The iron and steel industry is made up of hundreds of large and small enterprises that produce a range of products--everything from processed iron ore to steel ingots, sheets, rods, bars, and plates in a number of alloy configurations for a huge variety of end uses. Manufactured, or metallic, iron contains relatively large amounts of carbon and is initially extremely brittle. The carbon content of steel is much lower--usually, less than 1.7%--and the metal is generally more malleable, tougher, and less brittle than iron. In the United States, steel ranks among the ten largest industries. Steel producers fall into two major categories. Integrated steel makers convert iron ore into steel through a lengthy process that employs a blast furnace to produce iron from iron ore, and a basic oxygen or open hearth furnace to transform the iron into steel. Non-integrated steelmakers melt steel scrap in electric arc furnaces to produce liquid steel in facilities that are sometimes referred to as minimills. Given the very large size of many non-integrated steel facilities, however, the term "scrap-based mill" is also used to describe a steel plant that does not convert iron ore to iron; and "ore-based mill" has become another term to describe an integrated steelmaker. In the post-World War II period, the rapid expansion of foreign steel industries created unprecedented competition for the U.S. industry, which, in response, increased its investment in new technologies to reduce costs, improve steel quality, and meet more demanding performance specifications. IRON \Tiron\t is one of the most widely distributed and abundant elements in the Earth's crust, constituting about 5% of the total. In addition to ores that are economically and physically obtainable at present, there are very large quantities of iron-bearing materials from which iron can be recovered as new techniques in mining and ore handling emerge. Iron Ore The development of present iron ore deposits began millions of years ago when most of the world was under water. Immense quantities of sediment, some rich in iron, settled out through the ages. These age-old, iron-bearing marine sediments form the basis of the major usable iron deposits in the world today. After these deposits were incorporated into the crust of the Earth, they were gradually moved closer to the surface by the drift of the continents and the upheaval of sediment layers on the sea bottoms. The ore formed in this way is a mixture of iron oxide and other compounds in varying proportions. In economic terms, iron ore is that part of the total iron in the Earth's crust that is economically available for industry. It is found in chemically combined forms, such as iron oxides carbonates, sulfides, and silicates. Iron ore reserves are found worldwide. Areas with more than 1 billion metric tons of reserves include, in order of decreasing amounts, Australia, Brazil, Canada, the United States, Venezuela, South Africa, India, the \TUSSR\t, Gabon, France, Spain, Sweden, and Algeria. The ore is found in varying grades, ranging from 20% to 70% iron content. North America has been fortunate in its ore deposits, which are found in commercially usable quantities in 22 states in the United States and in 6 Canadian provinces. In the United States the most abundant supplies, discovered in the early 1890s, are located in the Lake Superior region around the Mesabi Range. Other large deposits are found in Alabama, Utah, Texas, California, Pennsylvania, and New York. These deposits, particularly the Mesabi Range reserves, seemed inexhaustible in the 1930s, when an average of 30 million tons of ore were produced annually from that one range. The tremendous demand for iron ore during World War II virtually tripled the output of the Mesabi Range and severely depleted its deposits of high-grade ore. After the war an intensive search revealed large quantities of rich ore, acceptable for blast-furnace use, in newly discovered deposits. Most of these discoveries involved reserves located close to the surface, allowing the use of open-pit mining rather than the more costly underground mining that had been necessary to reach many of the older reserves (see \Tmining and quarrying\t). In addition, new ore upgrading techniques were developed to exploit the large reserves of low-grade ores such as taconites and jaspers. These include sintering and pelletizing. Sintering is used when ore and other iron-bearing materials are too fine to be charged directly into the furnace. These materials are agglomerated with a mixture of coal and coke fines, or powders, which, when ignited, provide the heat for the sinter process. The result is a porous, clinkerlike mass that enhances the upward flow of hot gases through the blast furnace burden. Pelletizing is used to increase the iron content of low-grade (20% to 30% iron) ores. After being crushed, screened, and concentrated, the