steel

steel, alloy of iron, carbon, and small proportions of other elements. Iron contains impurities in the form of silicon, phosphorus, sulfur, and manganese; steelmaking involves the removal of these impurities, known as slag, and the addition of desirable alloying elements.

Production

Steel was first made by cementation, a process of heating bars of iron with charcoal in a closed furnace so that the surface of the iron acquired a high carbon content. The crucible method, originally developed to remove the slag from cementation steel, melts iron and other substances together in a fire-clay and graphite crucible. The famous blades of Damascus and of Toledo, Spain, were made by the cementation and crucible techniques.

The Bessemer process, the open-hearth process, and the basic oxygen process are more widely used in modern steelmaking. The open-hearth uses a type of furnace called a regenerative furnace; instead of a firebox at one end and a flue at the other, it has devices at each end for the intake and outflow of both fuel and air. The air is preheated by a system of current reversals that causes very high temperatures. This process, developed c.1866 by Sir William Siemens, uses iron ore and pig iron. In the basic oxygen process, or Linz-Donawitz process, developed in the 1950s, the design of the furnace is changed, and oxygen added to the air intake permits more rapid refining of the charge (material in the furnace). The electric-arc furnace is another modern development; it provides a means of making large quantities of high-grade steel, with the advantages of positive temperature control, freedom from contamination of the product by the fuel, and simultaneous deoxidation and desulfurization actions.

Steel is shaped for commercial use in rolling mills, where successive passages of the red-hot ingot between variously shaped rollers give it the desired form. Pittsburgh, one of the world's great steel centers, built its first rolling mill in 1811; Bessemer steel rails were rolled in Chicago as early as 1865.

Types and Uses

Steel is often classified by its carbon content: a high-carbon steel is serviceable for dies and cutting tools because of its great hardness and brittleness; low- or medium-carbon steel is used for sheeting and structural forms because of its amenability to welding and tooling. Alloy steels, now most widely used, contain one or more other elements to give them specific qualities. Aluminum steel is smooth and has a high tensile strength. Chromium steel finds wide use in automobile and airplane parts on account of its hardness, strength, and elasticity, as does the chromium-vanadium variety. Nickel steel is the most widely used of the alloys; it is nonmagnetic and has the tensile properties of high-carbon steel without the brittleness. Nickel-chromium steel possesses a shock resistant quality that makes it suitable for armor plate. Wolfram (tungsten), molybdenum, and high-manganese steel are other alloys. Stainless steel, which was developed in England, has a high tensile strength and resists abrasion and corrosion because of its high chromium content.

Tuned gong made from the end, and part of the wall, of an oil barrel. The barrel's end surface is hammered into a concave shape, and several areas are outlined by chiseled grooves. It is heated and tempered, and bosses or domes are hammered into the outlined areas; the depth, curvature, and size of each boss determines its pitch. Melodies, complex accompaniments, and counterpoint can be played with rubber-tipped mallets on a single drum. The steel drum originated in Trinidad in the 1940s. It is usually played in ensembles, called steel bands, of widely varying sizes.

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Alloy of iron and about 2percnt or less carbon. Pure iron is soft, but carbon greatly hardens it. Several iron-carbon constituents with different compositions and/or crystal structures exist: austenite, ferrite, pearlite, cementite, and martensite can coexist in complex mixtures and combinations, depending on temperature and carbon content. Each microstructure differs in hardness, strength, toughness, corrosion resistance, and electrical resistivity, so adjusting the carbon content changes the properties. Heat treating, mechanical working at cold or hot temperatures, or addition of alloying elements may also give superior properties. The three major classes are carbon steels, low-alloy steels, and high-alloy steels. Low-alloy steels (with up to 8percnt alloying elements) are exceptionally strong and are used for machine parts, aircraft landing gear, shafts, hand tools, and gears, and in buildings and bridges. High-alloy steels, with more than 8percnt alloying elements (e.g., stainless steels) offer unusual properties. Making steel involves melting, purifying (refining), and alloying, carried out at about 2,900°F (1,600°C). Steel is obtained by refining iron (from a blast furnace) or scrap steel by the basic oxygen process, the open-hearth process, or in an electric furnace, then by removing excess carbon and impurities and adding alloying elements. Molten steel can be poured into molds and solidified into ingots; these are reheated and rolled into semifinished shapes which are worked into finished products. Some steps in ingot pouring can be saved by continuous casting. Forming semifinished steel into finished shapes may be done by two major methods: hot-working consists primarily of hammering and pressing (together called forging), extrusion, and rolling the steel under high heat; cold-working, which includes rolling, extrusion, and drawing (see wire drawing), is generally used to make bars, wire, tubes, sheets, and strips. Molten steel can also be cast directly into products. Certain products, particularly of sheet steel, are protected from corrosion by electroplating, galvanizing, or tinplating.

