The main reason for controlled rolling is always to refine grain structure and, thereby, to improve both strength and toughness of steel inside the as-hot-rol1ed condition. If your survey is made from the creation of controlled rolling, it may be seen that controlled rolling contains three stages: (a) deformation inside the recrystallization region at high temperatures; (b) deformation inside the non-recrystallization region in a low temperature range above Ar3; and (c) deformation from the austenite-ferrite region.
It is stressed that the necessity of deformation in the nonrecrystallization region is dividing an austenite grain into several blocks by the development of deformation bands there. Deformation in the austenite-ferrite region gives a mixed structure composed of equiaxed grains and subgrains after transformation and, thereby, it increases further the strength and toughness.
The basic difference between conventionally hot-rolled and controlled -rolled steels depends on the reality that the nucleation of ferrite occurs exclusively at austenite grain 34dexppky inside the former, although it takes place in the grain interior and also at grain boundaries from the latter, resulting in a more refined grain structure. In Stainless Steel Clad Plate a crystallographic texture develops, that causes planar anisotropies in mechanical properties and embrittlement in the through -thickness direction.
The second is shown to function as the main reason for the delamination which appeared inside the fractured Charpy specimens. Fundamental aspects of controlled rolling, for example the recrystallization behaviour of austenite, the retardation mechanism of austenite recrystallization as a result of niobium, microstructural changes accompanying deformation, factors governing strength and toughness, etc., are reviewed. The concept of controlled rolling in plate and strip mills is outlined.