Hot Mill Rolling

Hot Mill Rolling – Fabricating the Steel

Rolling is essentially a fabrication process for metals, plastic, paper, glass etc. wherein the material is passed in between a set or series of rolls. There are 2 types of rolling – flat and profile. Flat rolling is where the output is in the form of sheets with a typical thickness under 3 mm. large sheets of paper or metal are made using this kind of process. The other is profile rolling where the output in either in the form of sheets with over 3 mm of thickness, or products like round bars, wires etc. There are 2 kinds of rolling depending upon the temperatures that they operate and run on. These are called hot and cold rolling. The metal is exposed to temperatures higher or lower than its re-crystallization temperature to attain perfect rolling. Thus a hot rolling is where the metal temperature is more than its re-crystallization temperature.

A hot rolling mill is a factory having a series of machinery for shaping metals. Metal in the form of slabs or millets are inducted into a furnace. It is then heated at temperatures above its re-crystallization temperature. Heating them above their re-crystallization temperature causes the metal to deform. The deformed metal is then run in between rollers to form thinner cross sections. These are further run through a set of machinery which gives the desired thickness to the metal.

At the furnace even if the metal is exposed to temperatures higher to its re-crystallization temperature it does not alter any physical or structural properties of the metal. Its micro-structural properties remain unaffected. For making sheets out of metal or cross sections out of millets, hot rolling of the metal is the suggested process. So the main focus of hot rolling is not to alter structural properties of the metal but to rework just on its physical properties by manipulating its shape.

You will come across hot rolling mills in the metallurgical industry, especially with metals like Aluminum and steel. Hot rolling is the initial stage of fine processing of metals. The basic processing of shape happens with hot rolling and the metal in its sheet or rod form is further sent to cold rolling mills for altering into more precise forms.

An interesting example to get the exact picture of fabricating metal into fine and thin sheets would be to consider the case below of the process of making aluminum foil from aluminum metal. The thickness of an aluminum ingot is about 45 cm. prior to it being treated to hot rolling. After running through a hot roll mill it’s compressed in thickness to 5 cm. That’s almost 15 times less its original size. Later sent through a cold rolling process and fine tuning it over and over again it attains its final thickness of about 0.2 mm. which is the thickness of an aluminum foil.

Designing and erection of hot rolling mills is a specialized engineering feat and involves multiple areas of engineering and construction. The various machineries that go into making a hot rolling mill is furnace, temperature maintaining controls and sensors, production and fabrication line. Sheet rolling and packaging are some of the very basic necessaries. Besides these on the erection side there are areas like lay out planning, design, manufacture & supply of equipment, civil and mechanical construction that together lead to creating a fully functional hot rolling mill facility.