The role of Hot Rolling mills in a Steel plant

The modern process of ‘hot rolling mill’, owes its conception and invention to Henry Cort of Farhem, England, in 1783. It serves its primary purpose in a steel plant, as a re-heater for the intermediate, semi-finished slabs of steel, known as billets, at their re-crystallization (near melting) temperatures. These semi-melted steel billets are then processed further through pressurized rolls, which further shape them into thinner TMT rods. The accuracy of the metrics and standards in a rolling mill, are detrimental to the quality, and the formation of martensic and austenitic layers of its core. Most of the defects in a steel rod, originating from poor rolling, improper heating, irregular thicknesses, surface defects, etc can be avoided with the proper usage of a hot rolling mill.

Here is a brief description to understand the working and maintenance of hot rolling mills used in a steel plant:

       1.  Construction: The hot rolling mills consists of individual units, that serve their respective physical processes of moulding, shaping, heating, compressing, etc. It comprises of re-heating units, de-scaling (cooling) sprays, roughing mill rolls, edging (compressing) moulds, croppers (cutters), and finishing units. These units function in synergy to work upon the semi-molten steel to form the rods of preferred dimensions. The rolling mill essentially contains three-high rolls, ranging from 24 to 32 inches in diameter, and an oxygen gas torch, that cuts the semi-molten steel into bars. The cooling and backup system for these rolls is combined with a network of coilers, motors, gears and process control systems. 

       2.  Operation: The walking beam furnace reheats the beam, with combustion airs reaching above 1000° F. The hot metal then enters the enclosures of descaling units that spray 1500 psi pressurized cold water, to quench the steel. This removes the iron oxide formed on its outer surface. Here, a scale breaker is introduced to reduce the thickness of the slab further, by heavy rolls. They are then processed through vertical rolling stands that further roughen the edges, and maintain uniformity of the product. The molten metal is then casted into moulds, which form the final bars. They are further surface-treated for finishing, and are further processed for packaging.

       3.  Function: The rolling mill converts the re-heated billets into uniform formed TMT Steel bars. The lattice composition these heat-treated, cold-quenched, hot-rolled bars/rods possess is enhanced. These thermo-mechanical processes are ensured, to further enhance the properties of these bars, by improving the ductility, strength, and durability of steel. The rolling mill serves as an intermediate process, to the furnace that melts the steel, and the final casting of rods.

The consistent advancement in the industrial field is supporting the refinement of the technologies, around the globe. This is crucial to improve the quality of products, which are manufactured throughout the industries. Thus, in a steel industry, the flawless operation of the rolling mill is integral in deciding the quality of rods casted.

Agni Steels boasts of an automated Hot Rolling Mill, that minimizes defects, by automated process control systems, eliminating the possibilities of human errors. This ensures the highest quality, for our exceptional TMT steel rods.