The quality of TMT steel is one of the most important factors that determine the strength and longevity of a structure. However, to be able to decipher and determine the quality of TMT steel bars and hence choose the best steel company for your construction, it is important to first understand the TMT steel bar manufacturing process.
Once you know the process, you will be able to judge any TMT manufacturer based on the adherence to the various steps in the process, and hence ensure that you get nothing but the best quality TMT steel.
TMT steel manufacturing process primarily involves three main steps.
- Procession of raw iron ore for steel making
- Conversion of iron to steel
- Thermo Mechanical Treatment & Hot Rolling
Each of these steps is fundamental to the manufacturing of TMT steel. Let us tell you in detail, what goes into and what really happens in each of these steps.
3 Steps of Steel Bar Manufacturing Process
STEP 1: Processing of raw iron ore for steel making
The starting point or the raw material that goes into steel manufacturing is primarily iron ore. First of all, the iron ore is processed, mixed, and unmixed as per the requirements of TMT steel. Coal and dolomite also go into the process.
During the first stage of the process, the iron ore goes through beneficiation which leads to a rise in the iron substance. Here, the metal fines are gathered together which leads to an improvement in the efficiency of the substance.
By the end of this step, the iron ore gets purified, the required materials are mixed with it in the requisite proportions, and all the impurities get accumulated separately in the form of slag.
STEP 2: Conversion of iron to steel
During this step, oxygen is combined with carbon in the iron ore, with the help of an oxygen furnace. This pre-treatment eliminated carbon dioxide from the mixture. After this, the under-process steel is passed through EAF (Electric Arc Furnace) for the purpose of further refining its composition.
Now begins the very important step of casting in the form of TMT steel rods in a steel factory. Molten steel from EAF (Electric Arc Furnace) is gradually transferred to the continuous casting machine, from where it flows further into the water-cooled molds. Solidification happens at this step as the steel now takes the shape of TMT bars.
STEP 3: Thermo Mechanical Treatment
The third and final step in TMT steel bar manufacturing, which is Thermo Mechanical Treatment, itself, comprises three sub-steps.
These three essential steps are:
- Quenching
- Self Tempering
- Atmospheric cooling
The process of quenching is meant to fine-tune the hardness and ductility of the steel bars in making, and ensure the right and desired properties. As soon as the hot rolled steel bars get out of the finished mill, they are thrown into a water spray system known as the ‘Thermex System’. In the process, the temperature of the outer layer of the steel bars is brought down rapidly, which leads to its hardening while the inner core remains hot and flexible. This entire process is called as ‘quenching’ of the steel bars.
After the completion of the quenching process in the Thermex system, the steel bars are allowed to ‘self-temper’ themselves. What this means is that now the heat from the relatively warmer inner core of the bars flows towards the outer rim, causing automatic tempering of the outer Martensite layer. The structure thus formed on the outer surface of the bars is known as ‘Tempered Martensite’.
The third and final sub-step in the Thermo Mechanical Treatment of steel bars in the TMT steel factory is known as Atmospheric Cooling. Post self tempering, the almost ready TMT steel bars are put on a cooling bed, which is at the normal atmospheric temperature. During this step of atmospheric cooling, the austenitic core of the bars turns into a ferrite-pearlite structure.
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As a result of this entire process, the output, that is the TMT steel bars that we get display peculiar and desirable properties. These bars have a strong and robust outer layer while the inner core is adequately soft and flexible. Such a structure improves both the tensile strength and ductility of the TMT steel bars.
The Bottom Line!!
Now that you know the elaborate process that goes into the manufacturing of TMT steel, you must make the choice of TMT steel manufacturer consciously. In fact, you should source TMT steel bars only from a top-class TMT steel company such as Sugna TMT which ensures quality and excellence at each step of the manufacturing process.