TMT bars

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TMT bars

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Reinforcement bars Overview

In order to fulfill industry need to make construction faster and economical, reinforced concrete structures replaced earlier building styles.Steel reinforcement was done with a view to supplement the weak tensile strength of concrete.

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Overview Reinforcing was done with

Plain steel bars till 60’s Low strength Low surface area resulting poor grip

CTD bars replaced plain steel bars in 60’s

High strength Larger area of projection to ensure better

grip, but Non uniform strength Low ductility due to work hardening Low resistance to corrosion

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Overview

TMT Bars introduced in 70’s to overcome shortcoming of CTD bars.

These are produced using new technology to ensure higher strength, better ductility, and resistance to corrosion.

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Reinforcement bars Overview

Methods for increasing Yield Strength

As Rolled TMT Cold Deformed

Increase % C,Mn

Addition of Nb, V

Weldability Cost

Heat Treatment from the heat of Rolling

Improved Quality

Twisting, Drawing, Cold Rolling

Work Hardening and residual stress

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Process Overview TMT process is producing desired

mechanical properties in a bar using heat treatment

Rolls

Rolls

Water Quenching

Water Quenching

Bar under Rolling

Cooling Bed

Bar under Cooling

TMT Bundles

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Process

In TMT process bars are produced by rapid cooling of steel being rolled. This produces hardened structure called “tempered Martensitic steel” on the outer surface, while inner core remains soft “Ferritic Pearlitic steel.”

The combination of these two factors gives excellent yield strength to the bar along with superior ductility & weldability.

Ferritic Pearlitic steel

tempered Martensitic steel

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Product Advantages In the past, the conventional ribbed cold

twisted bars were used in RCC structures. The bars had inherent problems of poor weldability & ductility. Additional operation of cold twisting induced residual torsional stresses and became less corrosion resistant due to stresses and removal of preventive mill scale coating.

TMT process eliminates all these undesirable attributes. They attain higher strength, excellent ductility, bendability and superior weldability due to lower carbon content.

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Features & Benefits Lower carbon content and made from

fully killed steel. Higher yield strength, ultimate tensile

strength, % elongation when compared to CTD bars of same grade.

Easy bendability, weldability and ductility ensures economy and safety in use.

In-built ability to resist loss of strength at higher temperature.

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Features & Benefits

Require less energy for bending and re-bending along with superior reverse bending properties.

Can be butt or lap welded. Use of Fe 500 grade results in up

to 15 % saving in steel consumption.

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Applications

TMT bars can be used in all the applications of reinforced cement concrete structures, where the soil possesses corrosive characteristics due to salinity owing to excellent corrosion resistance or under seismic conditions because of their higher energy absorbing capacity.

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