The key intent behind controlled rolling is to refine grain structure and, thereby, to improve both strength and toughness of steel from the as-hot-rol1ed condition. If a survey is made from the introduction of controlled rolling, it might be seen that controlled rolling includes three stages: (a) deformation within the recrystallization region at high temperatures; (b) deformation within the non-recrystallization region in just a low temperature range above Ar3; and (c) deformation from the austenite-ferrite region.
It really is stressed that the value of deformation from the nonrecrystallization region is at dividing an austenite grain into several blocks by the roll-out of deformation bands in it. Deformation from 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 essential distinction between conventionally hot-rolled and controlled -rolled steels lies in the reality that the nucleation of ferrite occurs exclusively at austenite grain 34dexppky inside the former, though it occurs in the grain interior along with at grain boundaries in the latter, ultimately causing an even more refined grain structure. In Cold Rolled Steel Coil a crystallographic texture develops, which then causes planar anisotropies in mechanical properties and embrittlement from the through -thickness direction.
The second is demonstrated to function as the main source of the delamination which appeared in the fractured Charpy specimens. Fundamental areas of controlled rolling, including the recrystallization behaviour of austenite, the retardation mechanism of austenite recrystallization on account of niobium, microstructural changes accompanying deformation, factors governing strength and toughness, etc., are reviewed. The practice of controlled rolling in plate and strip mills is outlined.