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TMT Steel Bar

 

Staying true to its Slogan "Always First, Always Ahead", Panchakanya Steel in the year 2002 became the first Company in Nepal to manufacture TMT steel bars, a new generation high strength ribbed reinforcement bar using Thermo Cooling Technology, licensed under Hennigsdorier Stethi Engg. GmbH (HSE), Germany. Panchakanya Group’s commitment towards excellence in quality production was fulfilled when it was recognized as the First steel industry in the country to be bestowed the prestigious NS mark and NS quality award certified by Nepal Bureau of Standard. Besides it also became the first industry in Nepal to be certified ISO: 9001:2008 by Lloyds' Quality Assurance Register. Also for its effective and efficient management of its environmental system, Panchakanya Steel was bequeathed with ISO: 14001:2004 certifications by DNV Certification B.V, The Netherlands.

TMT Steel Size

TMT Steel Sizes 8mm (10 - 20)mm 25mm 28mm 32mm

 

Panchakanya TMT STEEL
Thermo-mechanical treatment (TMT) is a metallurgical process that integrates work hardening and heat-treatment into a single process.

The quenching process produces a high strength-bar. The process quenches the surface layer of the bar, which pressurizes and deforms the crystal structure of intermediate layers, and simultaneously begins to temper the quenched layers using the heat from the bar's core.

The Process
Steel billets ("pencil ingots") are heated to a high degree heat in a reheat furnace. Then, they are progressively rolled to reduce the billets to the final size and shape of reinforcing bar. After the last rolling stand, the billet moves through a quench box. The quenching converts the billet's surface layer to martensite, and causes it to shrink. The shrinkage pressurizes the core, helping to form the correct crystal structures. The core remains hot, and austenitic. A microprocessor controls the water flow to the quench box, to manage the temperature difference through the cross-section of the bars. The correct temperature difference assures that all processes occur, and bars have the necessary mechanical properties.

The bar leaves the quench box with a temperature gradient through its cross section. As the bar cools, heat flows from the bar's centre to its surface so that the bar's heat and pressure correctly tempers an intermediate ring of martensite and bainite.

Finally, the slow cooling after quenching automatically tempers the austenitic core to ferrite and pearlite on the cooling bed.

These bars therefore exhibit a variation in microstructure in their cross section, having strong, tough, tempered martensite in the surface layer of the bar, an intermediate layer of martensite and bainite, and a refined, tough and ductile ferrite and pearlite core.

TMT ADVANTAGES:

  • Earthquake resistance: The soft ferrite-pearlite core enables the bar to bear dynamic and seismic loading. TMT bars have high fatigue resistance to Dynamic/ Seismic loads due to its higher ductility quality. This makes them most suitable for use in earthquake prone areas.
  • Better Safety of structures: because of higher Strength combined with higher Ductility.
  • Easy working at site: owing to better Ductility and Bendability. Pre-welded meshes can be made to eliminate manual binding at site. Reduces construction and fabrication time.
  • Resists fire: Unlike TOR steel/ CTD Reinforcement bars, TMT bars have high thermal stability. They are the preferred choice when elevated temperatures of 400-6000 C may be encountered.
  • Resists corrosion: The TMT process gives the bar superior strength and anti-corrosive properties. Controlled water-cooling prevents the formation of coarse carbides, which has been cited as the main cause for the corrosive nature of common bar.
  • Another reason for better corrosion resistance is the absence of surface stresses caused by the cold twisting process.
  • Formability: Due to very high elongation values and consistent properties throughout the length of bar, TMT rebar’s have excellent workability and bendability.
  • Malleability: TMT bars are most preferred because of their flexible nature
  • Fine welding features: TMT rebar’s (having low carbon content) can be used for butt and other weld joints without reduction in strength at the weld joints.
  • Bonding strength: External ribs running across the entire length of the TMT bar give superior bonding strength between the bar and the concrete.

Mechanical Properties of Steel Bars

Characteristics NS 191 Requirement for grade - fe415 (CTD) NS 191 Requirement for grade - fe500 (TMT) Typical values for PK Thermex TMT steel bars
0.2% Proof Stress Yield/Stress (N/mm²) 415 min. 500 min. 510-574
Ultimate Tensile Strength (N/mm²) 485 (10% more than actual 0.2% proof Yield Stress) 545 (8% more than the actual Yield Stress) 590-650
Elongation % on gauge length 5.65. √Ago (Where ‘Ago’ is the cross sectional area) 14.5 min. 12 min. 16-25
Bend Test

 

Up to and including

22 mm
Over 22 mm

No transverse cracks in the bent portion on bending to 30%°,

Mandrel
Diameters

No transverse cracks in the bent portion on bending to 30%°,

Mandrel
Diameters

No transverse cracks in the bent portion
Rebend Test

 

 


Up to and including

10 mm
Over 10 mm

No fractures in the bent portion and rebending to 157.5°-135° after keeping in the boiling water for 30 minutes and subsequent cooling at ambient temperature.

Mandrel
Diameters

No fractures in the bent portion and rebending to 157.5°-135° after keeping in the boiling water for 30 minutes and subsequent cooling at ambient temperature.

Mandrel
Diameters

There is no fraction in bent portion

 

 

 


Mass Chart

Normal Diameter (mm) Cross Sectional Area (mm) Normal Mass Per (Kg/Mtr.) Normal Strength (Mrt./Mton) Tolerance on Normal Mass
8 50.0 0.395 2500 +/- 7%
10 78.6 0.617 1600 +/- 7%
12 113.1 0.888 120% +/- 5%
14 154.0 1.209 827 +/- 5%
16 201.1 1.579 633 +/- 5%
18 254.6 1.998 500 +/- 3%
20 314.3 2.467 400 +/- 3%
22 380.3 2.985 335 +/- 3%
25 491.1 3.855 260 +/- 3%
28 616.0 4.836 200 +/- 3%
32 804.6 6.316 158 +/- 3%

Comparison Chart
THERMEX TMT Grade Fe- 500 vs. TOR Steel and CTD Grade Fe- 415

Parameter CTD/ TOR Fe- 415 Panchakanya TMT Fe- 500
Yield Strength N/mm² 415 min. 510-570
Tensile Strength N/mm² 485 min. 590-650
Elongation % 14.5 min. 16-25
Corrosion Rusts easily and quickly Corrosion Resistance
Weldability Poor Excellent
Use of High Temperature - Safer
Use in Earthquake Areas - Preferred
Consistency High variance in Properties High
Bend Properties - Superior
Saving in Steel Used - Minimum 10%
Global Use Not Permitted Preferred Choice
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