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Cold Rolled Steel Strips

Cold rolled spring steel strips or cold rolled close annealed steel coils are made from Hot Rolled Coils / Skelps / Sheets. Cold Rolling is a process through which the Hot Rolled steel sheet or strip after Pickling process is introduced between rollers by application of high pressure at temperature below the re-crystallization temperature. This method basically imparts smooth surface finish, accurate thickness, high tensile strength, yield strength hardness with corresponding decrease inductility. Hence selection of proper combination of steel composition, degree of cold working and heat treatment play a pivotal role to produce cold rolled sheets / strips having diverse applications and mechanical properties suitable for a wide spectrum of end users including segments like Automobiles, Bicycles, Trains, Washing Machines, Compressors for ACs and Refrigerators, Cutting Tools like Saws and Blades, and a host of other sheet metal components.

Cold Rolling Process

Cold Rolling involves production of permanent deformation of steel strip for any given pass by exceeding the elastic limit of the steel strip as a result of load in general, is determined by the mill design, power, steel strip's width, total amount of reduction, lubrication, hardness of the spring steel strip , steel surface, steel tension, roll diameter and roll surface. However the lowest percentage reduction in the last reduction pass to permit better control of flatness, gage and finish of the product. The modern Rolling Mills i.e Tandem Mills are equipped with hydraulic automatic guage control system, hydraulic work roll bending system for controlling strip shape / profile of the coil, high crown 6 high roll shifting system quick roll changing, on line shape meters to monitor and control the strip flatness and guage display system, micro processor control operation in auto mode, agitation and filtration system for supplying emulsion to the rolls along with detergent strip cleaning in the last finishing stand. Also, development include adjustment of roll gap profile by intermediate rolls featuring continuous variable crown and enhanced shifting strategy for equalization of roll contact loads to result in lower roll wear coupled with design of work rolls as EDC rolls for reduction of the edge drop effect.

The cold rolled strip / coil after exiting the reversing / tandem mill is extremely hard and stiff exhibiting greater amounts of spring back when bent and have very limited applications. This necessitates the sheet / strip to be annealed for softening it and make it useful. The steel strips / coils that are produced during this cold rolling process can be cold rolled low carbon steel strips / coils or cold rolled medium carbon steel strips / coils or cold rolled high carbon steel strips / coils.