Flexibility is very critical for a steel bar so as to be able to withstand the sudden impact of extra loads or the effects of natural calamities. It is that which facilitates the bar to bend easily without breaking as well as possess the ability to be easily modified into any shape or size in line with requirements. All of it without the risk of getting cracks or turning down of the building structures.
When it comes to the best among the steel bars for flexibility, TMT bars are the most highly flexible with the best tensile strength. Add to this, they are also extremely fire-resistant, and corrosion-resistant. That is why they are preferred to other type of steel bars for construction activities. They are the most popular choice in highly earthquake prone nations like China, Indonesia, Japan, Mexico, India, etc.
WHAT MAKES TMT BARS SIGNIFICANT?
TMT (Thermo Mechanically Treated) Bar, also called as Reinforcing Bar or Rebar in CIVIL ENGINEERING terminology, is a high-strength reinforcement bar with a tough outer core and soft inner core. Since its evolution and eventual usage in construction projects, it has time and again proven to be extremely viable for reinforcing concrete structures. Today, TMT bars are commonly used as tensioning device to reinforce concrete, helping it resist compressive forces.
TMT is a process in which the steel bars are subjected to constant and repeated cooling to attain the maximum yield strength. Known for its high-strength, sturdy built and robust appearance with the capability to provide better reinforcement to any concrete structure, TMT Steel Bar is ideal for building earthquake-resistant structures.
They not only help to minimize the effects of damages during any seismic activities but they also offer the perfect optimum balance between toughness and flexibility (Elongation) with high thermal resistance. Further, they also possess high yield strength and greater tensile strength, flexibility, and ductility than mild steel.
They are not just ordinary steel bars but are extraordinary steel bars with enhanced strength and highly ductile and malleable in nature that is specifically designed for earthquake-resistant buildings.
WHAT MAKES TMT BARS SO FLEXIBLE?
TMT bars undergo thermal processing that involves compression and rolling through heat-treatment and water quenching; heating and cooling at various temperatures.
During the quenching process, the TMT bar (hot rolled bar) is quenched in a quenching box in a controlled environment. A special water system ensures that only the surface of the bar is cooled while the core part retains heat; then applies self-tempering to the bar by supplying heat to the surface. The outer layers harden into martensite which is very hard and highly-resistant to pressure or stress, while the core of the bar (inner surface) continues to stay soft, still austenitic. This will increase the bar’s tensile strength, improves its ductility, and imparts a high level of elongation to elevate its ability to withstand sudden high stress load bearing capacity in large-scale structures like dams, high-rise buildings, or flyovers.
Finally, the bar is passed through special cooling beds where the core gets transformed into a ferrite-pearlite-crytal structure which has high ductility. When the microstructure of the TMT bar is arranged in this manner, it ensures much better strength in the TMT bar to resist stress, also resulting in lowering of the building cost. This way, fewer number of high-strength TMT bars will be needed to create a construction structure, when compared to the number of ordinary bars used in identical situation.
At the end of it, all the TMT bars will have a variation in the structure with tougher martensite in the surface layer; martensite and the bainite in the intermediate layer; and a tough but ductile ferrite and pearlite core.
There is another process called the water-spray process that transforms the TMT bars intro highly tensile one’s making them easily moldable, called the ferrite-pearlite structure which gives the TMT bar its flexibility. In short, TMT bars attain flexibility when the outer surface hardens and the inner core remains soft.
Free of surface defects, TMT bars are much better at withstanding torsional stress making them highly corrosion-resistant with the highest flexibility and durable enough to be used in areas with high and regular seismic activity.
This test is called the ‘Bending & Re-bending’ test. Under this test, the TMT bar is bent to 1350 and kept in boiling water for about 30 minutes. Later it is re-bent to approximately 157.50.
The purpose of the test is to ensure that the TMT bars if designed for right amount of strength and flexibility should be able to easily bend without any appearance of surface cracks along its bends.
FLEXIBILITY ASPECT IN CONSTRUCTION
The construction process involves bar bending; it forms the crux of construction.
Bars need to be resized, bent, and shaped in line with construction requirements. This is where flexibility comes to fore which TMT bars can display, without putting much effort or time; easily bending to required sizes and moulding into required shapes. This in turn will consume less manpower work and man-hours while the overall construction work will get completed on schedule with efficiency.
When pushed by an external force, the tough outer core and soft inner core of the TMT bar will allow it to bend to an extreme degree and later evolve back to the original shape, all of it without much strain. This is what is called flexibility that gives the TMT bars their inner strength to withstand all odds.
The flexibility of TMT bars in turn gives them the quality of extra elongation without compromising the measurement. For superior elongation, the bars can be bent and re-bend up to 180 degrees without any harm to the TMT bars. That is how they are able to withstand the extra load from any external force, from earthquakes to floods, hurricanes. Etc.
According to ISO, Fe500D grade TMT bar possess the perfect balance of flexibility and strength, which makes it ideal for sudden load absorption. It is also cost-effective when compared to other grades; uses only 17-20% lesser quantity of steel. Furthermore, it makes for ideal lightweight transportation and with its superior ductility, it is ideal for all kinds of construction purposes.
VINAYAK STEEL TMT BARS – MOST VIABLE CHOICE
With growing demand for quality TMT steel bars, finding the appropriate TMT bars for construction needs will become more paramount.
Currently, there are various grades of TMT bars available in the marketplace. Each of the grades represents the strength and rigidity of the TMT bar, specifically the yield-strength of reinforcements. When zeroing in on the right TMT bars, factoring in the strength of TMT bars based on their grades, is important. The higher the grade, the better the TMT bars are. It is here that Fe 500D Grade TMT Bars provides the ideal confluence of strength & flexibility in line with IS Standards. Further, their extreme flexibility in line with the same norms makes them ideal for all types of construction purposes.
Leading TMT steel bars manufacturer, VINAYAK STEEL INDUSTRIES offers the finest of genuine strongest and long-life TMT steel bar Fe-550, that conform to IS: 1786:2008 BIS standards (a standard equivalent to a number of international standards like ASTM A615 Grade 60 of the USA; BS 444 Grade 460 of Britain; BST 500 of DIN 488 of Germany).
VINAYAK STEEL’s high-grade Fe-550 TMT Bar has proven time and again its extreme robustness and strength. Add to this, it also guarantees top-notch equilibrium, safety and stability to a concrete structure; and great resistance on dynamic loading with varied yield and tensile strength.
Further, as per ISO standards, Vinayak Steels Fe-550 grade TMT bars possess the ultimate tensile strength of 585 N/mm2. Chemical composition is another factor that gives Vinayak Steels Fe-550 grade TMT bars, solid flexibility.
Manufactured with the latest technology, every Fe-550 TMT Bar undergoes robust quality-check process including extreme anti-corrosion testing methodology, in intense rusting conditions. Furthermore, chemical composition is maintained meticulously at the manufacturing plant to standards prescribed by ISO, to ensure optimized flexibility.
The high calibre of their quality can be estimated from the fact that every VINAYAK’s Fe-550 TMT Bar, carries a BIS Certification confirming adherence to IS 1786:2008 (Contains the Standard Mark, Cast / Lot number, Grade, Size, & Corresponding test results).
An ideal construction material for all kinds of construction structures from coastal, to marine or underground, the Vinayak Fe-550 TMT Bars from Vinayak Steels Limited, hyderabad are best suited and in accordance with the design requirement of a construction structure.