Billets are semi-finished steel products used to produce long products like bars and structural shapes. They are typically rolled in billet mills, with irregular cross-sections being made using the rolling process. Billets can also be directly cast by a continuous caster, but rolling from ingots is more common. High-speed operation requires cooling of almost every rolling-mill component. The finishing and shipping area is the most space-consuming part and can be a bottleneck in the manufacturing process