ore fines are formed into small balls or pellets with an iron content of 60% or more. The pellets are then hardened by heating to increase their strength and durability for subsequent processing. Thus, ores that were once considered to be unsuitable now supply a substantial portion of the industry's requirements. Ironmaking Iron is made by refining iron ore to a point where it reaches 90% to 95% purity. Refining has been achieved in a number of ways through the centuries, dating back as far as the 2d millennium BC. Wrought iron, the earliest form of manufactured iron, was made by heating lumps of iron ore with charcoal. This produced sponge iron, a pasty mix of iron with a great deal of slag, the unwanted residue of the ore-refining process. The iron-slag mixture was hammered into a semifinished bar (hammering expelled some of the slag), and then further worked into finished products. Later, furnaces were devised that could produce enough heat to smelt ore into liquid iron, which was then cast rather than wrought (see \Tmetallurgy\t). The \Tblast furnace\t was developed in Europe in a crude form during the Middle Ages, and has become the principal industrial device for the smelting of iron. The early furnace was essentially a stone stack, some 3 to 4.5 m (10-15 ft) in height. Layers of iron ore, charcoal, and limestone formed the "charge," which was poured through the stack onto a fire on the furnace bed. The limestone acted as a collector of ash and ore residues, forming a slag that could be separated from the smelted iron and discarded. The charcoal was both fuel for the fire and a reducing agent, removing the oxides from the ore. Cold air blown in at the base of the furnace raised combustion temperatures high enough to melt the iron in the ore. By the 17th century \Tcoke\t was beginning to replace charcoal as the primary blast furnace fuel. Made from coal, which was just coming into use in Europe, coke produced higher temperatures than charcoal, and its greater strength permitted larger, heavier charges and encouraged the use of larger, more efficient furnaces. In the United States, with its abundant forests, charcoal continued to be the main furnace fuel until about 1840, when anthracite coal came into use. Coke became the prime fuel only in the 1870s and '80s, and large coke-making facilities soon became necessary adjuncts to the blast furnace. Little change in blast furnace technology took place until the mid-1800s, when it was found that heating the air blast before blowing it into the furnace greatly increased furnace efficiency. The construction of the furnace also changed. The square-based stone stack was replaced by a tall, cylindrical structure made of wrought-iron plates and lined with firebrick. These larger furnaces increased the production of iron considerably. In 1839 the new-style furnaces were reportedly able to produce 28 tons of foundry iron in a week. Stone-structure furnaces were limited to half that tonnage. By 1900 furnaces had grown even larger and were capable of producing more than 200 tons of molten iron per day. During the 20th century significant improvements in blast furnace structure and practice (but not in the basic process) have resulted in tremendous production increases. The blast furnace remains essentially a giant structure with a shell lined with firebrick. It features a furnace stack, which is over 30 m (100 ft) in height and 12 m (40 ft) in diameter at the hearth, and 3 or 4 stoves--used to preheat the air--which are almost as high as the furnace stack. Facilities are also provided for handling and charging iron ore, sinter, coke, and limestone into the top of the vertical stack; as they descend they are met by a rising volume of hot gas formed by combustion of the coke with air preheated to 1,000 C (1,800 F) and blown in under pressure through nozzles called tuyeres, which are located at the base of the stack. The carbon monoxide from the burning coke reduces the iron oxide to iron, while the limestone removes impurities from the ore. At the base of the furnace the molten iron is tapped into submarine-shaped ladles capable of holding 300 tons. The blast-furnace process operates 24 hours a day, 7 days a week. This continuity is essential to efficient operation; if the furnace is shut down, several days are often required before smooth operation is restored. The raw materials are constantly being charged into the top to replace the gasified carbon and the molten products that are removed from the furnace. The furnace is tapped up to 6 times a day, at intervals of 4 to 6 hours. The iron drawn off leaves the furnace in a fiery stream at 1,500 C (2,700 F). The size of the furnace determines the amount drawn off at each tap. For the large, average furnace in the United States producing 5,000 tons per day, each tap yields about 800 tons. The new 10,000-ton-per-day furnaces have 4 tapholes, and