The grade represents the amount of stress a bar can take and is measured in N/mm2.
Higher the grade better is its stress taking capacity.
The four grades of TMT Steel bars are :
|Grade||Fe 415||Fe 500||Fe 550||Fe 600|
|Stress Capacity||415 N/mm2||500 N/mm2||550 N/mm2||600 N/mm2|
The most common type of grade used in construction is Fe 500, which means that it can take stress upto 500N/mm2.
There is no much difference between the fe 500 and fe500D though both are of the same grade the fe 500D is more ductile in nature and helps it to withstand sudden load absorption capacity, which is encountered during earthquakes, cyclones and other natural calamities.
The higher grades of bars such as Fe 600 are not generally available and are made on order.