Steel Hot Rolling, Hot Rolling of Steel, Metal Rolling, Metal Forming Process, Steel Rolling Process, Metalworking, Flat Rolling Fundamentals, Physical Metallurgy, Hot Rolled Steel, Rolling Mills (Pre-Treatment of Hot Metal, Heat Treatments for Hot-Rolled Products, Steelmaking Refractories, Refining of Stainless Steels, Steel Heating for Hot Rolling, Oxygen Steelmaking Processes)

 

In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness and to make the thickness uniform. Rolling is classified according to the temperature of the metal rolled. When the temperature of the metal is above its recrystallization temperature, then the process is known as hot rolling.This makes the steel easier to form, and also results in products that are easier to work with.

Roll stands holding pairs of rolls are grouped together into rolling mills that can quickly process metal, typically steel, into products such as structural steel, bar stock, and rails. Most steel mills have rolling mill divisions that convert the semi-finished casting products into finished products.

Rolling of steel is one of the most important manufacturing processes for steel. It is usually the first step in the processing of steel after it is made and cast either in Ingot or continuous cast product in a steel melting shop. Hot rolling is used mainly to produce sheet metal or simple cross sections, such as rail tracks. Other typical uses for hot rolled metal includes truck frames, automotive wheels, pipe and tubular, water heaters, agriculture equipment, strapping, stamping, compressor shells, rail car components, wheel rims, metal buildings, railroad hopper cars, doors, shelving, discs, guard rails, automotive clutch plates.

Torque and power are the two important component of rolling. Torque is the measure of the force applied to the rolls to produce rotational motion while power is applied to a rolling mill by applying a torque to the rolls and by means of work piece tension. In a rolling mill the power is spent principally in the following four ways.

·         The energy needed to deform the steel.

·         The energy needed to overcome the frictional force.

·         The power lost in the pinions and power transmission system.

·         Electrical losses in the various motors.

Rolling can be done either by hot rolling or by cold rolling. Cold rolling usually follows the hot rolling.

Hot rolled steel typically requires much less processing than cold rolled steel, which makes it a lot less expensive. Hot rolled steel is also allowed to cool at room temperature, so it’s essentially normalized, meaning it’s free from internal stresses that can arise during quenching or work-hardening processes.

For hot working processes, large deformation can be successively repeated, as the metal remains soft and ductile. Themetal stock is subjected to high compressive stresses as a result of the friction between the rolls and themetal surface. Rolling involves passing the material between two rolls revolving more or less at thesame peripheral speed but in opposite directions, i.e., clockwise and counterclockwise. The distancebetween them is spaced, which is somewhat less than the height of the metal stock entering them.These rolls can either be flat or grooved (contoured) for the hot rolling of rods or shapes.

India witnessed a shift towards increased usage of hot rolled (HR) steel at the expense of cold rolled (CR) steel. The slab and strip casting together with the induction of continuous hot rolling has brought about the change. The major advantage of this technology is the low operating cost as it permits the use of non-coking coal. HR products are expected to maintain a high growth profile in the coming years, with export opportunities in India.

 

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