The Part-I of this blog explained about the two most important factors to be considered in a TMT steel reinforced bar which was Tensile strength and Ductility. Also, a brief introduction of Ductility was described. The hot and soft inner ferrite-pearlite core is responsible for endowing the reinforced bar with optimum ductility. The ductility is not something that should be neglected. It is an integral part of handling the forces or loads of a building structure.
Hidden Ductility in Steel
As we know, there are many variations of the TMT reinforced bar classified as per their grades. They are Fe 500, Fe 550 and Fe 600.
Alright, have you ever wondered how these higher grades of TMT steel are produced?
You see, in order to achieve the so-called higher tensile strength, the ductility is reduced. Well, it is actually based on the three stages of the TMT process. The longer the reinforced bars are subjected to the process, the stronger the rebar becomes at the cost of ductility. Therefore the reinforced bar becomes brittle. The grades Fe 500, Fe 550 and higher are all produced by this method. Even the dealers typically promote higher grade steels by highlighting the strength parameters and purposefully hiding about the ductility issues.
The common man does not know the difference between strength and ductility. All he requires is that the steel bar should be “strong”. This lack of knowledge is exploited by certain dealers to promote their higher grade products. Usually, Fe 415 is sufficient for the construction of homes. Higher grades are only preferred if the design of the structure requires it.
Strength or Ductility?
In the TMT reinforced steel bar, both strength and ductility play major roles. Even though tensile strength is needed but a reinforced bar with more ductility handles stress better than a reinforced bar with less ductility. This is the sole reason why Fe 415 is the true grade TMT steel as it contains the right ratio of ductility and tensile strength unlike it’s higher cousins.