Rolling process. In rolling the workpiece is drawn by friction through regulated opening of two rotating cylindrical rolls and reduction in the thickness is obtained. The two cylindrical rollers are supported on bearings and are driven by a powerful motor. The opening between the rolls can be adjusted as required. Thus gap is normally referred to as roll gap or regulated opening.
In rolling process. The workpiece is subjected to compressive forces and is deformed plastically. The cross section decreases and length gets elongated whereas the total volume remains same. It is the main metal working process and offers itself to mass production. Close control of the final product is possible.
Rotating rolls will squeeze the workpiece inducing direct compressive stress in it. Friction dominates the process. Rolling of workpiece can be carried out in hot or cold condition. Components produced through rolling have higher mechanical properties than cast products. Slabs, sheets, bars, rods, structural components like I, U, and L, sections, etc., in long lengths can be produced easily.
Steps in rolling process. The starting raw material in rolling is the ingot which is obtained by using a metal die. It will have a certain thickness and length and may have any geometrical cross section.
Ingot can be prepared by melting metal in a furnace and pouring clean well-prepared molten metal with correct temperature into a metal die cavity and allow it to cool. Then take out the solid metal. This solid metal is referred to as ingot or ingot casting. The ingot is then passed through the rolls to get the next set of products.
Classification of rolling process. Rolling process can be classified either. 1. Based on the temperature of the metal during rolling, or 2. Based on the arrangement of the rolls and their number or 3. Based on the products rolled.
Let's see each type. First based on the temperature. The rolling can be classified as hot rolling or cold rolling.
Hot rolling is carried out above recrystallization temperature of the metal and cold rolling is carried out below recrystallization temperature of the metal. In hot rolling, ingot is converted to slab bloom and billet. Then slab is converted to plates, sheet and strip.
Bloom can be converted to channels, rails, beams, and, Pillet can be converted into rod and bar. It is used for heavy or thick sections. In hot rolling the surface finish will be poor but the mechanical properties will be uniform.
In cold rolling is used for converting small sections such as plates, to sheets, and, sheets to foils or, bars, to wires. In cold rolling good surface finishes are obtained with enhanced properties. Second based on roll arrangement.
The minimum number of rolls required for rolling to take place is 2, and, the higher end is dictated by the amount of reduction required, type of metal being rolled, configuration of the product etc. The rolls are cylindrical shaped. The arrangement of rolls could be. 2 high roll mill.
2 rolls are used here. 3 high roll mill. 3 rolls are used here. 4 high roll mill.
Four roles are used here. Cluster role mill. A number of roles are used in conjunction. Planetary role mill.
Roles are arrangement in the form of planetary movement. Tandem role mill. Continuous arrangement of roles are used for continuous rolling.
Sendisma role mill. Similar to a cluster mill but large number of roles are used. Greatest reduction in the material is obtained. Hope you've understood rolling process.
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