TMT Bars- its 4 [ grades manufacturing process & advantages]


Thermo Mechanically Treated (TMT Bars) is the bars having a soft inner core and tough outer core. Passing the steel wire through a rolling mill stand is the very first step on the manufacturing of TMT bars and these rolled steel wires are passed through the temp core water cooling system.

The water pressure is optimized while passing the wire through the water cooling system and change in temperature toughen the outer layer of steel bar and making it super durable and tough.

TMT Bars

TMT bars are the important construction material used for building homes, bridges, high rise buildings and many other constructions work because these bars show high strength to the structure and can stand with any kind of stress and load. These bars are thermo mechanically treated steel bars and also used to reinforce the concrete.

For various types of construction work these bars unique properties made them ideals such as super ductility, strength, and TMT bars are also earthquake resistant and to any concrete structure, these bars offer longevity and robustness.

Manufacturing Process Of TMT Bars:

These bars are made from steel and pass through a series of processes. Thermo Mechanical Treatment involves three steps in the manufacturing process;

Step#1: (Quenching)

A water spray system called Thermex System and hot roll bars release and enter the Thermex system and in the manufacturing process of the best quality of TMT bars Thermex technology is used. This technology ensures the ductility of these bars rebar and cools down the outer core rapidly and rapid cooling hardens the outer surface of TMT rebar and this cooling technique is called quenching.

quenching of tmt bars

Step#2:  (Self Tempering)

The core remains hot as compare to the surface of rebar once the TMT rebar is out of quenching and allows heat to flow from the core to the surface. This heat leads to the tempering of the outer layer and forms a tempered marten-site.

self tempering of tmt bars

Step#3: (Atmospheric Cooling)

When the process of self tempering gets over then for atmospheric cooling the TMT bar gets ready and in a normal temperature, cooling is done on a cooling bed.

For making TMT bar weldable and ductile this process increases the tensile strength and with ductility, the final product consists of a strong outer layer. The bars get ready for atmospheric cooling once the self tempering is over and austenitic core turns into the ferrite-pearlite structure. The final structure consists of a strong outer layer and this process increases the tensile strength.

The quality of TMT Bars depends on three major factors given below;

  1. Raw materials quality
  2. Rolling mill quality that gives the proper and uniform shape
  3. Quality system for tempering and quenching

Iron Ore To Steel:

In the production of TMT bars the raw material used in it includes iron ore, coal, and dolomite and these raw materials are mixed in the required quantities and are stacked and recovered. To increase the iron substances the iron ore goes through a beneficial process and to get into the shape of the mass of pellets metal fines are gathered.

For further purposes the coal is transformed to coke and to furnace the limestone and the existing materials are developed. Through a nozzle hot air is supplied to the furnace which results in the melting of raw materials and due to the melting of limestone its impurities come out which is called slag and being light in weight.

Primary Steel Making:

Oxygen is combined with carbon in iron in the initial stage of steelmaking which results in the elimination of carbon dioxide and this process is called pre-treatment.

For refining the steel, steel goes through the electric arc furnace and molten steel is transferred to a ladle and then to casting machine and sent to the water cooling mold. In the cold mold solidification happens and then cut into the required size.

Grades Of TMT Bars:

There are four grades of these bars as given below;

  • Fe 415 Grade:

For the common homeowners these bars are the choice due to its higher uniform elongation which makes them perfect for building structures in the area of earthquakes. They are resistant to corrosion and rust with the added advantage of anti-resistant coating.

  • Fe 500 Grade:

This grade of bars has been used in bridges, underground structures and multiple story commercial structures and due to their anti-corrosion-resistant properties they are popularly used in coastal areas.

  • Fe 550 Grade:

Where the scale of the project is slightly bigger for Fe 500 to handle, Fe 550 grade is used.

  • Fe 600 Grade:

The structure which requires strength and toughness, this grade is used and this TMT bars are known for its high tensile strength.

Weight Of TMT Bars As Per Size:

TMT Size

(1 Bundle)

TMT Rods per Bundle TMT weight per Bundle
8mm 10 47kg
10mm 7 53kg
12mm 5 53.4kg
16mm 3 56.88kg
20mm 2 59.2kg
25mm 1 46.2kg
32mm 1 75.72kg


Advantages Of TMT Bars:

There are following advantages of using these bars such as;

  1. These bars can be recycled without any loss of quality and are incredibly flexible.
  2. Into required steel frame these bars can be created.
  3. These bars can stand with earthquakes and fires.
  4. Due to their lightweight these bars are easy to transport.
  5. It can increase the pace of the construction process.
  6. These bars have strength combined with high ductility.
  7. Savings in the cost of the steel.
  8. Less affected by rust.
  9. To sustain fire it has more strength.
  10. While working with it these bars does not peel off the skin.



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