It is important to note that one of the main differences between hot-rolled and cold-rolled steel is the process. The term "hot rolling" refers to the heating process. "Cold rolling" is a process that takes place at or near room temperature. Although these techniques can affect overall properties and applications, they should not be confused with the formal specifications and grades associated with metallurgical composition and performance grades. The different grades and specifications can be hot-rolled or cold-rolled - including basic carbon steels and other alloy steels.
The raw material of cold rolled steel coil is high quality hot rolled product, and after pickling continuous rolling, degreasing, annealing, skin pass, slitting and cut to length line etc.
Firstly, the hot rolled steel coils are used as raw mateirals, the oxide film was removed with pickling and annealing. During this process, the hardness of the hot rolled coils are lowered, and the performance of steel is improved. There are Two kinds of annealing treatment, one is Bell-type annealing furnace producing bright steel coils, the other is Continuous Annealing furnace producing black steel coils.
Hot-Dipped Galvanized Steel Coil
Hot rolled steel usually requires much less processing than cold rolled steel, which makes it much cheaper. Because hot-rolled steel can be cooled at room temperature, it is essentially normalised - meaning that it has none of the internal stresses that can arise from hardening or work-hardening processes.
Hot-rolled steel is ideal where dimensional tolerances are less important than overall material strength and surface finish is not a critical issue. If surface finish is an issue, scale can be removed by grinding, sandblasting or pickling in an acid bath. Once the scale has been removed, a variety of brush or mirror finishes can also be applied. Descaled steel also provides a better surface for paint and other surface coatings.
Cold-rolled steel has better surface characteristics than hot-rolled steel, so it is not surprising that cold-rolled steel is often used for technically more precise applications or applications where aesthetics are important. However, they are more expensive due to the additional processing of the cold finished product.
This may seem obvious, but certain types of steel are more suitable for certain applications. Knowing which one to use helps to avoid overspending on raw materials. It can also save time and money on additional handling. Understanding the differences between hot and cold steels is essential to choosing one or the other.
Cold Rolled Steel Coils;bsp;
In terms of physical properties, cold-rolled steel is usually harder and stronger than standard hot-rolled steel. As the metal is formed at a lower temperature, the hardness, tensile fracture resistance and deformation resistance of the steel are all increased by work hardening.
However, these additional treatments can also create internal stresses within the material. This can lead to unpredictable warpage if the steel is not stress relieved prior to cutting, grinding or welding.
Depending on what you are building, different materials have their own advantages and disadvantages. For general projects or one-off production, steel materials can provide the building blocks for any conceivable structural configuration.