Steel Finishing
Where strip steel is prepared for end-use applications in terms of controlled flatness, surface finish and mechanical properties.
Severstal Warren’s finishing facilities consist of two pickling lines, an acid-regeneration plant, a cold-reduction mill, batch annealing and hydrogen-annealing units, two temper mills, a hot-dip galvanizing line and other finishing units.
The two pickling lines remove scale formed during hot rolling. The coils are unwound and cleaned in a bath of hydrochloric acid solution also known as pickle liquor. Both pickling lines have a combined annual capacity of 865,000 tons.
The pickling lines are connected to the acid regeneration plant, which cleans and recycles waste pickle liquor. The regeneration plant is an example of a cost-effective environmental control.
The pickled coils are reduced to near final gauge on the tandem mill, also known as the cold rolling mill. Severstal Warren’s 54-inch, 4-stand tandem mill rolls steel to make the product thinner and smoother and to give it a higher strength-to-weight ratio.
Severstal Warren’s batch-annealing facility is used to soften steel to make it more formable after the cold-rolling process. Steel coils are stacked on a base and covered. A furnace then is lowered to reheat the steel in an atmosphere of 93 percent N² (nitrogen) and seven percent H² (hydrogen).
Hydrogen annealing is a batch annealing process in an atmosphere of 100-percent H², which further improves the metallurgical properties and overall quality of steel.
The two temper mills roll steel to the customer’s desired flatness, metallurgical properties, surface finish and final gauge. Severstal Warren’s two temper mills have a combined annual capacity of 600,000 tons. One mill, a single stand two-high mill, is used primarily for hot-rolled products and the other, a single-stand four-high mill, is used for cold strip finishing products.
The hot-dip galvanized line is a dry-flux type unit that coats a variety of hot- and cold-rolled base products with a zinc finish for long-lasting corrosion protection. Steel entering the 834-foot line is first cleaned to ensure a uniform coating before it enters the molten-zinc coating bath. After the finish is applied, the strip enters a cooling tower where the coating solidifies. The strip is then flattened and coiled.
Other finishing units include a 48-inch slitter to process galvanized products and a 35.5-inch roll former that converts coils into sheets.