In metallurgical engineering, rolling, also known as rolling or calendering, refers to the process of passing a metal ingot through a pair of rollers and rolling it to give it a shape. If the temperature of the metal exceeds its recrystallization temperature during rolling, the process is called "hot rolling", otherwise it is called "cold rolling". Calendering is the most commonly used method in metal processing.
Modern rolling began at Henry Cort's Funtley Iron Works near Fareham, England. In 1783, Henry Cort patented his fluted roll for rolling iron bars. This new design allows the mill to produce 15 times more output than a conventional hammer. Although Hnery Cort was not the first person to use grooved rolls, he was the first to combine smelting steel with rolling forming, so people call him the father of modern rolling.
Extended information:
Hot rolling
Hot rolling is a metal processing process that occurs above the recrystallization temperature of the material. During processing, after grain deformation, the grains recrystallize, which maintains an equiaxed microstructure and prevents cold work hardening of the metal. The starting materials are usually large pieces of metal such as semi-finished castings, slabs, billets and billets. If the raw material comes from continuous casting, the raw material is usually fed directly to the rolling mill at the appropriate temperature. For smaller production scales, the raw materials start at room temperature and must be heated.
Large workpieces are heated in a soaking furnace fueled by oil, gas or natural gas, while smaller workpieces are heated in an electric induction furnace. As the raw material is heated in the furnace, its temperature must be monitored to ensure that the material temperature is above the recrystallization temperature of the metal material. In order to ensure a certain safety factor, the raw material heating temperature must be above the recrystallization temperature; this temperature value is generally 50°C to 100°C higher than the recrystallization temperature.
Hot-rolled metals generally have little directionality in their mechanical properties and residual stresses caused by deformation. However, in some cases, non-metallic inclusions can impart some directionality, and workpieces less than 20 mm thick usually have some directionality. In addition, non-uniform cooling can cause substantial residual stresses, often found in shapes with non-uniform cross-sections, such as I-beams. There is oxide scale on the surface of rolled products, which is an oxide formed at high temperature. Scale is usually removed by pickling or surface cleaning surface processes. [10] The dimensional tolerance of the final rolled product is usually 2 to 5 of the overall dimensions.
Compared to cold-rolled steel, hot-rolled low-carbon steel seems to have a wider range of carbon content, making it more difficult for blacksmiths to control the quality of the finished product. Also for similar metals, the cost of hot-rolled products is generally lower than that of cold-rolled products.
Hot rolling is mainly used to produce sheet metal parts or products with simple cross-sections, such as rail tracks. Other typical uses for hot rolled metal include truck frames, automotive wheels, pipe and tubing, water heaters, farm equipment, belts, stampings, compressor casings, rolling stock components, wheel rims, architectural metal structures, railroad hopper cars, doors , shelves, CDs, guardrails, car clutch plates.
Baidu Encyclopedia-Rolling