carbonl content influences the yield strength of steel because they fit into the interstitial crystal lattice sites of the body-centered cubic arrangement of the iron molecules. The interstitial carbonl reduces the mobility of dislocations, which in turn has a hardening effect on the iron. To get dislocations to move, a high enough stress level must be applied in order for the dislocations to "break away". This is because the interstitial carbonl atoms cause some of the iron BCC lattice cells to distort.
Types of carbonl steel

Mild (low carbonl) steel: approximately 0.05–0.29% carbonl content Mild steel has a relatively low tensile strength, but it is cheap and malleable; surface hardness can be increased through carburizing   
Medium carbonl steel: approximately 0.30–0.59% carbonl content(e.g. AISI 1040 steel). Balances ductility and strength and has good wear resistance; used for large parts, forging and automotive components.
High carbonl steel: approximately 0.6–0.99% carbonl content]. Very strong, used for springs and high-strength wires.
Ultra-high carbonl steel: approximately 1.0–2.0% carbonl 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% carbonl content are made using powder metallurgy and usually fall in the category of high alloy carbonl steels. steel can be heat-treated which allows parts to be fabricated in an easily-formable soft state. If enough carbonl 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.

Metallurgy

Mild steel is the most common form of steel as its price is relatively low while it provides material properties that are acceptable for many applications. Mild steel has a low carbonl content (up to 0.3%) and is therefore neither extremely brittle nor ductile. It becomes malleable when heated, and so can be forged. It is also often used where large amounts of steel need to be formed, for example as structural steel. Density of this metal is 7,861.093 kg/m³ (0.284 lb/in³), the tensile strength is a maximum of 500 MPa (72,500 psi) and it has a Young's modulus of 210 GPa.

carbonl steels which can successfully undergo heat-treatment have a carbonl 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 carbonl steel, such as stee grade, contains about 0.05% sulfur and melts around 1426–1538 °C (2600–2800 °F)Manganese is often added to improve the hardenability of low carbonl steels. These additions turn the material into a steel">low alloy steel by some definitions, but AISI's definition of carbonl steel allows up to 1.65% manganese by weight.

Hardened steel usually refers to quenched or quenched and tempered steel.

Silver steel or high-carbonl bright steel, gets its name from its appearance, due to the high carbonl content. It is a very-high carbonl steel, or can be thought of as some of the best high-carbonl steel. It is defined under the steel specification standards BS-1407. It is a 1%-carbonl tool steel which can be ground to close tolerances. Usually the range of carbonl is minimum 1.10% but as high as 1.20%. It also contains trace elements of 0.35% Mn (range 0.30–0.40%), 0.40% Cr (range 0.4–0.5%), 0.30% Si (range 0.1–0.3%), and also sometimes sulfur (max 0.035%) and phosphorus (max 0.035%). Silver steel is sometimes used for making straight razors, due to its ability to produce and hold a micro-fine edge, as those made by the French company Thiers-Issard