Can someone explain the difference between hot & cold rolled steel & their different properites & uses?
Rolling involves squashing the steel plate between two heavy, controlable, rollers. This reduces the thickness and can be used to cgange the shape (profile) of the metal being rolled. Hot rolling is where the material is heated to make it malleable (steel is heated until it is yellow hot). Heating enables the crystal structure in the metal to become very fine, regular shaped crystals, and they flow under the pressure of the rollers, the stress put into the crystals flattens them, but being hot the crystals dissolve again and reform into their fine structure.. If cooled this leaves a very fine grain and malleable material. Ingots of metal are hot rolled into the the long profiles used in rail lines. Cold rolled involves no external heat. The crystals are deformed by the pressure in the rollers, but can’t reform into fine small crystals due to the lack of heat. These stressed crystals are not malleable, in fact the material becomes harder (work hardened), and may brittle fracture if over