the tapping process is almost continuous. The blast-furnace process is one of the most efficient in the industrial world, since 90% of the iron contained in the ore is melted and becomes pig iron, the name for iron that is the product of the blast furnace. Of the other 10%, some goes into slag, and some becomes flue dust that combines with the gas at the top of the furnace. Most of this flue dust is recovered and used in the sintering process. Another significant modern iron-making process produces a material called direct reduced iron, a type of sponge iron. It is produced directly from iron ore oxides in the form of lump ore, pellets, and ore concentrates. Natural gas is used instead of coke as the heating and reducing agent, eliminating the need for large blast furnaces and coke ovens. Impurities are removed as a slag. The resulting metal is free from such residual contaminants as nickel and copper and is therefore in demand for making certain grades of steel in electric furnaces. Direct reduced iron is formed into briquettes for handling and storage. It has a tendency to reoxidize in the presence of any oxygen source, such as water, and must be stored and transported with care. Uses of Iron Until 1870 very little steel was produced either in the United States or in the rest of the world. Iron was the end product, and it had a multiplicity of uses. Perhaps the greatest use was in making railroad rails and railroad car wheels. Because most buildings were relatively small and made from stone, brick, or wood, construction iron was used only to a limited extent until the era of \Tcast-iron architecture\t, beginning in the late 1800s and ending in the latter part of the 19th century, when steel became the primary structural material for large buildings. Iron also had significant uses in the form of nails and wire, pipe, ordnance, hardware, and small machine parts and in sheets plated with tin, which were used for food containers. With the advent of steel most manufactured iron came to be used as the prime raw material for steel making, and that remains its principal application today. Blast-furnace iron that is not converted into steel may be used in foundries to produce castings of such items as water and drainage pipe, construction and heavy machinery parts, and a variety of small parts for the railroad and automobile industries. STEEL PRODUCTION Blast furnace iron contains about 5% carbon, up to 1% of both manganese and silicon, and much smaller but still significant amounts of phosphorus and sulfur. In the steel making process most of the carbon is oxidized along with virtually all the silicon and much of the manganese. Phosphorus and sulfur, which can be detrimental to steel quality, must be also be reduced. With few exceptions, however, manganese is always added to refined steel to increase its strength and ductility. Where there are special performance requirements, a variety of alloys--such as nickel, chromium, molybdenum, and vanadium--are also added during the production process. Steel, which is the result of the refining process, can be defined as relatively pure iron containing less than 1.7% carbon. Although steel has been known for centuries, its production was extremely limited until the invention of the Bessemer process in the late 1850s. Before that time steel was produced in small containers called crucibles or by a process that consisted of placing iron bars in a charcoal furnace. In the crucible process, molten iron was mixed with charcoal and refined in a refractory-lined pot. Production was so limited that the amounts of steel produced were measured in pounds. Statistics from 1860 record some 11 thousand tons of steel produced in the United States, compared to almost a million tons of iron produced in the same year. The Bessemer Process The Bessemer process, which gave birth to the modern steel industry, is a pneumatic process that forces air through a bath of molten iron in a pear-shaped vessel lined with refractory material. The oxygen in the air is brought into contact with the carbon in the iron and reduces the carbon content to the desired level. The process was developed in the late 1850s by the Englishman Henry \TBessemer\t. At about the same time an American, William Kelly, developed a similar process. After a sharp legal contest between the two, Kelly was granted priority by the United States Patent Office, but the dispute was finally resolved by an agreement to merge the two interests. The first Bessemer converter in the United States, a very small vessel capable of producing approximately two tons of steel at one time, was installed at Wyandotte, Mich., in 1864. Acceptance of the process was slow at first, so that by 1870 the annual output of Bessemer steel in the United States was a mere 42,000 tons. Production grew rapidly thereafter, rising to 1.2 million tons in 1880. The principal application of Bessemer