Steel is an alloy comprised mainly of iron and carbon. It has good strength which makes it suitable for use in several purposes including infrastructure, building, automobile, ships, trains, weapons, and appliances. The varying amount of carbon in steel impacts the characteristics of the steel including its hardness, strength, and annealing. Steel is manufactured through either of the two processes; blast furnace basic oxygen or electric furnace.
Steel has several types and grades each having its unique properties and characteristics. Steel is a recyclable alloy and most of the steel produced is by recycling old steel. The magnetic properties allow it to be recycled easily and these properties are not affected or change even if the steel is recycled countless times. It requires lower energy to produce it as compared to other alloys.
Steel is used in different forms including flat bar, angles, channel, beam, etc. which are used for several different applications such as engineering purposes, building construction, automobile parts, electrical equipment, surgical and medical equipment, and many other applications.
Steel is classified into two types according to the process used to make it
Both the types of steel are described below in detail along with their differences.
Hot Rolled Steel
Hot rolled steel is a mill process. This process involves heating steel above its recrystallization level. When it is heated at that temperature it can be easily molded and formed. It is considered ideal for manufacturing things that do not require tight tolerances. A large piece of metal is heated and flattened to form a roll. Keeping it at a high temperature it is passed through the rollers at a fast speed. For producing different shapes, it is then divided into sections, and in the case of producing a sheet, it is transformed into coils. It has a tendency to shrink slightly when it cools down. Its scales can be removed either by sandblasting, grinding, or acid bath. For clean and smoother surface brush finishing or mirror finishing can be applied.
It is not recommended for precision applications or applications that require tight tolerances. It is used for applications such as construction, and railroads, and tracks.
Cold Rolled Steel
The processing of cold-rolled steel is carried at room temperature or near about. Cold Rolled Steel is actually hot rolled steel that is processed further after being cooled at room temperature and then annealed, tempered, or shaped. This type of steel has greater strength and hardness because of the lower temperatures. Cold Rolled Steel has usually limited shapes such as flat, square, and round, in order to make other shapes further processing may be required including breaking down, roughing, semi roughing, finishing, or semi-finishing.
The cold-rolled steel is usually used for precise and aesthetic applications due to its smooth gray finishing texture. It is quite expensive due to the additional processing involved to produce it. It is not used for many applications due to its cost, however, most commonly used in applications such as furniture, cabinet frames, tubes, and pipes, home appliances, shelves, strips, rods, bars, ceilings and roofs, walls, aerospace etc.
Cold rolled steel is ideal for products that require exact dimensions, closer tolerances, and a smooth surface finish. It is harder and has greater strength as compared to hot-rolled steel.
Difference between Hot Rolled and Cold Rolled Steel
Hot Rolled Steel
Cold Rolled Steel
Average strength and hardness
Good strength and hardness
Does not have tighter tolerances
It has tighter tolerances
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