WHAT IS THE DIFFERENCE BETWEEN FE 500 AND FE 500D GRADE STEEL?

Fe 500 and Fe 500D are types of TMT steel bars as per the IS: 1786.

“Fe” stands for ferrous from which the TMT bars are made. The figure “500” implies the minimum yield stress in MPa. The letter “D” in Fe 500 D implies ductility which means that the steel bars have a higher percentage of elongation.

Fe 500 and Fe 500D have the same 0.2 percent proof stress/yield stress(Min) whereas the tensile strength is increased by 2 percent. Tensile strength(Min) for Fe 500 is 545 MPa and for Fe 500D it is 565 MPa.

Fe 500D has enhanced specified minimum percentage elongation i.e 16% whereas Fe 500 has a value of 12%
From the chemical composition point, Fe 500D has 0.25% Carbon (max) as compared to 0.30% (max) in Fe 500. Also, the maximum percentage of Sulphur and Phosphorous are lower in Fe 500D.

Fe 500D with lower quantities of carbon, sulphur and phosphorous, helps in preserving the steel and resisting earthquake shocks in future.

Elongation of the TMT bars and the strength of the rods on applying tension/force is higher in the D variant of the rods. These enhanced mechanical properties of the D grades TMT bars allow elevated resistance of the bars to natural calamities and also under stress.

Higher ductility is also highly seismic-resistant, hence it is preferred in earthquake zones 3, 4 & 5. It gives guaranteed elongation well above 16 %. 500“D” grade bars have balanced mechanical properties with higher ductility. They are found to be most suitable for constructing structures such as bridges, dams, high-rise apartments, industrial structures, flyovers, windmills, highway construction, earthquake-prone zones mountain bridges, railways bridges, structures such as airports, ports, hospitals cantilever structures, tunnels and concrete roads.

The following properties of “D” grade bars make them ideal for use in the construction of critical infrastructures:

1. TMT bars are resistant to earthquakes due to their soft pearlite core. Because of this, they can bear seismic and dynamic loading. 

2. TMT bars boast of high fatigue resistance to seismic loads because of high ductility and therefore they are widely used in earthquake-prone areas.

3. These bars have excellent bending capacity. Due to their flexibility, they can be moulded into different shapes by bending them up to any extent which ensures the modern living style.

4. TMT bars are completely earthquake resistant because of its elongation property. It can elongate up to 50% more than its original length without compromising on the measurements which helps to save on the construction as well.

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