What is Hot Rolled Strip Steel? Steel Foundations
Hot rolled coils (HR or HRC) are the flat product that is produced from hot rolling slabs in a hot strip mill.
The hot rolling process begins with either a thick or thin continuous cast slab exiting the reheat furnace at a rolling temperature hot enough to achieve the desired final properties. Due to the extreme amount of reduction done during this process, the slab must be heated above the material’s recrystallization temperature. After reheating, the material is descaled, which is where the iron oxide surface scale is removed with high-pressure water to ensure a clean surface.
The reheated slab then enters the multiple stand roughing mill section to begin reducing the slab’s thickness. Some hot strip mills, called reversing mills, accomplish the roughing step by rolling the slab back and forth through a singular rolling mill stand. As the slab is reduced in thickness, its length increases, and its as-casted microstructure breaks down.
After being hot rolled to roughly its final dimensions, the material is descaled again before entering the finishing section of the hot mill. Using a series of five to seven rolling mill stands working in tandem with each other, the hot rolled coil is rolled to its final thickness.
Next, the hot rolled coil will travel down the runout table and be cooled via water sprays. This cooling zone regulates and develops the steel’s microstructure, grain size, and properties. Finally, the hot rolled material is rolled up into a coil in the down-coiler and banded, packaged, and marked for shipment.
Finished hot rolled strip can either be sold as hot rolled band (HR) or sent to be pickled and oiled (HRPO). Other subsequent processes can include slitting, annealing, heat treating, and cold rolling.