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Any of a family of alloy steels usually containing 10–30percnt chromium. The presence of chromium, together with low carbon content, gives remarkable resistance to corrosion and heat. Other elements, such as nickel, molybdenum, titanium, aluminum, niobium, copper, nitrogen, sulfur, phosphorus, and selenium, may be added to increase corrosion resistance to specific environments, enhance resistance to oxidation (see oxidation-reduction), and impart special characteristics.

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Alloy of iron and carbon in which the carbon content may range from less than 0.015percnt to slightly more than 2percnt. Adding this tiny amount of carbon produces a material that exhibits great strength, hardness, and other valuable mechanical properties. Carbon steels account for about 90percnt of the world's steel production. They are used extensively for automobile bodies, appliances, machinery, ships, containers, and the structures of buildings. Carbon steel, formerly made by the Bessemer, crucible, or open-hearth process, is now made by the basic oxygen process, or by an arc furnace.

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Administrative agency designed to integrate the coal and steel industries of France, West Germany, Italy, Belgium, the Netherlands, and Luxembourg. It originated in the plan of Robert Schuman (1950) to establish a common market for coal and steel by those countries willing to submit to an independent authority. Created in 1952, the ECSC came to include all members of the European Union. It initially removed barriers to trade in coal, coke, steel, pig iron, and scrap iron; it later supervised the reduction of its members' excess production. In 1967 its governing bodies were merged into the European Community. When the treaty expired in 2002, the ECSC was dissolved.

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A steel-string acoustic guitar, is a modern form of guitar descended from the classical guitar, but strung with steel strings for a brighter, louder sound. Strictly speaking, the terms steel-stringed guitar, classical guitar, and folk guitar all refer to acoustic (that is, non-electric) guitars, though some of these terms refer to different types of instruments (nylon-strung vs. steel-strung). The term "acoustic guitar" is a retronym, since before the invention of the electric instrument, all guitars were "acoustic."

The standard tuning for an acoustic guitar is E-A-D-G-B-E (low to high), although many players, particularly fingerpickers, use alternate tunings (scordatura), such as "open G" (D-G-D-G-B-D), "open D tuning" (D-A-D-F-A-D), or "drop D" (D-A-D-G-B-E). A common mnemonic for standard tuning is "Eddie ate dynamite; good-bye Eddie",or "Every animal deserves good breakfast everyday", which aids beginners in remembering the string tuning sequence from low to high.

One variation on the standard acoustic guitar is the 12-string guitar, which sports an additional doubling string for each of the traditional six strings. This guitar was made famous by artists such as Lead Belly, Pete Seeger, and Leo Kottke.

Construction

There are many different variations on the construction of, and materials used in, steel-string guitars. More expensive guitars feature solid tonewood tops (sometimes spruce), sides and backs (often rosewood, maple, or mahogany). Lower-priced guitars typically combine solid tops with laminated (layers of wood) backs and sides. Entry-level guitars are usually made entirely of laminated wood. Necks are generally made of mahogany (either Philippine or Honduran) and fretboards are usually made of dense, tropical hardwoods such as rosewood or ebony. The various combinations of the different woods and their quality, along with design and construction elements (for example, how the top is braced), are among the factors affecting the timbre or "tone" of the guitar. Many players and builders feel a well-made guitar's tone improves over time.

Different body shapes acoustic guitars are commonly constructed in include the Dreadnought body style, an example of which would be the Martin HD-28, this is one of the most common styles, The Jumbo body style, an example of which would be the Gibson J-200, and the Grand Auditorium style, an example of which would be the Taylor Guitars GA7.

