TMT or Thermo-mechanical Treatment is a process followed to make TMT steel bars. TMT bars are new-generation-high-strength steel with superior properties. These bars are known for their weldability, strength, ductility, and flexibility which has helped them to meet the highest quality standards. Construction of TMT bars are one of the popular uses of steel coils.
TMT bars are steel bars used in any kind of construction work. These bars form the spine and frame of buildings in the modern-day world. Heavy load bearing structures of bridges, ports, stations, or commercial structures like residential or office complexes, schools and hospitals, high rises and malls, all these structures use TMT bars as a building raw material.
Advantages of using TMT Bars in construction:
- Lightweight and easy to transport
- Can withstand fires and earthquakes
- Superior malleability, ductility, strength, and weldability
- Recyclable and reusable without loss of quality
Manufacturing process of Steel TMT bars
The manufacturing of TMT steel bars uses the metallurgical process. This includes mechanical deformation such as compression, forging, and rolling with thermal processes such as heat treatment and quenching. TMT process means treatment of a steel rod by exposing it to a high temperature and then rapidly cooling the periphery, creating a hard material layer called martensite.
Let us take a deep dive into the TMT bar manufacturing process. TMT bar making follows four steps:
- Heating, rolling, and forming of reinforced steel bars
This is the first step in the TMT bar manufacturing process. The raw material for making TMT bars is steel billets. These billets are made by converting iron ore to iron and converting the iron into steel billets. The methods used to convert iron to steel have advanced considerably and now there are various methods followed by steel makers to increase the strength and durability of the steel.
To make TMT bars the steel billets are first heated to approximately 1200 °C to 1250 °C. These are then rolled into the final size and shapes in the form of a reinforced bar by putting them through a rolling mill stand. This is often referred to as the TMT rolling mill process.
After the TMT bars leave the rolling mill stand, they immediately undergo rapid cooling in a quenching box. This box applies pressurised water via a special nozzles system to help the bars obtain certain material properties.
When the hot reinforced bar leaves the final rolling mill stand, it is instantaneously quenched – a type of heat treatment where the rebars are rapidly cooled by water in a quenching box to obtain certain material properties. The rapid cooling toughens the outer layer of the steel bar, thus improving its tensile strength and durability.
Quenching converts the outer surface of the reinforced bar to Martensite. Martensite is a hard form of steel that causes it to shrink pressurising the core. This process helps to form the correct crystal structures. Therefore, quenching makes the outer part of bar become cold and hardened while the core remains hot.
After the bars leave the quenching box, the core remains hot compared to the surface. This allows heat to flow from the inner core to the surface causing tempering of the outer Martensite layer thus forming a structure called ‘Tempered Martensite’. This increases the strength of the TMT bar.
- Atmospheric cooling
After the self-tempering process, the bars undergo atmospheric cooling to equalise the temperature of the soft inner core and the hardened Martensite layer. Once the bars are completely cooled down, the final structure will have a strong outer layer with a ductile core. This process increases the tensile strength that makes TMT bars highly ductile and weldable.
The quality of TMT bar depends on three factors:
- Quality of raw materials
- A superior rolling mill stand
- Advanced quenching and tempering technology
The TMT bar manufacturing process ensures that the steel bars have desired properties.
There are many TMT bar manufacturers in India guaranteeing the best quality TMT steel bars. If you are looking to source the best TMT steel bars, visit Tata nexarc to contact trusted sellers who offer high quality TMT bars.