Original Date: 08/26/1996
Revision Date: 01/18/2007
Information : Continuous Annealing Line
Weirton Steel Corporation (WSC) operates three continuous annealing lines to rapidly clean and anneal (soften) cold rolled steel. Through the process of reducing nine-inch-thick steel slabs to thin gauge sheet steel, the metal is work hardened and contaminated with lubricating oil. To soften this material for finish processing, the steel must be cleaned and then annealed to the desired hardness.
The process of continuously annealing cold rolled steel begins by loading two coils of steel at the input of the continuous annealing line. The steel is put through a clean and rinse bath followed by a hot rinse dryer. A vertical accumulator keeps the continuous line running while a changeover is made from coil #1 to coil #2. The steel is run down the line to the various machines in the process line. When coil #1 is expanded, the second coil is welded onto the tail end of the first coil by a continuous lap welder. However, the lines are not interrupted because of the additional length of steel in the accumulator. After these processes are completed, the steel travels through a furnace where it is heated to the required temperature, held at that temperature, cooled, and then cooled in a quench tank. After the quench tank, it is wound, cut and removed to another processing line for further operations.
These continuous annealing lines vary in speed from 1,000 to 1,800 feet per minute. Without these continuous annealing lines, WSC would have to anneal all cold rolled steel in batch furnaces that can only anneal 16 coils of cold rolled steel in 25 to 35 hours. Once started, a continuous annealing line can anneal the same amount of steel in four hours.
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