What is TMT ?

Thermo Mechanically Treated steel also known as TMT steel can be described as a new-generation-high-strength steel having superior properties such as:

  • Weld ability
  • Strength
  • Ductility and
  • Bendability meeting highest quality standards at international level.

Under thermo mechanical treatment of bars, the steel bars are made to pass through a specially designed water cooling system where these are kept for such a period that outer surface of bars becomes colder while the core remains hot.

This creates a temperature gradient in the bars. When the bars are taken out of the cooling system, the heat flows from the core to the outer surface causing further tempering of steel bars thereby helping them in attaining a higher yield strength of steel.

How TMT steel bar manufactured ?

TMT steel bars are produce from Carbon steel material(BILLETs/,INGOTS)Finish steel bar coming out of finishing stage of rolling mill is passed through devise where it is being passed through high pressure water jets to give the steel bars desire quality's 500/550Kg per cms.squre

What does Fe 415 and Fe500 steel mean?

Fe stands for Ferrous material ie iron from which the reinforcement steel bars are manufactured.

The reinforcement steel bars used in RCC (Reinforced Cement Concrete) are designated as

  • Fe415 (or)
  • Fe500

Depending on their Yield Strength. (The numbers 415 and 500 tell about this Yield Strength in N/mm2 the bars are designed and manufactured to have.)

As per IS : 1786 Yield Stress (also known as 0.2% proof stress) of Fe 500 is 500 N/mm2.

So, Fe500 steel means the reinforcement steel rods (or bars) that can safely withstand an Yield Stress of500 N/mm2.

N/mm2 stands for newton/Square millimeter

What is the difference between 'Fe415 steel' and 'Fe500 steel'?

They each refer to different grades of steel.

The reinforcement steel bars used in RCC (Reinforced Cement Concrete) are designated into grades asFe415 or Fe500 depending on their Yield Strength.

The numbers 415 and 500 tell about this Yield Strength in N/mm2 the bars are designed and manufactured to have.

Differences between 'Fe415 steel' and 'Fe500 steel':

  • Fe415 has a minimum Yield Strength of 415 N/sq.mm and Fe500 has a minimum Yield Strength as 500 N/sq.mm.
  • The minimum Ultimate Tensile Strength (UTS) of is 485 N/mm2 and that of Fe500 is 545 N/mm2.
  • The minimum Percentage Elongation for Fe415 is 14.5 and that of Fe500 is 12.

What is formula to calculate the area of steel bar?

For surface area of steel bar= pi*diameter*length For cross-sectional area of steel bar= pi (dia)^2/4

What is difference between Fe500 and 500 D TMT bar?

  • The grade of steel is same for both it is 500N/mm2, but FE500D is more ductile than the FE500.
  • This enables the fe500D to withstand the sudden load adsorption capacity, which is encountered during earthquakes, cyclones, Tsunamies etc providing higher safety.
  • This shall be mainly used in the high seismic prone zones.

Formula for calculating section weight per meter

There is a simple formula to calculate the weight as follows.

Section Weight as per IS 1786
Item square /162 = kg/ mtr weight

For Example – calculation of 8 mm and 16 mm TMT BARS will be as follows :

8 X 8 / 162 = 0.395 kg/mtr weight
16 X16 / 162 = 1.58 kg/mtr weight

Section Weight as per IS 1786

Size of Bars Kg / mtr
Minimum Standard Maximum
8 mm 0.367 0.395 0.432
10 mm 0.574 0.617 0.66
12 mm 0.844 0.888 0.932
16 mm 1.501 1.58 1.659
20 mm 2.396 2.47 2.511
25 mm 3.735 3.85 3.966
28 mm 4.685 4.83 4.975
32 mm 6.121 6.31 6.499

As per IS Grade 1399 – Mandrel Diameter for Bend Test :

Mandrel Diameter for Different Grades
Fe500 Fe500D Fe550D
8 mm to 20 mm 4 Φ 3 Φ 5 Φ
Over 20 mm 5 Φ 4 Φ 6 Φ
Where Φ is the nominal size of the Bar, in mm E.g. 8 mm : 4 Φ that means for 8 mm Fe500 require 8 X 4 i.e. 32 mm mandrel min

TMT Bar- ReBend Properties :

Sr.No. Diameter of Rod Mandrel for Fe-415 & 500 Bend Mandrel for Fe-415 & 500 Re Bend
1 08 mm 24 & 32 mm 40 mm (5 → Z)
2 10 mm 30 & 40mm 50 mm (5 → Z)
3 12 mm 36 & 48 mm 84 mm (7 → Z)
4 16 mm 48 & 64 mm 112 mm (7 → Z)
5 20 mm 60 & 80 mm 140 mm (7 → Z)
6 25 mm 100 & 125 mm 175 mm (7 → Z)
7 28 mm 112 & 140 mm 196 mm (7 → Z)
8 32 mm 128 & 160 mm 224 mm (7 → Z)
9 36 mm 144 & 180 mm 252 mm (7 → Z)
10 40 mm 160 & 200 mm 280 mm (7 → Z)

Chemical Composition :

Grade C% (Max) S% (Max) P% (Max) Mn% (Max) Si% (Max)
Fe-415 0.25 0.055 0.055 0.055 0.3
Fe-500 0.25 0.05 0.05 0.06 0.3
Fe-500D 0.25 0.045 0.045 0.075 0.3

Mechanical Properties :

Properties Fe-415 (%) Fe-500 (%) Fe-500 D (%)
Yield Stress, N/mm2 415 500 500
Tensile Strength 485 545 565
Elongation 14.5 12 16

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