1. Development of High Strength TMT Rebars at JSW Steel, Dolvi
Subhasis Chakrabarty, B Mrityunjay Kumar, Neel Kant, Srimanta Sam, Pradip Patra.
JSW Steel Dolvi Works Ltd

2. Key Feature JSW TMT Bars
JSW Steel TMT bars are branded as JSW NEOSTEEL
These bars are manufactured through primary production process to ensure purity and superior quality
The state of art and technical advanced bar rod mills for production are supplied from Danieli, Italy. 
JSW NEOSTEEL is toughened high strength HYQST (High Yield Quenched and Self Tempered) TMT Bar.
JSW Neosteel conforms to Indian, American, British and Australian Standards
Manufactured in Fe-500 & Fe-500D grade, Fe - 550D, Fe and CRS grade. 

3. First choice for all major infrastructure projects in the country
Delhi, Jaipur, Hyderabad, Bangalore and Chennai Metro Rail.

4. Delhi & Mumbai International Airport
Jaypee’s Yamuna Expressway
Delhi & Mumbai International Airport

5. JSW Bar Mill Dolvi Plant Characteristics
Technology – Danieli Morgardshammar
Commissioned -December 2015
Mill capacity-1.4 MTPA
Roughing (4H+4V), Pre-finishing (3H+2V+1H) & 8 NTM/FFB; Total 22 stands.
Asia’s first high speed bar mill 45 m/sec
Production Rate: 245 TPH
Product Range: 8,10,12,16,20,25,28,32,36 and 40 mm
Length of cooling bed is 102 meters. 5

6. Manufacturing Process of High Strength TMT Bar
Manufacturing process of TMT bars can be better described as “Hot Rolling” where heated iron billets continuously pass through the rollers of decreasing diameter.
After coming out of the last rolling mill bars are water cooled in a microcontroller controlled WATER BOX where temperature gradient is produced in from core to surface.
After the intensive cooling, the bar is exposed to air and the core re-heats the quenched surface layer by conduction, therefore tempering the external martensite.
When the bars are taken out of the cooling system, the heat flows from the core to the outer surface, further tempering of the bars, which helps them attain a higher yield strength.

7. Quenching and Self Tempering (QST) processB B
Quenching C
Self Tempering
Core Formation

8. Philosophy for High Strength TMT Bar
Uniform heating of Billet at Reheating Furnace at Deg C to ensure Std. 1 entry temp Deg C.
Billet rolled in particular section in mill.
After rolling temp is about Deg C before entering water box.
Temperature at cooling bed maintained about Deg. C.
Water flow and pressure kept accordingly.

9. Rolling Parameter for High Strength TMT Bar
Section (mm)
Mill Speed(m/s)
Stand #1 entry temp.(Deg C)
Water Box entry temp.(Deg C)
Cooling bed entry temp. (Deg C)
FLOW (M3/h)
PRESSURE (Bar)
RB 8 45
500 9
RB 10
850 10
RB 12
44.37
1350
12.5
RB 16
24.96
1200 14
RB 20
15.97
RB 25
20.44
1800
RB 28
16.3 11
RB 32
12.48
2000
RB 36
9.86
RB 40
7.99
1700

10. Ishikawa Diagram of TMT rebar Quality

11. Influence of Process Parameters on Microstructure
Sample (I)
Sample (II)
Sample (III)
High Yield Strength
Normal Yield Strength
Low Yield Strength

12. Influence of Process Parameters on Microstructure Continued......
Sample (III)
Sample (I)
Centre
Tempered Martensite
Centre
Tempered Martensite

13. Influence of Microstructure on Mechanical Property

14. Influence of Microstructure on Mechanical Property Continued......
Sample
YS(MPa)
UTS(MPa)
% Elongation
Martensite Ring Length (in micron)
Martensite Area (mm²)
Ferrite + Pearlite Area(mm²) I
1003
1096
16.1
827
30.3
19.9 II
819
1054
9.7
1002
31.4
18.8
III
663
745
17.7
998
18.9 IV
600
710
22.7
723
29.7
20.6 V
573
680
20.9
657
29.2
21.0 VI
538
649
22.5
660
29.3
VII
494
594 25
563
28.7
21.6
456
431
27.8
22.4 IX
470
581
23.8
383
27.5

15. Experimental results & Conclusion
Present study is helpful to optimize the process parameters to achieve mechanical property with desired microstructure.
Rolling speed and the water flow rate totally changes the microstructure as a result mechanical property.
Future aspect is to recommend industries for developing rebar of higher properties without modifying the chemical composition by optimizing the mill process parameters.

16. Draft has been generated.
Existing Grades of TMT certified by BIS
Proposal has been sent to BIS to include high strength grades Fe650 & Fe 700.
Draft has been generated.
Chemical Composition
Grades
Fe415
Fe415D
Fe415S
Fe500
Fe500D
Fe500S
Fe550
Fe550D
Fe600
%C max
0.30
0.25
%S max
0.06
0.045
0.055
0.04
%P max
0.05
%(S+P) max
0.110
0.085
0.105
0.075
0.100
%N max
0.012
%(Nb+V+Ti+B) max
CE(for MA steel) max
0.53
CE= (C+Mn/6) max
0.42
Mechanical Property
Grades
Fe415
Fe415D
Fe415S
Fe500
Fe500D
Fe500S
Fe550
Fe550D
Fe600
0.2PS / YS Mpa min
415
500
550
600
0.2PS / YS Mpa max -
540
625
UTS Mpa min
485
545
565
585
660
TS/YS ratio min
1.1
1.12
1.25
1.08
1.10
1.06
%El min (GL=5.65√A)
14.5 18 20 12 16 10
maximum force 5 8

17. Proposed Draft Standard of IS 1786
Chemical Composition
Grades
Fe 650
Fe 700
Carbon
0.32
Sulphur
0.04
Phosphorous
Sulphur and Phosphorous
0.075
Carbon Equivalent -
Mechanical Property
Grades
Fe 650
Fe 700
0.2PS / YS Mpa min
650
700
0.2PS / YS Mpa max -
UTS Mpa min
≥ 1.06(but min. TS 700 N/mm2)
≥ 1.06(but min. TS 770 N/mm2)
TS/YS ratio min 10
%El min (GL=5.65√A)

19. Thank You