steel in the 19th century was for the manufacture of railroad rails, which proved far more durable than iron rails. By the 1890s virtually no more iron rails were being produced. The Open-Hearth Process The open hearth steelmaking process, known in Europe as the Siemens-Martin process, was first introduced in the United States in 1868 (see \TSiemens\t family). Its furnace is a long, narrow, somewhat rectangular structure with an arched roof, lined with refractory brick. A series of doors across the front of the furnace provide access to the shallow basin, or hearth, where raw materials are added, or "charged," and the molten metal is tested during refining. The charge consists of measured quantities of limestone, iron ore, scrap metal, and liquid pig iron. These materials are melted and refined by the action of the long hot flames projected by the gas or oil burners at each end of the furnace. A typical open-hearth shop may have ten or more furnaces operating at the same time. Despite the fact that the open-hearth process took much longer to refine a batch of steel, it was still superior to the Bessemer operation because it could use up to 100% scrap in the charge (the Bessemer converter was limited to 10%), and it could refine pig iron with a high phosphorus content. Access for testing and control was available; and the steels produced contained less nitrogen and were therefore less brittle. Acceptance of the open-hearth was slow until 1895 when nearly 1.3 million tons were produced by this method. By 1908 open-hearth output surpassed Bessemer tonnage; it was so dominant in the ensuing years that by 1950 the open-hearth process made 90% of the U.S. steel output. Bessemer converters produced less than 5%. Basic Oxygen-Furnace Process In the basic oxygen furnace pure oxygen is blown directly on top of a charge in a refractory-lined furnace that is capable of being tilted. The process revolutionized the industry by reducing the time needed to produce a batch of steel from 8 hours, with an open hearth, to less than one hour. This new concept increased productivity, improved yields and quality, lowered refractory costs, and upgraded environmental control. The process was developed in Austria after World War II. In North America the first facilities were installed in 1954. These early furnaces had a capacity of about 35 tons per heat, industry nomenclature for a batch. Heat size has risen gradually to the 300-ton range, with some units even larger. The basic oxygen furnace, roughly resembling the Bessemer converter, is first tilted to receive the scrap and hot metal charge, then brought upright for the blow. An oxygen lance is lowered into the vessel to a point about 2 m (6 ft) above the charge materials. Oxygen under pressure is blown into the furnace for a predetermined length of time, usually 20 to 22 minutes. Consumption of oxygen averages 50 cu m (1,766 cu ft) per ton of steel produced. The time to charge, test, and tap is generally equal to the blowing interval: a full cycle is about 45 minutes. To make a plain carbon steel, a minimum of 70% molten blast-furnace iron in the charge is necessary to satisfy chemical and thermal specifications. The higher the carbon and temperature requirements, the greater the quantity of molten iron that must be in the charge. To ensure an adequate flow of iron for basic oxygen steel making, therefore, substantial capital funds are needed to build and maintain coke-oven and blast-furnace facilities. Since its inception basic oxygen steel making has gained worldwide acceptance. In the United States and abroad the process presently provides about 65% of total steel production. Japan produces slightly more than 70% using the basic oxygen process. The Electric-Arc Furnace The first commercial electric-arc furnace (EAF) steel production took place in France in 1900 and in the United States in 1906. These early furnaces, tiny in comparison with today's EAFs, produced about 4 tons of steel per heat. The EAF is essentially a melting operation, with only a minimal amount of refining. The conventional EAF furnace is a round steel shell lined with refractory brick, with an electrode assembly that pivots out of the way for charging. The EAF uses iron and steel scrap exclusively, although conditions may sometimes warrant the use of direct reduced iron. A large bucket of scrap is charged into the open top of the furnace when the roof assembly has been swung out of the way. With the assembly back in place three carbon electrodes are lowered through holes in the roof until they are in near contact with the charge. When the power is switched on, arc temperatures approaching 3,300 C (6,000 F) produce a rapid melting of the charge. A second bucket of scrap is usually needed to meet the desired heat weight. Oxygen is often used to accelerate scrap meltdown. When the specified steel requirements are met, the furnace is