Steelmaking

Steel manufacturing is one of the most important metal industries. In the United States, the annual consumption of steel is well above 1(X) million tons. Steel is an iron alloy that contains from 0.03 to 1.4 percent carbon plus various amounts of other elements. The wide range of useful mechanical properties associated with steel is primarily a function of the chemical composition and heat treatment of a particular type of steel. 

Whereas the production of iron is basically a reduction process (converting iron oxides to metallic iron), the conversion of iron to steel is essentially an oxidation process in which the unwanted impurities are removed from the iron by reaction with oxygen gas. One of several methods used in steelmaking is the basic oxygen process. Because of its ease of operation and 

On the other hand, if manganese is the main impurity, then an acidic flux such as Si02 is needed 

The properties of steel depend not only on its chemical composition but also on the heat treatment. At high temperatures, iron and carbon in steel combine to form iron carbide (Fe3C), 

Heating the steel to some appropriate temperature for a short time and then cooling it rapidly in order to give it the desired mechanical properties is known as tempering. In this way, the ratio of carbon present as graphite and as cementite can be varied within rather wide limits. Table 23.3 lists the composition, properties, and uses of various types of steel. 

Consideration of the Ellingham diagram for oxides (Fig. 17.9) shows that, at the high temperatures prevailing near the tuyeres, coke may reduce silica to silicon (mp 1410 °C)  

The reactions occurring in the molten iron/lime mixture are 

and C will react preferentially with O2 before oxidation of the 

Some 3,000,000 metric tons of O2 are used annually for steelmaking in the United States alone. This practice has the following advantages which more than compensate for the extra cost  

On the other hand, the exhaust gases from BOP converters contain relatively large amounts of red a-Fe20s dust this, however, can be trapped by electrostatic precipitation or water scrubbing and recycled, and the exit gases can be scrubbed with water to reduce air pollution. 

The molten steel is sampled at intervals. When the desired blend of carbon and other impurities has been reached, the vessel is rotated to a horizontal position so that the molten steel can be tapped off (Fignre 23.5). 

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Steelmaking dust Steel mtridation Steel quenching Steel Recycling Institute Steel reinforcing Steel RG-H process H steels Steels... 

Most of the acid-grade spar used for HF production ia the United States is imported. More than two-thkds of the fluorspar consumed ia the United States goes iato production of HF nearly 30% is consumed as a flux ia steelmaking and the remainder is consumed ia glass manufacture, enamels, welding rod coatings, and other end uses or products (see Fluorine compounds, inorganic-calcium). 

Fig. 1. A cut-away schematic of a typical a-c open-arc, steelmaking, eccentric bottom tapping (EBT) furnace.

ATME Electric Furnace Steelmaking, Vol. 1, Wiley-Interscience, Inc., New York, 1962, pp. 153—174. 

Pure iron is a silvery white, relatively soft metal and is rarely used commercially. Typical properties are Hsted in Table 1. Electrolytic (99.9% pure) iron is used for magnetic cores (2) (see Magnetic materials, bulk). Native metallic iron is rarely found in nature because iron which commonly exhibits valences of +2 and +3 combines readily with oxygen and sulfur. Iron oxides are the most prevalent form of iron (see Iron compounds). Generally, these iron oxides (iron ores) are reduced to iron and melted in a blast furnace. The hot metal (pig iron) from the blast furnace is refined in steelmaking furnaces to make steel... 

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