TMT Steel Bar – Manufacturing & Construction Basics
TMT steel bar is a steel reinforcement type that comes up with the required strength in tension, bending, shear and compression. TMT steel bar is defined as Thermo Mechanically Treated Steel that offers better ductility and malleability.
Generally, there are four types of reinforcement steels have been used in the construction – mild steel bars, deformed bars, cold twisted bars and TMT bars. Among them, TMT bars are considered to be high-quality steel bars that meet the construction requirements in terms of getting standard toughness and strength.
To understand the TMT steel bar better, you need to know the other three steel types and their application.
Mild steel bar: With a low tensile strength, mild steel bars are easy to produce and are used in allowing and manufacturing of a steel structure fabrication used in the construction work. They have low carbon and silicon level and have come up with less tensile strength than others. Their surface is plain and the round part comes up with diameter from 6 to 50mm. They can be bent easily that allows the workers to cut the rod in pieces without damage.
Deformed bars: Deformed steel bar has come up with normal ductility and has applications in residential, commercial and infrastructure fields. The common size of such steel bar stays in between 9m to 12m. The diameter of this bar varies according to their weight. The surface of the bar has lugs, ribs or deformation that provide better grip to concrete and maintains a strong bond between the two components.
Cold Twisted bars: Cold twisted bars are manufactured through a cold twisting process where bars are hardened and twisted when they stay cold. But twisting can cause surface defects on steel bars because of the occurrence torsional stress in the rebar. Torsional stress is generated by an applied torque during the twisting of an object.
TMT Bar – the basics: TMT bar goes through a metallurgical process that uses mechanical or plastic deformation process and a thermal process together. TMT stands for Thermo Mechanical Treated – the way these bars are manufactured. Mechanical deformation process includes compression or rolling, and thermal process covers heat-treatment, water quenching and cooling in a single course.
To produce TMT bars, the hot rolling process comes first that makes heated iron billets pass through the rollers of decreasing diameter. After completing the hot rolling process, the bars are water cooled by a microcontroller having a controlled quenching chamber where temperature gradient travels from the core to surface.
The bar is taken out in the air after the intense cooling process and the core area heats quenched surface layer leading to tempering the external martensite. In this process, the heat flows from the core to the outer surface adding the needed strength to the material. This unique and extensive process makes these bar high standard one with an exceptional tensile strength and ductility. It also leads the bars to achieve an excellent bonding with concrete. They are definitely corrosion resistant.