Friday, January 2, 2015

TMT Bars

                                                                    TMT BARS

 Thermomechanical processing, also known as thermo-mechanical treatment (TMT), is a metallurgical process that integrates work hardening and heat-treatment into a single process.[1] A description of its application in rebar steel follows.
The quenching process produces a high strength bar from inexpensive low carbon steel. The process quenches the surface layer of the bar, which pressurizes and deforms the crystal structure of intermediate layers, and simultaneously begins to temper the quenched layers using the heat from the bar's core.
     Steel billets 125mm² ("pencil ingots") are heated to approximately 1100°C in a reheat furnace. Then, they are progressively rolled to reduce the billets to the final size and shape of reinforcing bar. After the last rolling stand, the billet moves through a quench box. The quenching converts the billet's surface layer to martensite, and causes it to shrink. The shrinkage pressurizes the core, helping to form the correct crystal structures. The core remains hot, and austenitic. A microprocessor controls the water flow to the quench box, to manage the temperature difference through the cross-section of the bars. The correct temperature difference assures that all processes occur, and bars have the necessary mechanical properties.
      The bar leaves the quench box with a temperature gradient through its cross section. As the bar cools, heat flows from the bar's centre to its surface so that the bar's heat and pressure correctly tempers an intermediate ring of martensite andbainite.
Finally, the slow cooling after quenching automatically tempers the austenitic core to ferrite and pearlite on the cooling bed.

     These bars therefore exhibit a variation in microstructure in their cross section, having strong, tough, tempered martensite in the surface layer of the bar, an intermediate layer of martensite and bainite, and a refined, tough and ductile ferrite and pearlite core.
When the cut ends of TMT bars are etched in Nital (a mixture of nitric acid and methanol), three distinct rings appear: 1. A tempered outer ring of martensite, 2. A semi-tempered middle ring of martensite and bainite, and 3. a mild circular core of bainite, ferrite and pearlite. This is the desired micro structure for quality construction rebar.
     In contrast, lower grades of rebar are twisted when cold, work hardening them to increase their strength. However, after thermo mechanical treatment (TMT), bars do not need more work hardening. As there is no twisting during TMT, no torsional stress occurs, and so torsional stress cannot form surface defects in TMT bars. Therefore TMT bars resist corrosion better than cold, twisted and deformed (CTD) bars.


  1. Nice to read this blog. Really informative. TMT rebars are high strength reinforcement bars. It will add strengthen to your building.

  2. Hi, it was very informative post.Thank you for sharing with us. I think nowadays middle-east companies like alboom groups helping customers to procure all necessary equipment’s and materials for construction projects with the most competitive and reliable materials in terms of cost and quality.
    Carbon Steel Suppliers in Bahrain | Carbon Steel Companies in Bahrain

  3. Excellent blog shared. If anyone looking for steel fibres for concrete then you can contact Precision Drawell. Thanks for sharing.

  4. This is really a nice informative blog, thanks for sharing this and keep sharing with us.
    Wall Painting Service in india

  5. I am very happy to visit your site and i did like it. I was able to get some informative topics.Thanks fo share
    building materials supplier

  6. Thanks for sharing about "Rock Breaking Information online".
    Expando expanding mortar, is a non explosive, non toxic demolition agent, is distributed in Australia and it has wide range of applications.
    Rock & Concret Breaking