Frequently Asked Questions about TMT-Steel

For the first time in history, RADHA SMELTERS has ventured into product branding and has forayed into retail with the launch of Radha 550 TMT Bars. These TMT Bars are technically advanced, thermo-mechanically treated and are different from other bars because of the state-of–the art THERMEX technology invented by Sir Franz Tamm of Hennigsdorfer Stahl Engineering GmbH, leaders in Quenching & Self Tempering (QST) Technology.

Thermo Mechanical Treatment (TMT) or processing, is a metallurgical process that integrates work hardening and heat treatment with one single process. The Thermex - quenching process produces bars from low carbon steel which are of very high strength. The process quenches the surface layer of the bar, which pressurizes and deforms the crystal structure of the intermediate layers, and simultaneously begins to temper the quenched layers using the heat from the bar's core.

TMT steel bars are of very high strength and compliments “Reinforced Cement Concrete” (RCC) which has become an integral part of every structure. TMT together with RCC can be molded into any desired shape with which the Steel Bars are able to withstand any load put upon them. TMT Bars should conform to the best in class quality standards, so that the risk of unforeseen forces that may develop because of any live or dead load acting upon the structures, that may cause loss of life and property can be avoided. Only TMT bars should be used to secure the structural creations of mankind and to make them sturdy and long lasting for generations to come.

To make any structure strong and durable only TMT bars should be used. It can be used for all types of construction works ranging from single storied houses, multi-storied buildings/complexes, tunnels, bridges, flyovers, dams, or even TV towers. Developed countries use only TMT bars for every type of construction - small or big.

The commonly manufactured and used grades are Fe - 415, Fe - 500, Fe – 550 and their D types also. RADHA 550 TMT BARS have the highest tensile and load bearing strength amongst all the grades.

Radha TMT manufactures high strength TMT Bars in Fe 500 & Fe 550 grades conforming to IS 1786:2008 standards.
The sizes available are 8mm, 10mm, 12mm, 16mm, 20mm, 25mm, 32mm.
All the bars manufactured by RADHA TMT use the Thermex process.

The following table demonstrates the chemical and mechanical properties:

Chemical properties of TMT bar as per IS:1786-2008

GRADE FE-415 FE-500 FE-550 RADHA FE-550
Carbon % <0.30 % <0.30 % <0.30 % <0.25 %
Sulphur % <0.060 % <0.055% <0.055% <0.050%
Phosphorus % <0.060 % <0.055% <0.050% <0.050%
Sulphur+Phosphorus % <0.110% <0.105% <0.100% <0.100%
Carbon Equivalent % <0.42% <0.42% <0.42% <0.40%

Mechanical properties of TMT bar as per IS:1786-2008

GRADE FE-415 FE-500 FE-550 RADHA FE-550
Yield Stress(N/mm2) >415 >500 >550 >570
Tensile Strenght(N/mm2) >485 >545 >585 >640
Elongation % >12% >10% >16%

Yield stress: Is the stress a TMT can withstand without permanent deformation., Yield strength is usually stated as the stress at which a permanent deformation of 0.2% of the original dimension will result, known as the 0.2% yield stress. OR The stress at which a non-proportional elongation equals to 0.2 % of the original gauge length takes place (where gauge length is 5.65sqrt A. ’A’ is the cross sectional area of the test piece).


Ultimate Tensile Strength: The maximum stress a material can withstand in a tensile test. OR The maximum load (force) reached in a tensile test divided by the effective cross sectional area of gauge length portion of the test piece.


Percentage Elongation: When a material is tested for tensile strength it elongates a certain amount before fracture takes place. The two pieces are placed together and the amount of extension is measured against marks made before starting the test which is expressed as a percentage of the original gauge length.

