Steel making:

Steel making:

After iron is obtained either from blast furnace in liquid / melt form (pig iron) or from DRI (sponge iron) process; it is sent for steel production. The iron that emerges from the blast furnace contains 4 - 4.5 % carbon by wt., and other impurities which makes the metal too brittle for most engineering applications. The Basic Oxygen Steelmaking (BOS) process takes this liquid iron plus recycled scrap steel, and reduces the carbon content to between 0 and 1.5% by blowing oxygen through the metal.

Steel is generally made by the Bessemer, Siemens Open Hearth, basic oxygen furnace, electric arc, electric high-frequency and crucible processes.

In Bessemer (BOS) process molten pig iron is refined by blowing air through it in an egg-shaped vessel, known as a converter. In the Siemens process, the necessary heat for melting and working the charge is supplied by oil or gas. Both the gas and air are preheated by regenerators. The regenerators are chambers filled with checker brickwork, brick and space alternating.

The high nitrogen content of Bessemer steel is a disadvantage for certain cold forming applications and continental works have, in recent years, developed modified processes in which oxygen replaces air.

The least costly method of making steel uses scrap metal as its base. Steel scrap from many sources—such as old bridges, refrigerators, and automobiles—and other additives are placed in an electric arc furnace, where the intense heat produced by carbon electrodes and chemical reactions melts the scrap, converting it into molten steel.

Most of these steel plants have finishing mills on site that convert iron and steel into both finished and intermediate products. Some of the goods produced in finishing mills are steel wire, pipe, bars, rods, and sheets. While wire, steel reinforcing bars, and pipes are considered finished products, rolled steel is intermediates, meaning it is normally shipped to companies, such as automotive plants, that stamp, shape, and machine the rolled steel into car parts. In these finishing mills, products also may be coated with chemicals, paints, or other metals that give the steel desired characteristics for various industries and consumers.

Steel manufacturing is an intensely competitive global industry. By continually improving its manufacturing processes and consolidating businesses many of the steel companies increased productivity sufficiently to remain competitive in the global market for steel.