A rolling mill is used to straighten and/or change the thickness of sheet metal, slabs, or ingots. Rolling mills can also be used to add texture and shape to metals depending on the need and the rollers that are installed in the machines.
Types of Rolling possible with rolling mills
Hot rolling mills roll the steel at temperatures over 1700° F which is above the steels recrystallization temperature meaning that it can be shaped and formed more easily and the steel can be rolled in much larger sizes. Hot rolled steel products will shrink slightly after they cool and are therefore harder to control in terms of size. Hot rolling machines have the problem of scale building up on the exterior of the metal meaning that hot rolling machines must be combined with other devices such as high pressure water descalers to remove scale from the metal multiple times during the rolling process. Hot rolled steel is used in a variety of industries including railroads where tracks and I beams are made from hot rolled steel. Hot rolled coils of metal are also used to feed into cold rolling machines. Hot rolling mills require different rollers and materials in the machine to make sure that it can handle the stress added by the temperature of the metal.
Cold rolling mills roll the steel at temperatures below the recrystallization point of the metal (usually room temperature). Cold rolled steel demands almost twice as much money compared to hot rolled steel. Cold rolling is a more complex process where the metal’s yield strength and hardness increase compared to the hot rolling process. Cold rolling is normally used to decrease the thickness of steel. Cold rolling is more precise than a hot rolled product. However, cold rolled steel is limited to round, square, flat and other such variations due to the inferior malleability compared to the hot rolling process. Most cold roll steel is formed from steel made from a hot rolling process.
Rolling Mills for Jewelers
Smaller rolling mills are also used by jewelers to decrease the thickness of metal before it is made into jewelry. These machines may also be used to impress patterns on the metal or to make it into specific shapes depending on the shape of the rollers installed in the machines.