Total annual capacity of the Severstal Columbus continuous, three-stage hydrochloric acid pickle line is close
to 1.2 million tons, consisting of approximately 360,000 tons of hot rolled pickled and oiled and the balance
fed to the directly coupled 5-stand tandem cold mill complex.
The existing complex can produce cold rolled strip, 0.0124–0.075 inch thick, 36–72 inches wide, and hot rolled pickled and oiled, 0.055–0.191 inch thick, 36–74 inches wide, in coil weights up to 88,000 pounds. The complex is housed in a 556,000 sq. ft. building consisting of three finishing bays.
Maximum process section speeds are:
- Entry to pickle line: 1,476 feet/minute (450 m/minute).
- Process: 492 feet/minute (150 m/minute).
- Exit from tandem mill: 4,100 feet/minute (1,250 m/minute).
Hot band coils are delivered to the pickle line walking beam conveyor by a shuttle car and uncoiled on a single 30-inch expandable mandrel payoff reel. Strip then proceeds through a flattener, crop shear and flash butt welder into a horizontal entry, tension regulated accumulator. The accumulator is a 6-strand unit, with one looper car that can operate at 1,600 feet/minute and has a storage capacity of 1,673 feet.
Strip leaving the entry accumulator passes through a tension-leveling scalebreaker that can provide up to 3% elongation. The strip then passes through three shallow bath, turbulent-type, 59-foot-long pickle tanks. The tanks are granite-lined with water-sealed plastic hoods, and can be drained and restarted without removing and rethreading strip in the line. Strip pickling uses an 18% regenerated hydrochloric acid; spent pickle liquor is trucked from the site for disposal.
Following the pickle tanks are a 5-unit cascade rinse section, a dryer and a 2-strand intermediate strip accumulator with a storage capacity of 656 feet. Strip then passes through a turret-head slitter and inspection station that permits both vertical and horizontal visual examination, then into a 6-stand delivery accumulator with a storage capacity of 984 feet.
Depending on whether the strip is destined to be cold rolled or produced as hot rolled pickled and oiled, the material is delivered directly to the 5-stand tandem cold mill or to an exit section with an electrostatic oiler, coiler and conveyor that delivers coils to a crane. The pickle line operation is supported by a laboratory that is used to monitor the pickle acid HCl and Fe levels, as well as checking the final rinse water for the presence of chlorides.
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