative iron objects, including fences and gates, were often cast rather than wrought).

Mineral processing
(by physical means)
Pyrometallurgy
(by heat)
Hydrometallurgy
(by aqueous solution)
Electrometallurgy
(by electricity)
Co-products

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