Steel: An iron base alloy, malleable under proper conditions, containing up to 2% carbon (seldom exceeds 1.7%). Alloys with high proportion of other elements and a relatively small amount of iron, are still called steel if the iron and carbon are important influencing elements.

Iron is a major component and primary element in steel. Carbon is the major alloying element. 90% of the steels produced through out the world is referred to as carbon steel. Iron weighs 7.86 g/cm³ or 490 /lb/ft³df. melting point of iron is 1535° C (2795° F) and boils at 3000° C (5432° F). It is fourth most abundant element by weight in the crust of the earth and makes up most of the core of the earth. Pure iron is soft, malleable, and ductile and has very useful property of being magnetic. Small amounts of some elements such as manganese, sulphur, silicon, chromium, molybdenum, phosphorus are also added to steel to improve its properties

Iron ores from which iron is extracted are Magnetite, Hematite and Taconite.

Magnetite is combination of ferric oxide and ferrous oxide (Fe₂O₃ & FeO). It is a black ore containing about 15% iron. Magnetite is strongly magnetic.

Hematite is red blood in color and is basically ferric oxide or rust (Fe₂O₃). It is a low grade ore than magnetite and has 50% iron. Taconite is a green low grade core which had 30% iron. Other ores are limonite, siderite, marcesite and iron pyrites.

Limonite ( FeO.H₂O)is a hydrated ferrous oxide. Siderite is ferrous carbonate (FeCO₃) and iron pyrites and marcesite are iron sulphides (FeS). These ores are of poor quality in iron content, often less than 10%.

Carbon exists in small quantity in ferrite and in cementite. Iron and carbon together form a compound called iron carbide (Fe₃C) in which one carbon atom is bonded to three iron atoms. When steel is raised to a red heat and cooled suddenly, it is hardened by the formation of the hard carbide Fe₃C. The eutectic point, or the saturation point of the dissolving of the carbon in the iron is 0.83% above which point the excess carbon is thrown out as free graphite unless other elements are present to take it up.

Some of steels according to manufacturing process

Dirty steel is steel with inclusion of iron oxide from scrap used in the converter or of aluminum oxide from the aluminum used in deoxidizing. The melting point of steel varies with carbon, but is always higher than that of cast iron with the same amount of combined carbon.

Open hearth steel is made by fusing cast iron with steel scrap or wrought iron in a regenerative furnace. Cementation consists of heating bars of wrought iron in contact with carbon. This is called blister steel as surface is covered with Blisters. Blister steel has a crystalline fracture decreasing toward the center of the bar where there is less carbon.

Shear steel is produced from this blister steel by cutting and piling together, heating to a high temperature and rolling or hammering into bars.

Bessemer steel is made by carburizing cast iron by forcing a powerful blast of air through molten iron.

Crucible steel is made by melting wrought iron in a crucible with charcoal and ferromanganese or special steel mixes in a crucible furnace. The slag separates by gravity from the molten steel in the crucibles and the oxides combine with carbon and manganese or aluminum and boil off. The crucible process permits a high degree of control and reduces sulphur and phosphorus.

Electric steel is made in either the induction of arc type furnace and is of uniform quality and of a higher strength and ductility than open-hearth steel of the same carbon content.