Type of Carbon Steel

Mild and low carbon steel
Mild steel is the most commson form of steel as its price is relatively low while it provides material properties that are acceptable for many applications. Low carbon steel contains approximately 0.05–0.15% carbon[1] and mild steel contains 0.16–0.29%[1] carbon, therefore it is neither brittle norductile. Mild steel has a relatively low tensile strength, but it is cheap and malleable; surface hardness can be increased through carburizing.

It is often used when large amounts of steel is needed, for example as structural steel. The density of mild steel is 7,861.093 kg/m³ (0.284 lb/in³), the tensile strength is a maximum of 500 MPa (73,000 psi) and the Young's modulus is 210,000 MPa (30,000,000 psi). Low carbon steels suffer from yield-point runout where the materials has two yield points. The firstyield point (or upper yield point) is higher than the second and the yield drop dramatically after the upper yield point. If a low carbon steel is only stress to some point between upper and lower yield point then the surface may develop luder band.

Higher Carbon Steel
Carbon steels which can successfully undergo heat-treatment have a carbon content in the range of 0.30–1.70% by weight. Trace impurities of various other elements can have a significant effect on the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short. Low alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melts around 1426–1538 °C (2600–2800 °F).[4] Manganese is often added to improve the hardenability of low carbon steels. These additions turn the material into a low alloy steel by some definitions, but AISI's definition of carbon steel allows up to 1.65% manganese by weight.

Approximately 0.30–0.59% carbon content. Balances ductility and strength and has good wear resistance; used for large parts, forging and automotive components.

Approximately 0.6–0.99% carbon content. Very strong, used for springs and high-strength wires.

Approximately 1.0–2.0% carbon content. Steels that can be tempered to great hardness. Used for special purposes like (non-industrial-purpose) knives, axles or punches. Most steels with more than 1.2% carbon content are made using powder metallurgy.

Steel can be heat treated which allows parts to be fabricated in an easily-formable soft state. If enough carbon is present, the alloy can be hardened to increase strength, wear, and impact resistance. Steels are often wrought by cold working methods, which is the shaping of metal through deformation at a low equilibrium or metastable temperature.

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