What is the TMT Bar Manufacturing Process?

TMT Bars, or Thermo-Mechanically Treated Bars, are steel bars produced using the thermo mechanical process, which results in a hard outer core and a soft core while retaining bendability. They bond well with concrete and add strength to it. As a result, they are commonly used in the construction of reinforced concrete structures that are strong, long-lasting, and earthquake-resistant.

The following are the steps involved in the production of TMT bars:

1.Turning iron ore to iron - In this process, the primary materials, iron ore, coking coal, and limestone, are placed at the top of a blast furnace while hot air is blown at the bottom for combustion. The combustion of iron ore produces pig iron, which is free of several impurities found in iron ore. The limestone aids in the separation of iron from impurities and the transport of the iron to the surface in the form of slag.

2.Turning iron into steel - The molten pig iron is now poured into a basic oxygen furnace using a ladle. Around 20% of this vessel is also made of steel. A lance is lowered into the vessel, and high-pressure oxygen is blown through it. As a result, the oxygen reacts chemically with the carbon, burning impurities in the iron. Many impurities, such as oxides, silicates, and phosphates, react with the iron and form slag, or turn into fumes and escape through the top of the furnace when limestone is added to the mix. When molten steel slag is separated from it, it is ready to be mixed with other materials, formed into various alloys, and cast into any shape. Madhav KRG Group employs the well-known Ladle Refining Furnace (LRF) technology to ensure that the steel is free of harmful impurities such as phosphorus, sulphur, oxygen, nitrogen, and hydrogen. This technology aids in the production of 100% ISI tested billets suitable for the production of high quality TMT bars.

3.Rolling - The steel is then transferred to a Continuous Casting Machine (CCM) to produce billets.

4.Quenching - The first step in the thermomechanical treatment is quenching. Hot-rolled steel bars from the mill are cooled quickly with a water spray, resulting in the formation of a hard outer martensitic rim. The bar's core remains hot and austenitic. The TMT bar's two layers provide it with both strength and ductility.

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5. Self-tempering - After that, the steel bars are allowed to "self-temper." This step allows the core of the bar, which could not be cooled during quenching, to transfer its heat to the outer martensitic layer, "tempering" it and increasing its strength.

6.Atmospheric cooling – Finally, the steel bars are placed on a cooling bed and allowed to cool naturally. This allows the soft, inner austenitic core to be transformed into a ferrite-pearlite structure. As a result, the finished product has a tough hard order layer and a ductile core.