Uses of Iron and Steel. Iron and Steel Production and the Environment

The widespread use of iron arises not only from its abundance but also from the range of services it can perform. Wrought iron, the earliest form used, is malleable and was traditionally the material smiths forged and welded into complex shapes. Today most products called "wrought iron" are actually made of steel. So- called "mild" steel, which contains up to about 0.5 percent carbon, is made in large quantities and used in buildings, bridges, motor vehicles, and machinery of all kinds.

Tool steel contains 0.5 to 1.2 percent carbon and can be hardened by quenching and tempering. Although made in relatively small quantities, it is the essential material used in tools for mining, smelting, and the shaping of metals, stone, and nearly all other materials. Alloy steels develop special properties through additions of relatively scarce metals such as chromium, manganese, molybdenum, or vanadium. Chromium and nickel, for example, give stainless steels their remarkable resistance to corrosion.

Iron alloyed with 1.2 to 4 percent of carbon, known as cast iron, can be easily melted and poured into moulds. From early modern times to very recently it was cast iron that allowed nearly everyone to have pots, pans, and related equipment in their homes. The nineteenth century saw cast iron used to create a distinctive style of architecture for commercial buildings. Because iron foundries find it increasingly difficult to comply with modern air pollution and workplace regulations, relatively few remain active in developed countries. Consequently, many items formerly made of cast iron are now made of steel.

Iron and Steel Production and the Environment. The production and use of iron is relatively benign compared to the deleterious effects on the environment that arise from the use of other metals. Unlike the nonferrous metals, which are extracted from sulfide minerals, iron is made from oxide ores. Therefore, iron mining does not cause problems with acid mine drainage and the release of toxic substances, such as arsenic and sulfur fumes, associated with mining and smelting of metals such as copper, lead, and zinc, which all are extracted from sulfide minerals.

Nevertheless, the sheer scale of the iron industry guarantees significant environmental consequences. The exhausted iron mines of northern Minnesota, Michigan, and Wisconsin are now huge holes in the ground. Old mining communities sometimes try to use them as a tourist attraction. Fortunately, slag, the principal solid waste left from ironmaking, can be recycled as aggregate for concrete.

Making large quantities of iron requires large quantities of fuel. Ironmakers' heavy demands on the forest resources of England beginning in Tudor times led them to develop coppicing as a forest management technique. With coppicing, trees are cut down but their stumps are left behind. These then spout many new shoots, which are allowed to grow to a certain size and then harvested. The process can be repeated, assuring a continuous yield of wood.

Trees grew to a size suitable for making charcoal in about twenty years. By managing enough acreage of forest so that a twentieth of it was cut each year, an ironmaker secured a continuous fuel supply. Large tracts of woodland held by ironworks in the eastern United States form the nucleus of many of today's state forests.

Beginning in about 1800, substitution of mineral coal for charcoal as the primary fuel for ironmaking initiated the rapid expansion of iron and steel production that we associate with the Western industrial revolution. The sulfur and tar in mineral coal became a source of air and water pollution wherever coke for steelworks was made.

Recycling unwanted iron products is long- established practice, and is the source of nearly half of the steel made in the U.S. today. Mechanized equipment for shredding products such as motor vehicles has increased recycling rates and helped remove junkyards from the landscape. Increased recycling allowed a major restructuring of the steel industry from 1980 onward.

New minimills melt scrap steel in electric arc furnaces and roll their recycled steel into the sheets and plates that are the products now most in demand. These mills have freed themselves from the inflexible management practices and restrictive work rules that made the older, established steelworks unprofitable. As a result, many no-longer-useful steelworks are large brownfield sites in urban areas of the industrialized nations.