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Steel is made from iron and carbon. Cast iron is a hard, brittle material that is difficult to work, whereas steel is malleable, relatively easily formed and versatile. On its own, iron is not strong, but a low concentration of carbon – less than 1 percent, depending on the kind of steel – gives steel strength and other important properties.
Instead of using natural draught, air was pumped in by a trompe, resulting in better quality iron and an increased capacity. This pumping of air in with bellows is known as cold blast, and it increases the fuel efficiency of the bloomery and improves yield. They can also be built bigger than natural draught bloomeries.
The modern steel industry is one of the largest manufacturing industries in the world, but also one of the most energy and greenhouse gas emission intense industries, contributing 8% of global emissions. [2] However, steel is also very reusable: it is one of the world's most-recycled materials, with a recycling rate of over 60% globally. [3]
Roasting heats the ore in the presence of oxygen from air, oxidizing the ore and liberating the sulfur as sulfur dioxide gas. Smelting most prominently takes place in a blast furnace to produce pig iron, which is converted into steel. Plants for the electrolytic reduction of aluminium are referred to as aluminium smelters.
Finally, the basic oxygen process was introduced at the Voest-Alpine works in 1952; a modification of the basic Bessemer process, it lances oxygen from above the steel (instead of bubbling air from below), reducing the amount of nitrogen uptake into the steel. The basic oxygen process is used in all modern steelworks; the last Bessemer ...
Pig iron, also known as crude iron, is an intermediate good used by the iron industry in the production of steel. It is developed by smelting iron ore in a blast furnace . Pig iron has a high carbon content, typically 3.8–4.7%, [ 1 ] along with silica and other dross , which makes it brittle and not useful directly as a material except for ...
Tempering is most often performed on steel that has been heated above its upper critical (A 3) temperature and then quickly cooled, in a process called quenching, using methods such as immersing the hot steel in water, oil, or forced-air. The quenched steel, being placed in or very near its hardest possible state, is then tempered to ...
One important furnace application, especially in iron and steel production, is smelting, where metal ores are reduced under high heat to separate the metal content from mineral gangue. The heat energy to fuel a furnace may be supplied directly by fuel combustion or by electricity. Different processes and the unique properties of specific metals ...