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Hot-Rolled
coil can be processed further using a process known as Cold
Reduction. This processing is carried out for two main reasons.
a)
The need for a scale-free surface for surface-critical applications.
b)
The need for steel to be rolled thinner than is possible in
the Hot Strip Mill.
Cold
reducing the hot-rolled product involves pickling the steel
and then passing it through a number of stands of rolls which
typically reduce the thickness of the steel by about 60-70%.
This produces an extremely hard and unworkable product which
has to be annealed (heat treated) in order to remove the high
stresses and achieve better ductility.
The
annealed coil finally goes through the Temper Mill to ensure
optimum flatness and to achieve the correct surface texture.
Some CR coils are despatched in a dry or un-oiled condition,
but the majority is given a light protective oil coating before
despatch. Another possibility is that the Cold Reduced steel
goes on for further production, to produce metallic-coated
strip products.
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