United States, most of the steelmaking processes are basic rather than acidic because of the low phosphorous content in domestic ores. In Europe, phosphorous is much more common and acidic processes are necessary there.

For many years the open hearth process was the most widely used method of steelmaking in the United States. In 1959 it accounted for 87.5 percent of U.S. steel production, but by 1973 it had dropped to 26.4 percent (Table 1). This drop in steel production was more than offset by output from basic oxygen furnaces which rose from 2 percent of the total in 1959 to 55 percent in 1973. It had proven to be cheaper and faster, required less space and produced steel of quality comparable to that produced by other methods. Most other countries are also converting to the basic oxygen process. The rise in the importance of the electric furnace is not as great in volume as that of the basic oxygen furnace, but because of its high utilization of scrap may be of particular significance in the future.

Steelmaking requires a large amount of raw materials. The production of one ton of steel, for example, requires on the average about 21⁄2 tons of iron ore, coal, limestone, and scrap. With world steel production over 640 million tons, this means that over 1,600 million tons of raw materials are consumed in the process.

Year

1973.

1972

1971

1970

1969.

1968.

1967.

1966.

1965

1964. 1963.

1962.

1961

1960

1959.

TABLE 1.-RAW STEEL PRODUCTION AND INDEX BY TYPE OF FURNACE

1 Based on average production of the year 1967 as 100.

* Included with open hearth.

Source: American Iron and Steel Institute, Annual Statistical Report, 1973, p. 53.

The following is a glossary of terms, grades, and specifications used in the iron and steel industry:

Definition of Terms, Grades, and Specifications

Iron ore is a mixture of iron oxide minerals with varying quantities of mineral impurities. It retains its identity through various processing procedures to ultimate use. Before treatment, it is called crude ore. After processing to improve its quality it is called usable ore.

Hematite, magnetite, and limonite or geothite categorize iron ores identified by color; these mineral ores are called respectively, red, black, and brown ores. Siderite is occasionally identified as brown ore also. Taconite was first used locally in Minnesota to name hard, siliceous, banded rocks of the local iron-bearing formations. Over the last 20

years it has come to be used to identify similar material in other districts.

Partly altered taconite that is soft, and from which part of the silica has been leached by natural processes; is called semitaconite.

Jaspilite, a locally named iron formation rock of Michigan, and itaberite, a rock of Brazil's Minas Gerais district, identify iron ores similar to taconite and are similarly used names.

Iron ore pellet is a class of iron ore that is priced according to its iron content as measured in long ton units.

Pig iron is the product of the blast furnace formed by smelting iron ore with carbonaceous material as the reducing agent, usually in the form of coke. About 90 percent of the pig iron produced in the United States is consumed in making steel; the remainder is used for iron castings. Hot metal refers to molten pig iron.

Cast iron is an iron containing carbon in excess of the solubility in the austenite that exists in the alloy at the eutectic temperature. Gray iron is cast iron containing 2 to 4 percent combined and free carbon. Malleable iron is white cast iron, annealed to graphitize all or part of the cementite. Ductile iron is cast iron that has been treated to give the primary graphite a nodular or spheroidal form.

Ingot iron is commercially pure iron made in an open hearth furnace. Iron powder is iron in finely divided form, commonly made by reduction of finely ground oxide or atomization of molten iron.

Steel is a refined iron-base alloy containing up to 2.5 percent carbon. There are six principal types of steels: (1) plain carbon, (2) full alloy, (3) stainless, (4) high-strength, low-alloy, (5) heat-resistant, and (6) electrical.

Home, revert, or runaround scrap is produced within the iron and steel mills and is circulated back to the furnace for remelting. Purchased scrap, which refers to all types obtained outside the iron and steel industry, is subdivided into prompt and all other. Prompt industrial scrap is the waste material generated from fabricating iron and steel products. Other industrial scrap includes material that has been discarded because it is worn out, obsolete, or rejected for other reasons.14

II. CHANGES IN IRON AND STEEL PRODUCTION

A. Technology

Technological improvements have greatly increased the efficiency of iron and steel production in the last 25 years. The increasing quality of iron ore has particularly improved blast furnace performance. The average U.S. furnace in 1950, for example, required 51 percent more coke and 82 percent more limestone and dolomite per ton of hot metal than is required today.15

Sinter and pellets now provide over 75 percent of the furnace charge, as shown in Figure 1. In 1955 that figure was only 22 percent, with less than 2 percent in the form of pellets. With higher iron content in the ores, with lower coke rates, and with lower slag volumes, blast furnaces produced 33 percent more per unit of hearth area. In addition to the savings in capital investments and operating costs, the higher iron content of the ores has significantly lowered transportation costs because less waste is being moved.

14 Ibid., p. 293.

15 Barber, James R., and Roger D. Brackett. Trends in Iron Ore and Coal Mining. Mining Congress Journal, February 1974: 79.

SOURCE.-James R. Barber and Roger D. Brackett. Trends in Iron Ore and Coal Mining. Mining Congress Journal, February 1974, p. 80.

The direct reduction of iron ore to pellets also has several other advantages that make it important to the future of the iron and steel industry.16 First, there is a world shortage of metallurgical coal and less would be required with direct reduction. Second, many coke ovens have had difficult air pollution problems but direct reduction could reduce the demand for coke and the pollution that would otherwise have resulted. Third, the capital investment requirements for blast furnaces and coke ovens have risen substantially, whereas pellets can be used in electric furnaces at generally lower costs.

