Black Round Bar

Black Round  bars are created by the 'rolling process' in which the steel is passed over many rolls while heating raw materials like blooms, billets, etc. at temperatures of approximately 1200 C (approx. 2100 F) which is more than the steel's recrystallization temperature of around 1200 C (approximately 2100 F. In this temperature range steel can be bent into any desired shape and is able to be produced in large dimensions. Black bars are formed without two reheating passes to ensure accuracy so they're usually created without any delay during the process. This process doesn't give exact control over the shape and size of the bar because it is able to shrink slightly upon cooling. This is the reason black bars are more expensive than bright bars.

The use of black steel is in cases where exact forms and tolerances aren't needed, for instance in building trades and welding for the making of railroad tracks as well as I-beams. As as compared to the dark bars, bright bars are less suited to use and also tend to be more expensive in price.