The most important intent behind controlled rolling is usually to refine grain structure and, thereby, to enhance the strength and toughness of steel inside the as-hot-rol1ed condition. When a survey is constructed of the creation of controlled rolling, it might be seen that controlled rolling includes three stages: (a) deformation from the recrystallization region at high temperatures; (b) deformation from the non-recrystallization region inside a low temperature range above Ar3; and (c) deformation within the austenite-ferrite region.
It can be stressed that the importance of deformation inside the nonrecrystallization region is at dividing an austenite grain into several blocks by the development of deformation bands within it. 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 essential difference between conventionally hot-rolled and controlled -rolled steels is based on the fact that the nucleation of ferrite occurs exclusively at austenite grain 34dexppky within the former, even though it occurs in the grain interior as well as at grain boundaries within the latter, leading to an even more refined grain structure. In Galvalume Steel Coil a crystallographic texture develops, which causes planar anisotropies in mechanical properties and embrittlement from the through -thickness direction.
The second is proven to end up being the main cause of the delamination which appeared within the fractured Charpy specimens. Fundamental facets of controlled rolling, like 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 technique of controlled rolling in plate and strip mills is outlined.