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In metalworking, rolling is a metal forming process in which a metal billet is passed through one or more pairs of rolls to reduce thickness,uniformize thickness,and/or impart desired mechanical properties.The concept is similar to rolling dough.Rolling is classified by the temperature at which the metal is rolled.If the temperature of the metal is above its recrystallization temperature,the process is called hot rolling.If the temperature of the metal is below its recrystallization temperature,the process is called cold rolling.In terms of volume used,the hot rolling process has a larger tonnage than any other manufacturing process,while the cold rolling process has the largest tonnage of all cold working processes.Mill stands containing pairs of rolls are grouped together into rolling mills that rapidly process metal (usually steel) into structural steel (I-beams, angles,channels),bars,and products such as rails. Most steel mills have a rolling mill department that converts semi-finished castings into finished products.
Iron and steel
The invention of the European rolling mill may be attributed to a painting by Leonardo da Vinci.The earliest rough rolling mills were found in the Middle East and South Asia as early as 600 BC,but the basic principle is the same.The earliest rolling mill was the slitting mill, which was brought to England in 1590 from what is now Belgium.These rolling mills pass flat steel between rolls to form iron plate, which is then passed through grooved rolls (slitters) to produce iron bars.The first experiments with rolling tinplate were carried out around 1670.In 1697,Major John Hanbury established a factory at Pontypool to roll "Pontypool plates"-black steel plates.It was later re-rolled and tinned to make tinplate.Early plate iron production in Europe took place in forges,not rolling mills.Slitting machines suitable for the production of hoops (for barrels) and iron of semicircular or other cross-section,which were the subject of two patents from c. 1679.Some of the earliest references to rolling mills date back to Swedish engineer Christopher Polhem in his Patriotista Testamente of 1761, in which he mentions rolling mills for plate and bar iron.He also explains how the rolling mill saves time and labor because it can produce 10 to 20 or more bars simultaneously.In 1759,Thomas Blockley of England patented metal polishing and rolling.In 1766, Richard Ford of England received another patent for the first continuous rolling mill.A tandem mill is a rolling mill that rolls metal in continuous stands;Ford's tandem mill is used for hot rolling wire rod.
Until the 18th century, rolling mills were powered by water wheels.The first recorded use of a steam engine directly driving a rolling mill is attributed to John Wilkinson's Bradley Works,1786, when a Boulton and Watt engine was connected to a slitting mill.The use of the steam engine greatly increased the production capacity of factories until this form of power was replaced by electric motors shortly after 1900.Modern rolling practice can be attributed to the pioneering efforts of Henry Cort of Funtley Iron Mills near Fareham, Hampshire, UK.In 1783,Henry Cort received a patent for rolling iron bars using grooved rolls.With this new design,the mill could produce 15 times more per day than with a hammer.Although Cort was not the first to use grooved rolls, he was the first to combine many of the best properties of the various ironmaking and forming processes known at the time.Therefore,modern writers call him "the father of modern rolling".The first rail rolling mill was established by John Birkenshaw in 1820 at Birlington Iron Works in Northumberland,England,where he produced fish maw shaped wrought iron rails 15 to 18 feet in length.With the advancement of rolling mill technology,the scale of rolling mills increases rapidly with the size of rolled products.An example of this is at the Great Exhibition in London in 1851, where the Consett Iron Company exhibited a plank 20 feet long,3 1⁄2 feet wide,7/16 inch thick and weighing 1,125 lbs.The rolling mill developed further with the introduction of the three-high rolling mill in 1853 for rolling heavy sections.