The most important purpose of controlled rolling is to refine grain structure and, thereby, to further improve both the strength and toughness of steel within the as-hot-rol1ed condition. If a survey is constructed of the creation of controlled rolling, it can be seen that controlled rolling contains three stages: (a) deformation inside the recrystallization region at high temperatures; (b) deformation within the non-recrystallization region within a low temperature range above Ar3; and (c) deformation from the austenite-ferrite region.
It is actually stressed that the value of deformation within the nonrecrystallization region is within dividing an austenite grain into several blocks by the roll-out of deformation bands in it. Deformation from the austenite-ferrite region offers a mixed structure made up of equiaxed grains and subgrains after transformation and, thereby, it improves further the strength and toughness.
The fundamental distinction between conventionally hot-rolled and controlled -rolled steels is in the point that the nucleation of ferrite occurs exclusively at austenite grain 34dexppky in the former, while it takes place in the grain interior in addition to at grain boundaries within the latter, ultimately causing a far more refined grain structure. In Stainless Steel Clad Plate a crystallographic texture develops, that causes planar anisotropies in mechanical properties and embrittlement inside the through -thickness direction.
The latter is demonstrated to end up being the main cause of the delamination which appeared inside the fractured Charpy specimens. Fundamental aspects of controlled rolling, like the recrystallization behaviour of austenite, the retardation mechanism of austenite recrystallization because of niobium, microstructural changes accompanying deformation, factors governing strength and toughness, etc., are reviewed. The technique of controlled rolling in plate and strip mills is outlined.