PROPERTIES/COMPOSITION INDIA (IS 1786) RADHA 500 TMT BAR AMERICAN (ASTM A 615) EURO (DIN 488)
MECHANICAL PROPERTIES Grade Fe - 500 Grade Fe - 500 Grade 60 (420) Bst 500-s<
Proof Stress (Min.) 500 N/mm2 525 N/mm2 420 Mpa 500 Mpa
Tensile Strength (Min.) 545 N/mm2 600 N/mm2 620 Mpa 550 Mpa
Elongation(Min.) 12% 18% 9% 10%
Mandrel dia for bend test Upto & including 20 mm-4D Upto & including 20 mm-4D 10 to 16 mm-3.5D 6 To 12 MM-5d
over 20mm-5D over 20mm-5D 20 mm to 25mm-5D 14 To 16 MM-6d
28 mm to 32mm-7D 20 To 28 MM-6d
CHEMICAL COMPOSITION (%)
Carbon 0.30 Max. 0.25 Max. 0.30-0.40% 0.22 Max.
Sulphur 0.055 Max. 0.055 Max. 0.05 Max. 0.05 Max.
Phosphorus 0.055 Max. 0.055 Max. 0.05 Max. 0.05 Max.
S+P 0.105 Max. 0.105 Max. 0.100 Max. 0.100 Max.
PROPERTIES/COMPOSITION INDIA (IS 1786) RADHA 550 TMT BAR AMERICAN (ASTM A 615) EURO (DIN 488)
MECHANICAL PROPERTIES Grade Fe- 550 Grade Fe- 550 Grade 75 (520) Bst 500-M
Proof Stress (Min.) 550 N/mm2 570 N/mm2 520 Mpa 500 Mpa
Tensile Strength (Min.) 585 N/mm2 640 N/mm2 690 Mpa 550 Mpa
Elongation(Min.) 8% 16% 7% 8%
Mandrel dia for bend test Upto & including 20 mm-5D Upto & including 20 mm-5D 6 to 25 mm-5D 6 D
Elongation (Min.) over 20mm-6D over 20mm-6D above 20 mm-7D 8%
CHEMICAL COMPOSITION (%)
Carbon 0.30 Max. 0.25 Max. 0.30-0.40 0.022 Max.
Sulphur 0.055 Max. 0.050 Max. 0.05 Max. 0.050 Max.
Phosphorus 0.050 Max. 0.050 Max. 0.05 Max. 0.050 Max.
S+P 0.100 Max. 0.0100 Max. 0.100 Max. 0.100 Max.

UTM (Universal Testing Machine) machine (For conducting the destructive testing to measure YS, UTS and Elongation as per IS-1786:2008)

Specto meter (For testing the Chemical properties of the Raw Material)

S.NOCHEMICAL ELEMENTCONTROLLING PROPERTYACTUAL EFFECT
1Carbon (C)Hardness, strength, weldability and brittlenessHigher carbon contributes to the tensile strength of steel, resulting in higher load bearing capacity, while lower carbon content (less than 0.1% ) will reduce the strength. Higher carbon content ( 0.3% and above) makes the steel bar unweldable and brittle. As per BIS the carbon for Fe – 550 grade shall be <0.30% and Radha 550 TMT bars maintains carbon < 0.25% which is even better than the BIS norms.
2Manganese(Mn)Strength and yield strengthThe manganese content in steel is not specified as per IS:1786-2008,however higher manganese content in steel increases the tensile strength and the carbon equivalent property
3Carbon Equivalent(CE)Hardness, tensile strength and weldabilityCarbon Equivalent is the measure of the tendency of the weld to form martensite on cooling and the suffer brittle fracture. It is directly related to hydrogen induced cold cracking which is the most common weld defect for steel. Higher concentration of carbon and other alloying element tend to increase hardness and decrease weldability. As per BIS the CE shall be < 0.42% and Radha 550 TMT Bars maintains it < 0.40%

Carbon Equivalent is the measure of the tendency of the weld to form martensite on cooling and suffer brittle fracture. It is directly related to hydrogen induced cold cracking, which is the most common weld defect for steel. Higher concentration of carbon and other alloying element tend to increase the hardness and decrease the weldability. TMT process can produce the desired yield strength with steel of relatively lower carbon equivalent by adjusting the on-line heat treatment parameters.

CARBON EQUIVALENTWELDABILITY
Up to 0.35Excellent(Radha 550 TMT’s CE)
0.36-0.40Very good
0.41-0.45 Over 0.500
0.46-0.50 Fair
Over 0.500 Poor

Radha 550 TMT Bars are conforming to chemistry which strictly follows a narrow band. We maintain a very low level of carbon content leading to excellent weldability.

Radha 550 TMT Bars are made from hot rolled continuous casting billets and are subjected to microprocessor controlled thermo-mechanical treatment in following three stages:

Step 1: Quenching The hot rolled bar leaves the finishing mill stand at 1050 deg Celsius which is rapidly quenched by a special cooling process by the Thermex technology. The quenching converts the bars surface layer to martensite, which causes it to shrink. The shrinkage pressurises the core helping it to form the correct crystal structures, while the core remains hot and austenitic.

Step 2: Self Tempering The bar leaves the quench box with a temperature gradient through its cross section and as the bar cools, heat flows from the bar centre to its surface and the bar’s heat and pressure correctly tempers an intermediate ring of martensite and bainite.

Step 3: Atmospheric Cooling Finally, the slow cooling after quenching automatically tempers the austenitic core to ferrite and pearlite on the cooling bed, which now has a strong and tough, tempered martensite on the surface layer of the bar: an intermediate layer of tough martensite and bainite and a refined, ductile ferrite and pearlite core.

