Hot Roll (HR)
The initial step in creating flat roll steel from melt. A steel slab is heated to a formable temperature and run thru a series of rolls to reduce the slab’s thickness to a desired gauge. This process creates a Hot Roll coil as the strip is recoiled after rolling.
Cold Roll (CR)
This process takes a HRPO coil and by forcing it thru a series of rolls, reduces the thickness of the strip and improves the surface. The HRPO coil is not heated prior to this operation and is reduced simply by force. The strip is referred to as Cold Roll Full Hard following cold reduction. It can be utilized in this form, but the majority of CR product is further processed thru annealing and temper rolling. Annealing removes the stresses imparted in the steel during cold reduction and improves ductility. The temper pass improves the cross sectional shape of the strip and imparts the final gauge and physical properties.
Hot Rolled Pickle & Oil (HRPO)
After hot rolling the steel strip has a rough surface covered with scale and oxides. The pickling process involves running the steel strip thru an acid bath which removes the scale and produces a clean, paintable surface. Oil is applied after pickling to prevent rust.
Hot Dip Galvanized (HD Galv)
The strip is run thru a molten zinc bath. The zinc is cooled and solidified on to the strip. The strip is then recoiled. This process results in a material with the strength and formability of steel, with the added corrosion protection of zinc.
Similar to HD Galv, but following the coating process the strip is immediately run thru an annealing furnace and then recoiled. This step anneals the zinc coating to the steel strip. The high heat caused the iron (Fe) in the base metal to combine with zinc(Zn) coating to form a iron/zinc layer. The coating appearance is dark grey.
Electro Galvanized (EG)
Zinc is applied electrolytically to the steel substrate. Zinc particles in a bath are electrically charged and the substrate receives the opposite charge, and opposites attract.
Similar to HD Galv, but the molten bath is comprised of 55% Zinc and 45% aluminum. Galvalume has superior corrosion resistance and is primarily used in metal building applications.
This process applies molten aluminum to the steel strip in a like manner to HD Galv. Aluminized steel is used heat resistant applications, such as automotive exhaust systems.