Steel Manufacturing Process

Background

Steel is a metal made from iron ore and has trace amounts of carbon. It is both stronger than wrought iron and less brittle than cast iron. It comes in both alloyed and non-alloyed forms. Non-alloyed steel is basic steel that only contains carbon. Alloyed steel is produced by mixing in additional chemical elements to give the metal specific characteristics. Stainless steel, for example, is made by mixing in a particular percentage of chrome and nickel during the manufacturing process. Professor Joseph S. Spoerl notes that the first process that allowed for the mass production of steel was developed in 1856 by Sir Henry Bessemer. His Bessemer process dominated steel production in the latter half of the 1800's, but was displaced by the open hearth steel production method by the early 1900's. There are presently two steel manufacturing processes in widespread use: the basic oxygen furnace technique and the electric arc furnace.

Iron Production

The first stage of the steel manufacturing process is converting iron ore into molten iron that can be used for steel. There are three methods of making iron. The first method is the coke-oven-sinter blast furnace method. The ore is subjected to sintering, a process that readies the ore for the blast furnace. The iron and coal coke are placed in a blast furnace. The result is molten iron that can be fed into the oxygen furnace or cast as pig iron. An alternate method is direct reduction. Direct reduction involves crushing the ore and using coal, carbon monoxide and hydrogen to remove oxygen and other impurities. This produces a very pure iron called direct reduced iron which can be used in electric arc furnaces. The final method is smelting reduction. There are several smelting processes, but smelting generally involves using coal coke in a gesifier to produce iron from ore.

Steel Production

The first method of steel production involves the basic oxygen furnace. Molten iron, which can come from the smelting process or the blast furnace, is fed directly into the oxygen furnace. The molten iron undergoes decarburization (oxidation of carbon) which results in molten steel. The other available method is the electric arc furnace, which uses scrap steel, direct reduction iron, or pig iron and melts them using an electric arc, which produces molten steel. Both these methods produce crude steel which are processed by continuous casting. This semi-finished steel must be finished into either carbon steel or alloy steel. Carbon steel is re-rolled essentially as is into a desired form. Alloyed steel must be treated with the appropriate chemical elements before being re-rolled.

References

• A Brief History of Iron and Steel Manufacture by Professor Joseph S. Spoerl
• Iron and Steel Manufacturing Process
• Manufacturing Process for Iron and Steel

Resources

• Read this Article in Spanish