tilted to tap the heat into a waiting ladle. Electric-furnace heat size has gradually increased from an average of 35 tons per heat in the mid-1940s to about 200 tons in 1980, with several units reaching 400 tons per heat. Initially, the EAF process was limited to producing alloy steels. With improved technology, however, carbon steel tonnage grew to match alloy output; by the mid-1980s, the production of carbon steel was three times the alloy tonnage. The EAF process was slow in gaining a significant share of total U.S. production. In 1950 the process made only 6% of total domestic tonnage. By 1990, however, EAF's share had grown to 35%. Europe and Japan experienced similar growth. The newest generation of electric-arc furnaces are high-speed, computer-assisted operations featuring an 8 m (26-ft) diameter steel shell with water-cooled panels in the roof and sidewalls. Ultrahigh power input, using 71-cm (28-in) electrodes, has reduced the steel-making cycle to under two-and-a-half hours. Heat size is around 200 tons. Because the raw material for the EAF process is iron and steel scrap, the capital investment for an EAF facility is relatively small compared with an integrated steel plant, which must convert coal and iron ore to coke and iron before it can begin making steel. The EAF process has therefore proved to be an attractive investment, both in the United States and elsewhere, and especially in developing nations. But the growth of this process--and its increasing ability to produce a variety of steel grades--will be limited by the availability of quality scrap metal and inexpensive electric power. Although a number of integrated plants include EAF shops, more than 50% of the EAF tonnage in the United States comes from small, independent minimills. Minimills represent a very efficient application of the EAF concept. They consist of relatively small plants built at minimal cost, sited near their markets, and offering narrow product lines. Their operations are designed to minimize materials handling and delays; their personnel are usually involved in incentive systems that place strong emphasis on costs and productivity. Steel Refining Immediately after the steel-making furnace is tapped, the ladle of liquid steel, at a temperature of about 1,625 C (2,950 F), is moved to a refining station. Here the steel is stirred using an inert gas such as argon to improve the uniformity of temperature and composition. Levels of sulfur and other impurities in the steel can be decreased further. For high-quality steel grades, vacuum devices remove certain detrimental gases such as hydrogen from the molten steel. After these refining steps are completed, the ladle of steel passes through one of two separate processes, ingot production or continuous casting. Ingot Production The molten steel is released into cast iron ingot molds and allowed to solidify into ingots, tall, tapered rectangular shapes weighing from a ton to 100 or more tons. The molds are then stripped away, and the ingots are placed in a covered pit, the soaking pit, where they are heated to a uniform temperature. The average ingot destined for a rolling mill weighs well under 50 tons, while very large ingots are slated for forging. The heated ingot now passes through the primary rolling mill, a massive set of rollers that reduce the ingot to one of several predetermined shapes. A bloom is a square or oblong shape usually more than 15 x 15 cm (6 x 6 in), and varying in length up to 9 m (30 ft). A slab is a rectangular shape that can vary in width from 50 to 203 cm (20 to 80 in) and in thickness from 5 to 30 cm (2 to 12 in). Blooms are further processed into smaller square sections called billets. Together, blooms, slabs, and billets constitute what is known as semifinished steel. Continuous Casting Continuous casting produces a semifinished form without the intermediate ingot, soaking pit, and blooming or slabbing mill operations. Instead, the ladle of liquid steel from the furnace is discharged into an intermediate, smaller ladle that releases it into a water-cooled copper mold. The partially solidified steel is slowly withdrawn from the mold into a series of rollers that gradually bend the cast material as it changes from a vertical to a horizontal orientation. While the cast steel is still moving, a traveling torch cuts the unit to length. A conventional, continuous-cast slab is 20 to 25 cm (8 to 10 in) thick. After reheating, the slab goes through a series of rolling mills that eventually produce plate and sheet steel. Near-net-shape casting, a recent innovation, uses a thin-slab continuous casting technique that produces a slab 5 cm (2 in) thick, which is then immediately reheated and rolled into thin plate and sheet, saving the additional cost and time associated with the reheating and rolling of thicker slabs. The first continuous-casting units were installed in the United States