Arnold Bergini, age 15, of White Plains, N.Y., for his question:
WHAT IS USED TO MAKE STEEL?
Steel is an alloy or mixture of iron and small, definite amounts of carbon and other minerals. Steel is stronger than iron and can be shaped into many more useful products.
Pig iron contains as much as 5 percent carbon and other impurities. Therefore, the steel making process is largely one of removing the excess carbon and impurities from iron and adding desired materials in carefully controlled amounts.
Scrap iron and scrap steel provide important raw materials in steelmaking. Scrap metal is remelted and then again it becomes useful. The iron and steel industry in the United States uses about 85 million tons of scrap each year.
Making steel requires a number of different raw materials that is gathered from many states and countries. These materials range from aluminum to zirconium, but the carbon from coke is the most important.
To make steel, a mill may require iron ore from Minnesota, limestone from Michigan, coal from West Virginia, manganese from Brazil, fuel oil from Texas, scrap iron from Oklahoma, magnesite from Washington, dolomite from Oregon and ferrosilicon from New York.
The steel used in a single automobile gear may require 15 raw materials from five different continents.
The properties of different kinds of steel may be improved by various combinations of heating and cooling, called heat treating. This is a series of operations in which the steel product is heated to a high temperature, rapidly cooled in oil or water and then tempered or reheated to a lower temperature to secure the proper combination of strength and ductility.
Steel companies actually make thousands of different kinds and forms of steel.
Some of the most widely used alloy materials used in steel include chromium, nickel, manganese, molybdenum, tungsten and vanadium.
Steel is made in an open hearth furnace. An open hearth furnace has a saucer shaped floor or hearth. The furnace is open directly to the flames that melt the steel. The furnace is lined with fire resistant brick, which is held in place by heavy structural steel.
Underneath the hearth is a checkerboard arrangement of firebrick through which heated fuel and air flow. The fuel may be blast furnace gas, oil, tar or any of these combined. The fuel burns above the hearth. The furnace heats to about 3,000 degrees Fahrenheit.
Each open hearth furnace is about as big as a two story house. A steel plant usually has several open hearth furnaces in one long building, all facing in the same direction.
The furnaces are filled through doors along one side. The steel is tapped from the opposite side where the floor of the building is one story lower. Each batch of steel made in a furnace is called a heat. A heat generally consists of 100 to 300 tons of steel and takes from five to eight hours to make. A steel worker called a welter is in charge of several furnaces.