HYSD bars possess high yield strength than mild steel but TMT bars yields greater tensile strength, flexibility, and ductility than high yield strength deformed bars. TMT bars or Thermo-mechanically treated bars is a technological progression for the production of high strength deformed steel bars for concrete reinforcement. They have a tougher outer core and softer inner core. The high strength of these bars are obtained from thermomechanical treatment wherein the bars get cooled off intensively right after rolling. The quick reduction in the temperature of the exterior layer makes it harder while the interior layer still being hot. The ductility and strength of the bars enhance due to the tempering that takes place due to the heat from the core of the bar. This approach generates a very strong external surface hardened by the steel crystalline formation. The high temperatures and consequent shaping by twisting and rolling effects in the micro-structure unique to the TMT bars.
Advantages of using TMT bars in construction
Thermomechanically treated bars offer excellent weld-ability, great strength workability, healthier elongation, and ductility. Because of their amazing flexibility in construction and renovation, they are suitable for a broad variety of uses. Using TMT bars in construction increases the speed of construction and decreases the cost spent. TMT bars are lightweight when compared to the other alternatives which make the maintenance and transportation of TMT bars more convenient than others. The thermomechanically treated bars depreciates the risk of damage during earthquake, fire and similar natural disasters. The steel of thermomechanically treated bars rods can be recycled without any lack of quality. The steel frames needed for the production can be easily created and compiled in the construction factory itself.
TMT steel bar doesn’t crack or break even after turning and bending 180 degrees. Better elongation and flexibility of the TMT bars are due to the better ductility of the steel. TMT bars with higher elongation rate are easy to transport and gives better cost efficiency when compared to cold twisted deformed bars. For sounder ‘sudden load absorption’ capability, the Fe 500D TMT bars is preferred because of its ductile nature. TMT bars possess high thermal stability and can withstand temperatures varying from 400 to 600 degrees celsius. Thus, they are excellent for resisting fire and implementing safety.
The thermomechanical process gives the bars anti-corrosive qualities. The water cooling procedure for TMT bars resists the formation of coarse carbides in the bars. Absence of surface stresses and coarse carbides makes the bars corrosion resistant. Using TMT for construction thus aids in the longevity of the structure. When considering TMT bars for construction to ensure quality, it is very important to make sure that its bought from a trustworthy manufacturer.
Grades of TMT bars
There are four distinct grades of TMT Steel available in India; Fe-415, Fe-500, Fe-550, and Fe-600. The grade number, yield strength, and tensility are directly proportional. The higher the grade number, the higher the values are.
Below are the areas of uses for different grades of TMT
- Fe 415: RCC Constructions in areas with great corrosion and earthquake incidence.
- Fe 500: RCC constructions, in building, bridges and other concrete structures.
- Fe 550: RCC construction that is exposed to humid coastal, marine or underground areas.
- Fe 600: used for large RCC construction purposes.