Tmt Bars

TMT BARS

The process involves converting the shape stock, viz. ingots, billets to the desired finished section in the hot condition by way of passing the material between a pair of grooved rolls and providing suitable drafts at various stages. The whole operation is conducted at a particular temperature range and within a limited time span. The stages of rolling operation are comprised of heating of feed stock to rollable temperature, rolling the feeding stock in different mill stands, cropping the hot bar during the process of rolling between mill stands as applicable and subsequently finishing in form of hot rolled deformed bar in straight length. The hot bar coming out of the last pass is then conveyed through TMT line and collecting in a cool bed after shearing. The bars at almost ambient temperature are sheared to co mm ercial length stored and kept ready for dispatch. In TMT process hot bars are subjected to quenching by means of an intense cooling installation (cooling installation specially designed spray system) . This step hardens the surface layer to marten site while the core structure remains austensite. When the bar is free of water chamber heat flows from core to surface and surface gets tempered to structure called martensite. In the cooling bed due to atmosphere cooling, the hardened zone is tempered by temperature homogenization in the cross section and the austerite core is transferred to ductile- ferrite- pearlite core.



In case of CTD Bars and wire rods the thinner sections of hot bar coming out of the last pass is coiled through a coiler, whereas the thicker sections of CTD bars are collected on a cooling bed. The strength to the CTD bar is given by twisting it on the twisting machines and not by the quenching process as in the case of TMT bars. Sizes are available from 8 mm to 32 mm .