carbon steel

steel whose characteristics are determined by the amount of carbon it contains

Carbon steel is a metal, a combination of two elements, iron and carbon, where other elements are present in quantities too small to affect the properties. With a low carbon content it has the same properties as iron, soft but easily formed. As carbon content rises the metal becomes harder and stronger but less ductile.Typical compositions of carbon are:

Mild steel .10% to .25% (Ex. AISI 1018 steel)

Medium carbon steel .25% to .45% (Ex. AISI 1040 steel)

High carbon steel. .45% to .95%

Very high carbon steel .95% to 2.1%Steel with sufficient carbon compositions can be heat-treated, allowing parts to be fabricated in an easily-formable soft state then made harder for structural applications. Steels are often wrought by Cold workcold-working methods, which is the shaping of metal through deformation at a low equilibrium or metastable temperature.

Metallurgy - Heat-treatment is an important aspect of carbon steel processing and involves the hypoeutectoid reaction between almost pure iron (ferrite alpha phase), Cementite (iron-carbon compound), and Austenite, which is a reorganized Cubic (crystal system) FCC iron structure that exists only at high temperatures. Carbon has a higher degree of solubility in the austenite phase. The rate at which the steel is cooled through this eutectoid reaction affects the rate at which carbon diffuses out of austenite. Cooling through a hypoeutectoid reaction in carbon steels results in a mostly pearlitic arrangement of alternating layers of ferrite and cementite.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 medium carbon contents (up to 0.3%) and is therefore neither extremely brittle nor ductile (Young's modulus = 212 gigapascalGPa). It is also often used where large amounts of steel need to be formed, for example as structural steel. Carbon steels which can successfully undergo heat-treatment have a Carbon content in the range of 0.30% to 1.70% by weight. It should be noted that trace impurities of various other chemical elementelements can have a significant effect on the quality of the resulting steel. Trace amounts of Sulfur in particular make the steel ''red-short''.

Heat treatment -

Annealing: Heating to a high temperature then cooling slowly. Results in a soft and ductile steel with no internal stresses, often necessary for cost-effective forming.

Normalizing: Heating to a high temperature then cooling at a medium rate in a furnace. Results in steel that exhibits a good balance of mechanical properties, by offering high strength and a good degree of toughness

Hardening: Heating to high temperature then cooling rapidly in water or brine. Also called quenching. Results in steel that is extremely strong but brittle containing a high degree of internal stresses. Results in formation of Martensite, a form of steel that possesses a super-saturated carbon content in a deformed crystalline structure (BCT - Body-Centered Tetragonal) with a high resistance to deformation but with extremely high internal stresses. The technique requires steel with a carbon content high enough to be hardenable.

Case hardening, Flame hardening and Induction_heatingInduction hardening: Only the exterior of the steel part is heated and quenched, creating a hard, wear resistant skin, but preserving a tough interior. The surface of the steel is heated to high temperature then cooling rapidly through the use of localized heating mechanisms and water cooling. Typical uses are for the shackle of a lock, where the outer layer is hardened to be file resistant, and mechanical gears where hard gear mesh surfaces are needed to maintain a long service life while toughness is required to maintain durability and resistance to catastrophic failure. Case hardening requires a steel with a certain level of carbon to be effective. Low carbon steels may be case hardened only if additional carbon is introduced::*Packing low carbon steel parts with a carbonaceous material and heating for some time diffuses carbon into the outer layers. The parts then respond to heat treatments as above. A heating period of a few hours might form a high-carbon layer about one millimeter thick. :*Carboration may also be accomplished with an acetylene torch set with a fuel rich flame and heating and quenching repeatedly in a carbon rich fluid (oil).

Spheroidizing: Heating to a high temperature (austenitic) then cooling at an extremely slow rate through active temperature control. Results in spherically diffused carbon areas with mostly iron rich compositions, also known as spheroidite, as opposed to elongated bands of pearlite. Results in extreme softness and ductility, often only necessary when a high degree of forming is necessary.

Tempering: Reheating hardened steel to a lower temperature then cooling. Reforms crystal structure for a combination of strength and toughness depending on temperature. Necessary when a high degree of internal stresses are present or after quenching when the material is too brittle to be viable for structural applications. Actual temperatures and times are carefully chosen for each composition.A limitation of plain carbon steel is the very rapid rate of cooling needed to produce hardening. In large pieces it is not possible to cool the inside rapidly enough and so only the surfaces can be hardened. This can be improved with the addition of other elements resulting in alloy steel, but may also require exotic cooling methods such as liquid nitrogen.

See also -

Steel

Heat !treatmentCategory:Steelbg: 42;ъгле ;родн& #1072;? !стом&# 1072;наja:炭 素鋼pl:Stal? węglowasl:Ogljikovo jeklo

Battle ready swords, edged weapons, armor and accessories
Manufacturers of high quality edged weapons, armor, chain mail and leather accessories. Suppliers of ceremonial swords and sabers to the armed forces of the World.
http://www.windlass.com/

Custom fasteners and standoffs by Clinch Fast Inc.
Equivalent self clinching fasteners and standoffs. Custom manufactured per customer requirements.
http://www.clinchfast.com/

Electro Polish Systems, Inc.
Worldwide supplier of Electropolishing solutions.
http://www.ep-systems.com/

Amazon.com
Departments include books, music, videos, home and garden, electronics, and toys.
http://www.amazon.com/

BHP Billiton Limited
Mines copper, iron, gold, and coal, and has proved oil reserves. Features investor, news, and customer centres, a section on sustainable development, and information on staff and employment. ( NYSE: BHP )
http://www.bhpbilliton.com/

Specialty Steel and Forge, Inc.
Specialty Steel and Forge is a US supplier of Open Die Forgings and Seamless Rings and Seamless contoured Rolled Rings.
http://www.steelforge.com