Rolling Scheme of Round–32 mm

Table 6.5 Input Billet Size-100 x 100 x 6 Mtrs

STD

Pass

H

В

t

Dc

Nrpm

1

Barrel

90

103

515

500

Tilt 90

2

Barrel

76

100

523

320

3

Barrel

66

104

523

310

4

Rd 32/40

78

76

20

425

315

5

Barrel

52

92

523

300

Tilt 90

6

Rd 32- 36

62

62

6

420

340

7

Barrel

37

75

425

335

8

Rd 32-36

46

48

8

420

315

9

Barrel

27

60

400

300

Tilt 90

10

Rd-32

41

35

6

420

300

11

Rd-32

28

46

6

370

390

12

Rd-32

32

32

3

370

500

Note: Where H and В are the size of metal in the respective passes, t is the roll gap, Dc is the collar diameter of the roll, Nrpm is the motor rpm

Roll Pass Design R-32 mm

Stand-12 (Finishing Pass)

Design of Finishing Pass

Fig. 6.10 Design of Finishing Pass.

Pass-11 (Pre-finishing Pass)

Pre-finishing Pass. 6.3 Pass-10 (Strand Pass)

Fig. 6.11 Pre-finishing Pass. 6.3 Pass-10 (Strand Pass)

Strand Pass. 6.4 Pass-8 (Rd-32-36 Pass)

Fig. 6.12 Strand Pass. 6.4 Pass-8 (Rd-32-36 Pass)

Pass-8

Fig. 6.13 Pass-8

Pass-6 (Rd-32-36 Pass)

Pass-6

Fig. 6.14 Pass-6.

Pass-4 (Rd-32-36 Pass)

Pass-4

Fig. 6.15 Pass-4.

Roll Design of Finishing Pass

Roll Diagram of Pre-finishing Pass

Roll Design of Pre-finishing Pass

Fig. 6.17 Roll Diagram of Pre-finishing Pass.

Roll Design of Strand Pass

Layout of Merchant Mill

Layout of Merchant Mill

Fig. 6.19 Layout of Merchant Mill.

Rolling of TMT Bars

TMT Bar

Fig. 6.20 TMT Bar.

TMT stands for “Thenno-Mechanically Treated” steel reinforcement bars.

Type of steel

Yield Strength MPa,min.

Tensile Strength, MPa,min.

Elongation,% min.

IS 2062 GrA

26

240

23

FE415

410

485

14.5

Process of TMT

This process has become very popular, as with the use of process of controlled cooling TMT bars system, yield strength, will have atleast 65% higher than the plain mild steel. At the sametime, bond strength will also be 100% more than the plain round bar. End hooks will no longer required.

The most important point is that though there is a remarkable increase in yield strength, but there will be no major loss of ductility; thereby TMT bars will also have good weld-ability.

The use of TMT bars has not only drastically minimized the quantity of steel requirement. If further reduce the cost of transportation, storage and handling of less quantity of steel, that is with no end hook requirement, will also facilitate easier handling with reduced cost. Laying in Site is simplified and reduces the labour charges.

We can say that TMT bars are having following advantages over the cold twisted ribbed bars:

  • • High Strength with High Ductility.
  • • High Corrosion Resistance.
  • • Very High Weld- ability.
  • • Very High Bend ability.
  • • High Strength at Elevated Temperature.
  • • Bars are Stress Free.
  • - Bars have Protective Shield.
  • - Pollution Free Process.
  • - Lower Manufacturing Cost.
  • - International Quality Products.
  • - Saving in steel.
  • - 50% Less Labour required in Mills.

Comparison of Different TMT Grades

Table 6.6

Standard

Grade

Yield Stress (min) N/mm2

UTS (min.) N/mm2

% Elongation

BIS 1786

Fe415

415

485

14.5

Fe415 D

415

500

18

Fe500

500

545

12

Fe500 D

500

565

16

Fe550

550

585

10

Fe550 D

550

600

14.5

Fe600

600

660

10

Contd...

BS 4449

B500A

500

1.05

2.5

B500B

500

1.08

5.0

B500C

500

1.15

7.5

ASTM 615M

40

280

420

11-12

60

420

620

7-8

75

520

680

6-7

The Effect of Carbon Equivalent on Weldability

Table 6.7

Carbon equivalent (CE)

Weldability

Upto 0.35

Excellent

0.36 - 0.40

Very Good

0.41-0.45

Good

0.46-0.50

Fair

Over 0.50

Poor

Rib Design

Purpose of proper rib design is to:

  • • Increase the bond with concrete.
  • • Ribs or lugs termed as deformations provide a high degree of interlocking of cements concrete and rebar.
  • • Minimum requirements for these deformations (spacing, projection, etc.), have been developed by extensive lengthy experimental research and are specified in the standards.

Control Data for Thermo Mechanically Treated Wire Rods/Bars

Table 6.8

Size

Sec

tional

Weight

kg/M

Core

Dia.

MM

Max.

Dia.

H

MM

LUGS (Transverse RIB)

RIB

Av.

Spacing

A'

between

lugs

Max.

MM

Lug

Angle

“0”

Min.

Proected

Area

MM2

DTR

Av.

Height

Min.

MM

Max.

width

b’

MM

Length

(Min.)

LTR.

MM

Thick

ness

Max.

al

MM

Width

Max

Ы

MM

8

.395

7.6

8.72

0.56

0.8

10

0.8

0.8

4.0

55

1.36

10

.617

9.5

10.90

0.70

1.0

12

1.0

1.0

5.3

55

1.70

12

.888

11.4

13.08

0.84

1.2

15

1.2

1.2

6.5

55

2.04

16

1.58

15.2

17.44

1.12

1.6

20

1.6

1.6

7.5

55

2.72

20

2.47

19.0

21.80

1.40

2.0

26

2.0

2.0

9.5

55

3.40

25

3.85

23.75

27.25

1.75

2.5

30

2.5

2.5

11.0

55

4.25

28

4.83

26.6

30.52

1.96

2.8

35

2.8

2.8

11.0

55

4.76

32

6.31

30.4

34.88

2.24

3.2

40

3.2

3.2

11.0

55

5.44

36

7.99

34.2

39.24

2.52

3.6

40

3.6

3.6

13.0

55

6.12

40

9.86

38.0

43.6

2.80

4.0

40

4.0

4.0

13.0

55

6.80

Note: As per BIS, the projected area /'.e., 0.17 x D should not be less than the value computed by the following formula based on different elements of TMT product.

i.e.,

Where,

DTR = Depth or Height of Lug (transverse Rib)

LTR = Length Lug (transverse Rib)

A = Average Spacing between two consecutive Lugs 0 = Lug Angle

• Different bar producers use different patterns, all of which should satisfy these requirements.

Roll Pass Design of TMT-32

Rolling of TMT-32 is same as rolling of plain round 32 mm, except higher metal is required to form lugs and ribs hi finishing pass. The area of finishing pass of TMT should be maintained same as that of plain round-32. Metal sizes of subsequent passes are required to be enhanced. To accommodate the metal size, the plug oval pass of Round-36 (one size higher) is taken in stand-10, instead of normal round -32 mm pass of plain round scheme.

Table 6.9 Rolling Scheme for TMT-32 MM

Input Billet Size: 100 * 100 * 6 Mtrs

STD

Pass

H

В

t

Dc

Nr

1

Barrel

 
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