In the rolling process of steel mill, handling is controlled to create unnecessary initial
strain at the minimum possible.
However, in actual process, there is another system for removing such initial strain,
which is called "Tension leveler" in the case of thin plate.
As the plate thickness becomes thinner, the diameter of rolls became smaller.
In the case of Aluminum alloy, the thinnest thickness is 0.2(mm), and 0.3(mm) for
Copper alloy.
