Cold rolling is a process used in manufacturing and finishing environments to change the thickness, or gauge, of metals or glass. Used mostly in steel mills, cold rolling involves threading flattened steel into a machine that advances the material through a set of rolls. These rolls rotate in opposite directions at a consistent rate of speed, and they are set apart so their width is smaller than the width of the steel sheeting passed through. When the steel goes through the cold mill process, it is pressed into a pre-ordered gauge for further finishing. Often, cold rolling operates in a continuous loop, with multiple sets of rolls working the metal until it reaches a desired thickness or shape.
It is probably most common to imagine steel work as a hot process, with sparks flying and bright orange embers burning around metal. Much of what happens with cold rolling, though, complements the hot rolling process, which is a separate step for reducing the size of steel slabs, sheets, and rods. While hot treatments are most effective for manipulating steel mass, cold rolling refines the metal and works to improve the surface condition. Hot rolling makes the steel malleable, while cold rolling makes it more sturdy.
What occurs in this metal-on-metal process helps to tighten and strengthen the properties of the steel itself. While the steel thickness decreases, most of the breakdown or variable patches that take place in heat processing are built up, or annealed, by the cold rolling. A similar process occurs with glass manufacturing, though the properties of glass make it less capable of holding up through multiple processes.
Most steel companies have long buildings to accommodate their mills, or machinery. The rolling process can begin with a conveyor belt at one end and a shearing blade at another end. A coil of steel is threaded through the mill, and an operator sets the desired gauge and length of the piece to be cold-rolled. Achieving the right gauge involves calculating the roll widths, operating speed and needed lubricant rate, while meeting the specifications of the order.
When a strip has completed its cycles through the mill, it is cut and moved to another conveyor system where its weight, gauge and identifying details are recorded. Further processing or shipment to the customer follows. Using the cold rolling process allows for the creation of production-ready steel for manufacture in a multitude of automotive, construction and industrial environments.