What is the procedure for producing TMT bars?

 Thermo-Mechanically Treated Bars, or TMT Bars, are steel bars that have a hard outer core and a soft inner core while retaining their pliability. They bond well with concrete and enhance its durability. Therefore, they are commonly employed in the construction of reinforced concrete structures that are robust, durable, and reasonably earthquake-resistant.

Several steps are involved in the production of TMT bars, which are as follows:

1.Turning iron ore into iron - In this process, iron ore, coking coal, and limestone are placed in the upper portion of a blast furnace, while hot air is blown on the surface below for combustion. Pig iron is produced by the combustion of iron ore and is free of several impurities present in iron ore. The limestone aids in separating iron from impurities and bringing slag to the surface.

Pouring molten pig iron into a basic oxygen furnace with a ladle, the second step in the transformation of iron into steel is now complete. Approximately twenty percent of this vessel is also composed of steel. A lance is lowered into the vessel, and high-pressure oxygen is blown through the lance. This results in the oxygen undergoing a chemical reaction with the carbon and burning impurities in the iron. As impurities such as oxides, silicates, and phosphates react with and form slag, or turn into fumes and escape from the top of the furnace, the limestone, which is part of the mixture, assists in further cleaning the iron. When slag is separated from molten steel, it is ready to be combined with other substances, transformed into various alloys, and cast into any desired form. Madhav KRG Group employs the well-known Ladle Refining Furnace (LRF) technology, which ensures that the steel is free of phosphorus, sulphur, oxygen, nitrogen, and hydrogen. This technology enables the production of 100% ISI-tested billets that are ideal for transforming into high-quality TMT bars.

Also check: CRS Bars in South India

After this, the steel is transferred to a Continuous Casting Machine (CCM), which produces billets.

4.Quenching - The first step of the thermomechanical treatment is now quenching. A water spray is used to rapidly cool hot-rolled steel bars from the mill, resulting in the formation of a martensitic rim. The bar's centre remains hot and austere. The TMT bar's two layers give it both strength and pliability.

Self-tempering - At this point, the steel bars are allowed to "self-temper." During this step, the core of the bar, which could not be cooled during quenching, transfers its heat to the outer martensitic layer, "tempering" it and increasing its strength.

6.Atmospheric cooling - Lastly, the steel bars are placed on a cooling bed and allowed to cool to room temperature. This allows the soft inner austenitic core to transform into a ferrite-pearlite structure. Thus, the final product has a tough outer layer and a ductile centre.