My previous blog explained the stages of manufacturing TMT steel bar grade Fe 415 and special TMT grades bars. Did you know that Fe 415 is called a true grade TMT steel bar?
Have you wondered why Fe 415 is the true TMT grade?
It’s the original TMT bar that provides an optimum high tensile strength and ductility and by changing its manufacturing process slightly, produces different variations with higher strengths but less ductility TMT bars called the special TMT bars such as Fe 500, Fe 550, Fe 600.
That’s right, you read it right, “less ductility”. How does it affect TMT steel grades having higher strength? This is a fact most common people wouldn’t care about, because either they are not aware of it or certain companies hide this fact to promote higher grade TMT steels by marketing its strength alone.
Ductility is a measure of a material’s ability to undergo significant deformation(bending) before breaking. It is expressed as percent elongation or percent area reduction from a tensile test. Ductile material could be stretched to a rod or a wire depending on its ductility. Bending metal requires the metal to be ductile. TMT steel bars are known for their superior yield strength and ductility.
If the TMT steel bar is more ductile it’s elongation percentage will be more till the point it breaks. The elongation percentage of Fe 415 is 14.5% whereas for Fe 500 it is 12% even though Fe 500 has higher tensile strength than Fe 415. Now you know which is more ductile.
The opposite of ductility is brittleness, where a material breaks when tensile stress is applied to lengthen it. Here brittleness is resulted due to compromising of ductility in order to increase the strength of the TMT rebar. If buildings constructed using higher grade steel rebars eg. Fe 500, with less ductility i.e Brittle, it is not technically protected even if it has a high tensile strength and in the event of earthquakes, the building will collapse. A brittle TMT steel bar will crack with even a small amount of bending.
The true TMT steel rebar
The Fe 415 is one of a kind because it is the only TMT steel rebar that has an optimum high tensile strength and ductility. Even though the Fe 500 and other grades have higher strength than Fe 415, what makes Fe 415 unique is that its ductility is higher than its counterparts. Therefore, it has a longer elongation percentage i.e. it can bend more without breaking. Normally Fe 415 is sufficient for homes and higher grades are needed only if the design specifies it.