  • German Thermex technology, most advanced technology.
  • Hot/ cold billet charging facility.
  • Billet weighing facility.
  • High pressure water de-scaling facility-Ensures scale free TMT bars.
  • High speed continuous mill for less exposure to atmosphere which helps in maintaining close dimensional tolerance and uniform weight across the length of the bar
  • Inter stand tension control rolling MTC (Minimum Tension Control).
  • Online rapid water quenching unit for production of thermo-mechanically treated high strength Bars (TMT bars).
  • Sparkonix computer controlled notch making CNC machines for even spaced and precise depth rib cutting.

Radha 550 TMT Bars posses precise and uniform parallel rib pattern engraved through computer controlled notch making Sparkonix CNC machines which results in excellent bond strength with concrete.

Consistency of parallel rib pattern is uniform and guaranteed in each and every bar as the roll pass in finishing mill stand is not over used, thus ensuring the final product delivered to the is of extremely high quality.

Radha 550 TMT Steel Bars have Precise and uniform parallel rib design which results in superior mechanical properties as compared to the other ordinary Steel Bars in the market. Parallel Ribs on Radha 550 TMT Bars are produced with the help of Sparkonix CNC machine in state of the art high speed automated rolling mill machines which give very Close dimensional tolerance, superior surface finish, uniform & precise parallel rib pattern to the Steel Bars.

The following points give Radha 550 TMT Bars an advantage over their competitors:

Weight and length: Radha 550 TMT Bars follows strict BIS norms and are manufactured as per BIS standards promising superior strength, ductility and bendability compared to other tmt manufacturers in the same sectional properties.

Bond Strength: Radha 550 TMT Bars provides superior strength to the buildings as they posses uniform and precise parallel rib pattern, which ensures excellent bonding with concrete, resulting in stronger and more durable structure.

Dimensions: with the help of high speed rolling mill Radha 550 TMT Bars have close dimensional tolerance, superior surface finish, standard weights and precise rib pattern.

Bendability: Radha 550 TMT Bars have high elongation which means that the TMT bars are capable of absorbing large amount of energy by plastic deformation before undergoing failure by fracture, due to its good expansion capacity it holds the columns against failure during the earthquake. – a boon for ductile constructions in the seismic zones.

Weld-ability: Radha 550 TMT Bars have low carbon equivalent and is directly related to hydrogen induced cold cracking which is the most common weld defect for steel. Higher concentration of carbon and other alloying element tend to increase hardness and decrease the weld-ability.

Corrosion Resistant: Radha 550 TMT Bars have minimum or negligible residual stresses in order to prevent any chance of rusting, and also by micro-alloying, coupled with the state-of-the-art rolling technology, which imparts excellent corrosion resisting properties in the TMT bars.

Earthquake Resistance: Radha 550 TMT Bars have high UTS/YS ratio which signifies that steel is capable of elongating to a large extent when loaded beyond yield point and It is with this view that some of the international specifications stipulate fairly high values for the UTS / YS ratio.

Resistant to fatigue : Radha 550 TMT bars can withstand any dynamic loading due to their excellent strength of the surface layer. This makes Radha 550 TMT Bars a unique choice for super strong construction.

Cost Savings: Radha 550 TMT Bars have high UTS/YS ratio and high elongation which results in lesser consumption when compared to the other TMT of the same sectional properties which has low UTS/YS ratio and lesser elongation. As per studies 550 Grade TMT with high strength saves about 10-14% than the corresponding lesser strength TMT of Fe 500

Keeping all the above points in mind, Radha Smelters launched their Earthquake resistant, high quality, MAHA SHAKTISHALI Radha 550 TMT Bars which ensures high quality TMT for one of the fastest developing economy in the world.

The Steel consumption depends on the strength of the TMT Bar. Higher the strength, lower will be the consumption.

Radha 550 TMT Bars are manufactured in a world class state-of-the-art high speed rolling mill ensuring excellent yield strength which exceeds the parameters specified in the BIS standard IS-1786 resulting in material saving of approx 24% compared to the Fe 415 TMT manufactured by the secondary producers. Not only this when the quantity of steel consumption reduces you save on transportation cost, material handling cost, larger carpet area is achieved due to slimmer pillars and also reduces the overall time of construction.

Yes Radha 550 TMT Bars are sold in retail shops by pieces.

Radha 550 TMT Bars in pieces offer you the following advantages:

  • Guaranteed weight in each piece.
  • Procure exact pieces as recommended by structural engineer or architect.
  • Avoids wastages in sites as exact number of pieces is purchased.
  • Guarantees customer satisfaction by reduction in delays and reduces labour cost.

Find the following on the Bars

  • 1.Radha TMT 550 stamp on every meter of bar
  • 2.Blue Radha TMT 550 strip on every bundle and
  • Blue Radha TMT 550 tag on the material proves the genuineness of Radha 550 TMT Bars . So watch out for above 3 things while purchasing Radha 550 TMT Bars .
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