Typically, a steel-string acoustic guitar is built with a larger soundbox than a standard classical guitar. Because such instruments must withstand higher string tension than nylon-strung guitars, heavier construction is required overall. Steel-string guitars use different bracing systems from classical guitars, typically using X-bracing instead of the fan bracing used on classical and flamenco guitars. (Another simpler system, called ladder bracing, where the braces are all placed across the width of the instrument, is used on all types of flat-top guitars on the back.) Innovations in bracing design have emerged, most notably the A-brace developed by British luthier Roger Bucknall of Fylde Guitars.

Due to decreasing availability and rising prices of the premium-quality tonewoods, many manufacturers have begun experimenting with alternate species of woods or more commonly available variations on the standard species. For example, some makers have begun producing models with redcedar or mahogany tops. Some have also begun using non-wood materials, such as plastic or graphite. Most luthiers and experienced players agree that a good solid (as opposed to laminated) top is the most important factor in the tone of the guitar and that solid backs and sides can also contribute to a pleasant sound, although laminated sides and backs are acceptable alternatives. Some jazz players prefer laminated backs and sides.

See Guitar for more details on the construction of acoustic guitars.

Another style of acoustic guitar is the archtop guitar. This incorporates a top, either carved out of solid wood or heat-pressed using laminations, that is arched like instruments in the violin family, usually with f-holes rather than a round sound hole. These guitars are most commonly used by swing and jazz players and often incorporate electronics in the form of a pickup. However, many other kinds of acoustic guitars may incorporate these kinds of electronics as well.

There are several prominent American makers of steel-string acoustic guitars. Martin, Guild, Taylor, and Gibson are known for both the quality and price of their instruments. The Selmer-Maccaferri guitar is an unusual-looking instrument, distinguished by its "D"-shaped or longitudinal oval soundhole. It is usually played by those who follow the style of Django Reinhardt. In Europe, several steel string acoustic guitar makers have gained a worldwide reputation, although their production output is small relative to US and Asian makers. Among the leading European brands are Avalon (Northern Ireland), Brook (UK) and Lakewood (Germany).

Steel-string guitar music and players

Until the 1960s, the predominant forms of music played on the flattop, steel-string guitar remained relatively stable and included acoustic blues, country, bluegrass, folk, and several genres of rock. The concept of playing solo steel-string guitar in a concert setting was introduced by such performers as Davey Graham and John Fahey in the early 1960s, who used country blues fingerpicking techniques to compose original compositions with structures somewhat like European classical music. Fahey contemporary Robbie Basho added elements of Indian classical music and Leo Kottke used a Faheyesque approach to make the first solo steel string guitar "hit" record. Afterwards came Windham Hill Records which brought in elements of Celtic music to join the mix in this now-thriving genre. Today, scores of artists are steel-string soloists, including Al Petteway, Alex de Grassi, Duck Baker, Kaki King, Steffen Basho-Junghans, and Pierre Bensusan. Steel-string guitars are also important in the world of flatpicking, as utilized by such artists as Clarence White, Tony Rice, Bryan Sutton, Doc Watson, and David Grier.

Luthiers have been experimenting with redesigning the acoustic guitar for these players. These flattop, steel-string guitars are constructed and voiced more for classical-like fingerpicking and less for chordal accompaniment (strumming). Luthiers such as Ervin Somogyi, Eric Schoenberg, Kevin Ryan and Stefan Sobell have increasingly focused their attention on the needs of fingerstylists and have developed unique guitars for this style of playing.

Many other luthiers attempt to recreate the guitars of the "Golden Era" of C.F. Martin & Co. Bill Collings, Marty Lanham, Dana Bourgeois, Randy Lucas, Lynn Dudenbostel, and Wayne Henderson are but a few of the luthiers building guitars inspired by vintage Martins, the pre-World War II models in particular. As prices for vintage Martins continue to rise exponentially, upscale guitar enthusiasts have demanded faithful recreations and luthiers are working to fill that demand.

Since its creation, steel string acoustic guitars have evolved as well. Since they use steel strings, guitar manufacturers have built acoustic/electric guitars with magnetic pickups, allowing the sound to be converted into an electrical signal for direct amplification and recording from the instrument. Players can also add distortion or other effects to the electronic signal.

See also

• Twelve-string guitar
• Gibson Dove
• Dingulator