Many producers are investing in direct reduction processes and electric furnaces, and very few are building coke ovens and blast furnaces. The cost of direct reduction-electric furnace combinations has been estimated to be about 40 percent less than blast furnace-basic oxygen complexes." The limited availability and high cost of electricity is perhaps the most uncertain aspect of this type of development and may delay its implementation.

16 Hogan, William T. The 1970's: Critical Years For Steel. Lexington, Heath and Co. (1970), p. 37. 17 Ibid., p. 38.

Several other refinements in steel production have been developed in recent years. Continuous casting has proved to be a very efficient method of steel-making which allows several major steps to be bypassed, thereby increasing production speed and lowering costs. Vacuum degassing has facilitated the elimination of impurities in steel, and new high-speed rolling mills have greatly increased the rate of production. Many new mills are computer-controlled to maximize the efficiency of steelmaking operations. The development of the jet piercer in the 1950's was significant because it made it possible to drill holes in the hardest magnetic taconites. These piercers are capable of cutting large, deep holes for heavy blasting charges. Use of this equipment rejuvenated the domestic iron industry. In recent years, however, rotary drills have become more powerful and more predominant. The cost per hole is usually less with rotary drills and low cost ammonium nitrate blasting agents can be used with them. Further development of drilling techniques may make it economically feasible to recover ores that were previously too expensive to mine.

B. Recycling Potential

Secondary sources of iron and steel are very important in steelmaking. In recent years, the percentage of scrap used in furnaces has declined as basic oxygen converters replaced open hearth units. About 44 percent of the charge in an open hearth furnace is scrap, whereas it is only 29 percent in a basic oxygen converter.18 This downward trend is likely to be reversed by the advent of electric furnaces which can use nearly 98 percent scrap. Most of the scrap (60 percent) used is generated in the steelmaking process. The rest is either industrial scrap (15 percent) or obsolete material (25 percent). In addition, relatively large amounts of iron ore are discarded in municipal waste, which averages 7 percent ferrous material by weight before incineration and 30 percent after.19 Each year over 35 million tons of ferrous material are discarded in the United States, of which only 16 million tons are recycled. Most of that amount consists of auto hulks.

Scrap is especially desirable as a raw material because it is already a refined product. The energy required to convert scrap to steel is only about one-third as much as for steel made from iron ore. It normally takes at least two tons of ore to make one ton of steel, because of the waste material chemically combined with the iron in the ore. It has been estimated that of the 18.4 million tons of unrecycled steel products discarded in 1970, 37 million tons of ore and 20 million tons of coal could have been conserved.20

In 1970 less than half of the obsolete scrap was consumed by the steel industry, 16.6 million tons out of 35 million available. The unused fraction has been primarily a result of economics reflected in high transportation costs, depletion allowances for raw materials, the scattered sources, high processing costs, the limited availability of municipal recycling systems, and industry reluctance." Economics have begun to shift in favor of recycling scrap, however, because it already represents a large energy investment.

18 Reno and Brantley, op. cit., p. 300.

19 Cannon, James. Steel: The Recyclable Material. Environment, November 1973: 11:

20 Ibid., p. 12.

21 Ibid., p. 13.

The development of the electric furnace is expected to greatly affect the recycling potential of discarded iron and steel. In 1959 electric furnaces produced only 9 percent of the total steel output; by 1973 that figure had risen to 18 percent (Table 1). In addition, many small plants with capacities between 50,000 and 250,000 tons per year are being built which will utilize local scrap sources, meet local needs, and reduce the transportation cost of both raw materials and finished products. Electric furnaces may provide 30 percent of U.S. steel capacity in 1980 and 50 percent in 1990, according to some estimates.22 In that event, a much higher percentage of available scrap would be required to support furnace operations.

Technological progress has also been made in increasing the amount of scrap that can be used in basic oxygen furnaces. Preheating the scrap to 1400 degrees F., about half the normal operating temperature of the furnace, increases the scrap capacity of the furnace to 40 percent instead of the normal 30 percent capacity. In Japan and Europe preheating is already common, but it has not yet been adopted on a large scale in the United States. Preheating the existing furnaces would permit use of an additional 6.3 million tons of scrap each year. It has also been discovered that injection of oxygen through the bottom of a furnace raises the temperature to a level which allows 20 percent more scrap to be consumed and which facilitates the installation of pollution control equipment.

The major drawbacks to increased use of scrap have been contamination and availability. Variations in the quality of scrap steel, impurities, and the presence of other metals, such as copper, produce undesirable effects in finished steel. Scrap availability has been a problem because of foreign demand, partly as a result of price controls and the dollar devaluations which made domestic scrap attractive to foreign buyers. It is believed that there are 750 million tons of scrap in the United States that could be recycled and which would greatly reduce the need to import foreign iron ore. A recent study by Batelle Institute, however, cited several factors which are inhibiting the use of scrap: 23

(1) Present scrap markets are retarded because of transport rates which encourage the usage of iron ore; (2) future scrap markets are being affected because new investment that would logically be directed to scrap-intensive steelmaking is diverted because of the existing freight rate structure to ore-intensive steelmaking; (3) iron ore (a limited domestic natural resource) is being exploited, when it can and should be conserved; and (4) some scrap iron that should be recycled is unable to move; thus the environment is despoiled by unnecessary accumulations of solid metallic waste.

C. Environmental Problems

The iron and steel industry, as already suggested, is confronted with major environmental problems which could eventually restrict supply. Few of these problems are generated by the mining and beneficiation operations, although one large taconite processing plant was closed temporarily because of the high asbestos content of the tailings it was dumping into Lake Superior. In areas where iron ore is strip mined, reclamation will add considerably to mining costs.

za Ibid., p. 13.

2 Ibid., p. 16.