in 1962. Ongoing research and development has now resulted in a process providing increased productivity, substantial energy savings, lower labor and maintenance costs, and higher yields and quality. By 1990, about two-thirds of U.S. steel tonnage was made by continuous casting; it is anticipated that the total will reach 90% by the end of the century. Worldwide, continuous casting's share of the total output has been and remains higher than in the United States. Alloy Steels Steel alloys combine iron and carbon with carefully designated amounts of other elements in order to make steels with specific properties, such as corrosion resistance, heat resistance, superior strength, or the ability to be formed into complex shapes. Constructional alloy steels are designed to produce very high strength structural parts for use in vehicles, on bridges, and in machinery. In addition to manganese, which is added to virtually all grades of steel, relatively small additions of silicon, titanium, vanadium, or columbium can significantly upgrade the physical properties of plain carbon steels to produce low-alloy, high-strength steels. Copper may be added for better resistance to corrosion. The addition of sulfur can improve machinability. Larger amounts of nickel, chromium, molybdenum and vanadium can produce higher-strength steels. With high-alloy grades the alloying elements, including cobalt and tungsten, can often exceed 50% of total steel content. \Lstainless steel\ls rely on their chromium content for their high strength, corrosion resistance, and ductility. Costly high-alloy tool steels are used to make cutting edges for tools that machine iron and steel parts. Usually formulated in the steel-making process, alloy steels may also be produced directly from carefully graded steel scrap in electric arc furnaces, or indirectly, from carbon steel that is remelted in an EAF, along with the alloying elements. SHAPING AND FINISHING Semifinished steel--in the form of ingots, billets, blooms, or any of the semifinished products of continuous casting--is reheated to a temperature of about 1,200 C (2,300 F) and is then processed into finished steel products in a variety of rolling mills. The most important of these are the flat-roll mills, which produce steel strip, sheet, and plate. Flat-Roll Mills The rolls in flat-roll mills are smooth-faced, in contrast to the grooved rolls used to produce shaped products in structural and shaping mills. Heated, semifinished steel is first passed through the hot-strip rolling lines, a series of consecutive stands, each containing huge rolls that squeeze the steel until it is reduced to less than 3.175 mm (1/8 in) in thickness while being stretched in length to over 900 m (3,000 ft). This ribbon of steel is produced at the rate of 1,200 m (4,000 ft) per minute. When it comes off the milling stands, it is coiled and allowed to cool. Uncoiled, the strip is cleansed of its surface oxides in an acid bath. Hot-strip coils may be further thinned, smoothed, and strengthened in a cold-strip line, which can thin them down to 1.588 mm (one-sixteenth of an inch) or less. Because cold rolling produces a stronger but stiffer metal, the coils must be heated in an annealing furnace to make them more malleable, then retempered to impart the desired degree of stiffness. Some coils are coated with zinc and sold as galvanized (non-rusting) sheet metal; others are painted, or plated with tin for use as cans and containers. In making plate a heated slab is passed back and forth between rolls that are capable of producing plate thicknesses from 4.6 mm (0.18 in) to 38 cm (15 in), and in a variety of lengths and widths. Plate is used in applications ranging from ship and railroad-car construction to oil and gas pipeline. Structural and Shape Mills Blooms, billets, and in some cases ingots may be rolled directly on mill rolls that have been grooved and shaped to produce specific steel products--rails, bars, rods, pipe and tubing, and structural steel such as the "I" and "H" beams used in building construction. Rails are rolled from heated blooms that must meet stringent dimensional and quality specifications. Primary uses are for railroads and crane runways. Bar mills use billets to produce a wide variety of steel products and shapes--for example, concrete-reinforcing bars for construction, cold-finished bars for the manufacture of machines and machine tools, and round bars, squares, and hexagons. As many as 20 consecutive mill stands may be used to produce a single shape. Billets may be rolled into wire rods about 13 mm (1/2 in) in diameter and more than 5,000 m (16,500 ft) in length. Wire-rod trains of 17 to 26 stands are capable of finishing speeds as high as 6,000 m (20,000 ft) per minute. The rod is formed into coils, which are drawn through dies to produce wire. Tubular products are shaped in two different ways. Some pipe is formed from