Project Report on ROLLING MILL FOR PRODUCING TMT BARS [Eiri-1505]

Under thermo mechanical treatment (TMT) the steel bars are passed through a specially designed water-cooling system where they are kept till the outer surface of the bars becomes colder while the core remains hot. This creates a temperature gradient in the bars. When the bars are taken out of the cooling system, the heat flows from the core to the outer surface, further tempering of the bars, which helps them attain a higher yield strength. The resulting heat-treated structure imparts superior strength and toughness to the bars. The microstructure of the core is a very fine-grained ferrite and pearlite. TMT bars are also known as 'quenched and tempered rebars', because of the quenching and tempering processes involved in making the bars. The production of quality TMT bar depends on three major factors - quality raw materials, a properly designed and automated mill, and a well-designed quenching and tempering technology. All rebars must be purchased based on the properties of yield strength, tensile strength and elongation values. Deciding the percentage of carbon content in steel has been a major challenge for engineers. While a minimum level of carbon content in steel is essential to achieve the required strength, excess carbon  threatens  its weldability. In TMT bars, this problem has been eliminated by restricting the carbon content to 0.2 per cent to attain weldability and ensuring that its strength is not lost. The joints can be welded by ordinary electrodes and no extra precautions are required.