Rolling (metalworking)

{

"text": "Rolling is a fundamental metalworking process used to shape metal stock.

In this process, metal is passed through one or more pairs of heavy rolls. The pressure from these rolls reduces the thickness of the metal. It can also make the thickness uniform across the entire piece. Beyond just changing the shape, rolling can change the mechanical properties of the metal. This means it can make the metal stronger or more flexible.

\n\nThe mechanism of rolling depends heavily on the temperature of the metal. Rolling is classified into two main types: hot rolling and cold rolling. Hot rolling occurs when the metal is heated above its recrystallization temperature. At this temperature, the internal grains of the metal deform and then recrystallize. This process prevents the metal from work hardening, which is when metal becomes brittle as it is shaped.

Cold rolling happens when the metal is processed below its recrystallization temperature. This is usually done at room temperature. Cold rolling increases the strength of the metal through a process called strain hardening. This can increase the strength by up to 20%.

\n\nHot rolling is used to produce large, simple shapes like sheet metal or rail tracks. The starting material for hot rolling is often large pieces called ingots, slabs, blooms, or billets. If these are not already at the right temperature from continuous casting, they must be heated. Larger workpieces are heated in gas- or oil-fired soaking pits. Smaller pieces might use induction heating.

Because the metal is so hot, a surface layer called mill scale forms. This oxide layer is often removed later through a process called pickling. Cold rolling is used for smaller, more precise products like sheets, strips, bars, and rods. It provides a better surface finish and tighter dimensional tolerances. Some cold rolling, called skin-rolling, involves very little reduction. It only reduces thickness by 0.5% to 1% to create a smooth surface.

\n\nHistory shows how rolling technology has evolved over centuries. The earliest rolling mills were slitting mills, which arrived in England from Belgium in 1590. These mills passed flat bars through rolls to create iron plates. Later, these plates were passed through grooved rolls called slitters to make iron rods.

In 1783, Henry Cort received a patent for using grooved rolls for iron bars. Cort is often called the \"father of modern rolling\" because he combined many different ironmaking features. His design allowed mills to produce 15 times more output per day than using a hammer. In 1820, John Birkenshaw established the first rail rolling mill in Northumberland, England. He produced wrought iron rails that were 15 to 18 feet long.\n\nModern rolling mills are highly complex and specialized machines. They are often organized into different sections: roughing, intermediate, and finishing cages.

Some mills are designed as tandem mills, where metal passes through several stands in a series. These are used for precise thickness control in strip rolling. Other machines are continuous mills, which process metal without interruption to ensure high production rates. Universal mills are even more advanced, using both horizontal and vertical rolls. This allows them to create shapes like H-beams and wide plates with high accuracy.

These specialized rolling mills can be very expensive, sometimes costing up to 2 million euros.\n\nThere are many specific types of rolling processes used in industry today. Ring rolling is one method used to shape metal into rings.

Roll bending is used to create cylindrical products from metal plates.

Roll forming is another technique used to shape metal. Profile rolling is used to create specific shapes, and controlled rolling allows for precise management of the metal's properties. Engineers even use Artificial Intelligence and numerical models to design the best way to roll a bar. This helps them reduce the number of \"passes," or times the metal goes through the rolls, which saves time and money.\n\nRolling is a vital part of the global manufacturing system. It is the process that converts semi-finished casting products into the finished goods we use every day. Most steel mills have dedicated rolling mill divisions for this purpose. This industry produces essential items like structural steel, including I-beams, angle stock, and channel stock. It also produces the rails used for transportation and the bars used in construction. Without the efficiency of modern rolling mills, producing the massive amounts of metal required for modern infrastructure would be nearly impossible.",

"media": [

"File:Rolling compressed.gif",

"File:Rolling schematic view",

"File:Soaking pits.png",

"File:The Employment of Women in Britain, 1914-1918 Q28453.jpg",

"File:A coil of hot-rolled steel",

"File:rolling-mill.jpg",

"File:Slitting mill.jpg",

"File:Szelvenyek01.jpg",

"File:Rolling mill configurations.svg",

"File:Ring rolling.png",

"File:Rundwalzen.png"

]

}