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Rolled carbon steel is a metal alloy that has been passed between two rollers to compress the metal into sheets, strips, bars or rods. This metalworking process can be applied to hot or cold metal. Hot rolling process the metal while it is at a temperature that is high enough for the metal to deform and recrystallize, while cold rolling processes the metal while it is at room temperature.
Carbon steel is a metal alloy that is a mixture of iron mined from the earth and carbon. Although carbon steel is not the only metal alloy that is based on iron, it is the one that is most frequently used in manufacturing. To transform carbon steel stock into a form that can be used to construct other products, steel mills can use a type of metalworking called rolling.
Rolling passes the metal through the middle of a pair of revolving cylinders. The pressure from the rollers squeezes the carbon steel stock into more manageable forms, such as flat sheets, strips, bars or rods. Processing the carbon steel stock in this way makes it easier to divide, transport, store and use for its intended purpose.
Steel mills can process rolled carbon steel by hot-rolling or cold-rolling the steel. These labels give a clear indication of the distinction between the two types of rolling. Hot-rolling puts the carbon steel stock through the rollers while the metal is hot and malleable, while cold-rolling puts the carbon steel through the rollers while it is at room temperature or at any temperature that is below the metal's recrystallization point.
The important distinction between the two processes is in the hardness of the steel that results. Recrystallization prevents the steel from strain hardening, so hot rolled carbon steel is not as hard or brittle as steel that is cold rolled. Processing the metal stock while it is hot results in a product that is more flexible, or ductile, and has more tensile strength. Hot rolled carbon steel is most often formed into metal sheets and used to build load-bearing structures that need steel that has some flexibility.
Cold rolled carbon steel is used for a variety of consumer-related purposes. The steel is less ductile, and since it is not subjected to heat that can distort measurements until the product cools, cold steel can be precisely measured before it is processed through the rollers. This type of rolled carbon steel tends to be more expensive and is used to build products such as cars, planes and home appliances.