strip or plate that is shaped into cylindrical form on "U" and "O" presses. The pipe seam is then welded. Seamless pipe begins with a billet that is rolled into a round, solid section called a tube round. The center of the round is pierced by a cylindrical mandrel bar; the hollowed out, heated tube is then brought to the required diameter and wall thickness on a series of rolls. Seamless pipe is used where great strength is needed, as in oil-well drilling, or, as in steam boilers, where high pressures are involved. Forging Forging consists of hammering and pressing steel that has been heated to a very high temperature. (Unheated steel is cold-forged to mass-produce such items as bolts.) The hammering and squeezing that is part of the forging process "kneads" steel into a denser, stronger structure. Hydraulic presses forge huge, heated steel ingots into very large, tough components such as the massive shafts used in power-generating turbines. Smaller parts are formed by steam-hammering heated steel in dies or by extruding the steel through an opening in a die. In \Tcasting\t, molten steel is poured into a mold where it solidifies in the desired shape. THE STEEL INDUSTRY From the late 19th century until the years following World War II the U.S. steel industry was the largest in the world, at times manufacturing over half the world production of the metal. After World War II, however, both Europe and Japan rebuilt their steel plants from the ground up, replacing old furnaces with newer, more efficient technologies and operating their industries, often, with the help of government subsidies. Eventually, other newly industrialized countries (for example, China, Brazil, South Korea) built their own industries and, combining efficiency with low wages, underpriced U.S. steel in every market, including the United States itself. Recessions in the 1970s and '80s shrank the growth in world steel demand. In the United States the expansion of the scrap-based minimill side of the industry increased the pressure on the old-line integrated mills, and U.S. capacity was reduced from a peak of an annual 160 million tons to 115 million tons in the early 1990s. Industry employment also dropped from a peak of 560,000 to 170,000. For the industry's future, analysts point to new technologies that will produce quality steel more cheaply and without negative environmental effects. Among anticipated technological advances in the near future, the overall productivity of basic oxygen-furnace steel making will be improved with new bottom-blowing and ladle-refining techniques. Coke making, a difficult process to control environmentally, will be fitted with advanced control systems. Coke needs will be reduced by using new methods for injecting coal and other fuels. As electric-arc-furnace steel is used for more demanding applications, scrap-based steel making techniques will improve. Efforts to reduce residual copper, tin, and other unwanted elements in scrap metal have already produced the use of scrap substitutes such as direct-reduced iron. Efforts to reduce energy consumption in electric-arc furnace steel making have produced new techniques, such as the use of hot exhaust gases from the furnace to preheat scrap metal, and new tools, such as the energy optimization furnace, a steel-making facility designed to accept a charge varying from 100% liquid iron to 100% scrap. Advances in continuous casting have almost achieved the goal of near-net-shape casting, which would completely eliminate the need for hot-strip mills to produce many grades of sheet steel. New technology will also succeed in increasing the strength of sheet steel during the forming and paint-baking process and in developing new coatings that will vastly improve corrosion resistance. The production of coke is perhaps the most economically and environmentally sensitive aspect of steel making. Over one-third of the industry's coke plants are nearing the end of their useful lives. It will be extremely costly to replace them with new plants whose control systems are able to meet stringent emissions standards. One potential solution is a new technique known as direct steel making, which eliminates the need for coke. Instead, iron ore and scrap metal are mixed with ordinary coal in a bath of molten iron. The coal acts both as a fuel and as an oxygen reductant. Steel that is made in this manner usually needs further refining, but it is produced without coke. Other processes that have been put in place to produce steel without negative environmental effects include the recapture of furnace effluents; the recirculation, cooling, and filtering of the water used in the production process; the management and disposal of production wastes; and advanced techniques for noise abatement. Richard M. Hurd and Lewis I. Fried Bibliography: Barnett, D. F., and Crandal, R. 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