Behind the Manufacturing: Knowing the Production Process of TMT Bars

Behind the Manufacturing: Knowing the Production Process of TMT Bars

TMT bars are manufactured using high strength steel and possess a range of desirable qualities, making them the no. 1 preference for construction projects. The unique design of TMT bars and the use of latest technology in manufacturing enhance their strength and quality further.  Keep reading to know the step-by-step manufacturing process of these thermo-mechanically treated building essentials.

Iron ore converted to molten iron

  • Obtaining raw material and processing it – Necessary raw materials, like iron ore, coal, limestone and dolomite (fluxes) are mined from different locations.  After this they are piled, recovered and mixed in requisite proportions.

  • Beneficiation and transforming coke to coal – The iron ore undergoes beneficiation process to raise the iron content. Then ore fines are collected to form a mass of pellets and sinter to improve productivity. The coal is changed to coke for future use.

  • Iron making – Coke, sinter and ore, accompanied by limestone, are supplied to the peak of the furnace. Through nozzles, hot air is fed to the base of the furnace. This causes the iron in the ore along with sinter to melt out and form a pool at the bottom of the furnace. Limestone combines with impurities forming a liquid called ‘slag’, which is lighter than metal and floats on the surface of molten metal.

  • Molten iron  changed to steel and casting

  • Primary steel making – In a Basic Oxygen Furnace, the molten iron first undergoes pretreatment before being transformed to steel. The oxygen combines with carbon in the iron and gets eliminated as carbon dioxide.

  • Secondary steelmaking – The steel further goes through treatment in a LHF (Ladle Heating Furnace), refining the composition of steel.

  • Continuous casting – The molten steel in poured into a casting machine that churns out billets.

  • Thermo mechanical treatment

  • Quenching – As soon as a heated rolled bar departs from the mill stand, it is quenched using various types of heat treatments. Following this the rebars are quickly cooled with the water spray system present in the quenching unit. This process is useful for obtaining specific material properties and hardening the outer surface while keeping the core soft and hot.

  • Self-tempering – The core being at a higher temperature even after exiting the quenching box, continuously supplies heat to the outer surface. This leads to the tempering of the outer surface, which changes to the structure Tempered Martensite. At this stage, the core remains austenitic, a cubical crystalline structure.

  • Atmospheric cooling – After the self-tempering process, the bars go through atmospheric cooling, carried out at room temperature.  The process happens on cooling beds; during this step the austenitic core gets converted into the ferrite-pearlite structure. Thus, the final structure consists of tempered martensite layer in the periphery, which is highly strong, and the ferrite core that is very ductile.

MSP Steel, a reputed TMT bar manufacturer, provides TMT bars that have excellent strength and ductility, resulting in buildings that are well designed and stand protected against catastrophic earthquakes. To stay updated with the trends and news of the Indian Steel Industry, visit our website.


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