Hot-rolled steel
Before rolling, the metal is usually already very hot and above the recrystallization temperature of the previous operation. This process eliminates any stress and grain deformation caused by an increase in working temperature. During the cooling process, uneven cooling may occur, leading to residual stress in the product. Hot rolling is mainly used for the production of metal plates or simple cross-sectional products, such as rails and I-beams.
Hot rolling is usually not as expensive as cold rolling or cold drawing because steel has more ductility at higher temperatures. The production of steel also lacks one step, which reduces the operating costs of producing steel. The surface finish of steel is not as smooth or clean as that of cold rolled or drawn steel, and the mechanical properties of steel are usually not as good as that of cold drawn steel. This is usually not important for steel that is produced in large quantities and does not require a clean external finish.
Cold rolled steel
Cold rolling, usually carried out at room temperature, has the additional effect of work hardening and strengthening materials, thereby further improving the mechanical properties of materials. It also improves surface finish and maintains stricter tolerances. However, the ductility of room temperature steel is not as good as that of hot-rolled steel, so cold rolling cannot reduce the thickness of the workpiece like single pass hot rolling. Typical cold rolled products typically include similar hot rolled products, such as plates and bars, but are usually smaller.
Cold drawn steel
Like cold rolling, cold drawing is carried out at room temperature, but it is not the production of flat objects such as coke cans, but the production of steel into metal wires such as wheel spokes or paper clips. To begin this process, steel is usually hammered and rolled for assembly through molds; A tool for turning steel blocks into wire. The room temperature steel is pulled through the mold, which reshapes it into a thinner shape while maintaining the same volume. This is similar to the idea of syrup flowing out of a bottle through a pipe, as it changes shape but does not change volume, but rather is pulled out rather than squeezing metal. In order to achieve the appropriate diameter of the wire, it is usually necessary to pass through different molds multiple times.
Cold drawn steel can come in a variety of shapes and sizes, but it is commonly manufactured as bar or wire. The diameter of steel bars varies, and shapes of the bars are often determined by how you look at them straight on, which may include flat, square, round and hex bar shape. Steel wire is often manufactured to the customer’s specifications, and may come in different types of finishes.
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Post time: Jun-21-2023