2012-Summer Internship Project Report

1. 1
Summer Industrial Training
Report-2012
Analysis of longitudinal Surface Discontinuous Cracks in Cold
Headed Quality steel grade as-rolled coils
at
Sunflag Iron & Steel Company Limited,
Bhandara Road, Maharashtra
7th May-6th July.
(Submitted in partial fulfillment of the Summer Internship-2012)
Guided by Submitted by
Mr Avinash Pansi Piyush Verma
General Manager, 09MT3018
Quality Assurance and Customer Services Metallurgical & Materials Engineering
Sunflag Iron & Steel Plant IIT, Kharagpur
Co-guided by
Mr Nitin Raut Manager
Quality Assurance and Customer Services
Sunflag Iron & Steel Plant

2. 2
Acknowledgement
I would like to thank my Guide, Mr Avinash Pansi (General Manger) and Co-Guide, Mr Nitin Raut (Manager),
Quality Assurance & Customer Services department, Sunflag Iron & Steel Plant, Bhandara Road) for their immense
support and guidance throughout my Internship at Sunflag. I would specially like to thank Mr Nitin Raut for always
giving time out of his busy schedule, whenever I approached.
I would like to thank Sunflag Steel Plant’s HR Management Department for providing me an opportunity to get
an exposure of working in an industrial environment, the problems related to manufacturing and an opportunity for 2
continuous months to meet the metallurgists working in industry.
I am thankful to Mr Sandeep Nadagouda (Assistant General Manager, Industrial Engineering & Training), for
providing me an opportunity to deliver a short lecture on “Iron-Iron carbide phase diagram” to GETs from non-
metallurgical background on 15th June, which I believe added some value to the Sunflag Organization.
Piyush Verma
28th August, 2012

3. 3
Contents
Page
1. About the Company 4
2. About the Internship 4
3. Plant Visit 4
4. Following a CHQ Grade production process 6
5. Project 7
6. Analysis 8
7. Final Conclusion 16
8. At the End of Training 17

4. 4
About the Company
Sunflag Iron & Steel Company Limited is a part of Sunflag Group of Industries. It’s an Integrated Steel
Plant, situated at Bhandara Road, Maharashtra & is in the business of manufacturing special steel and power for
22 years. The plant is located on 2.3 Sq. Km of land. Sunflag Steel has strength of around 2000 people. The
plant has present installed capacity of making 400,000 metric tonnes per year of quality special steels. Sunflag
Steel is the leading producer of Special Carbon, Alloy Steels, Micro Alloy and Stainless steels. Sunflag Steel’s
customers include all major Original Equipment Manufacturers in India, Americas, Europe, South East / Far
East / Middle East Asia.
About the Internship
 Observed the steel production process and got an overview of a steel plant, from its Sinter plant, Mini
Blast Furnace, Refining Furnaces to Rolling mills and testing.
 Worked on the Analysis of Longitudinal Discontinuous Surface cracks in Cold Headed Quality Steel
grade coils in Bar & Section Mill.
Plant Visit
1. EAF-Electric Arc Furnace-Mannesmann Demag (55 MT)
 Continuous feeding of sponge iron
 Decarburization & Dephosphorization.
 Eccentric Bottom Tapping.
Raw materials:-
Scrap – 6 Tonne
Hot Metal from MBF (Mini Blast Furnace) – 30-32 Tonne
DRI (Direct Reduced Iron)- 28-30 Tonne.
Reactions:-
C+O₂ = CO ₂
Si+O ₂ =SiO ₂
Mn+O ₂ =MnO ₂
P+O ₂ =P ₂ O5
2. LRF-1 Ladle Refining Furnace1 (55 MT)-
 Deoxidation and Desulphurization (Continuous Arcing)
 Ferro Alloys, Lime etc additions for controlling the chemistry like
 FeMn, FeSi, FeCr, FeMo, SiMn, CPC (Coke Calcined Petroleum).
 Sulphur is mainly reduced to 100-150 ppm (0.010%-0.015%)
Al+ [O] = Al ₂ O3
Si+ [O] =SiO ₂
Mn+ [O] =MnO ₂
S+ [O] =SO ₂
3. LRF-2 Ladle Refining Furnace2 (55 MT)-
 Reheating of the heat if necessary for maintaining the temperature (Continuous Arcing)

5. 5
4. Vacuum Degassing –Danieli (VD)
 To reduce dissolved gases levels like H₂ , N₂, O₂ by creating vacuum (1milliBar)
 Addition of wire rods Al (for fixing O₂) Ti (for fixing N₂), CaSi (for modifying the
 Al₂O3 inclusion into spherical C₁₂A7 (12CaO.7Al₂O3) and B wire (to achieve Hardenability
in CHQ grades)
 CHQ GRADE- 10 min VD holding time at 1mbar
5. Continuous Casting Machine (CCM)
 Laddle from VD is put in a turret (can contain at a time 2 laddle containing hot metal), from
which through shroud (made of graphite) liquid metal is poured in a T-type(to avoid
turbulence) tundish (all closed to avoid oxidation of liquid steel), from tundish, steel is
passed through already heated (to avoid thermal shock) SEN( Sub-Entry Nozzle-made of
Zr+Graphite-3 numbers per tundish).
 Casting of the liquid steel continuously in 2 X 3 stand billet caster.
 Electro Magnetic Stirrer (EMS)(600 mm from the top of the mould which is also 300 mm
from the bottom- total mould length 900 mm) to avoid dendritic structure during
solidification(Avoids macro-segregation of Pb and S).
 Hydraulic Mould (Water cooled Copper) Oscillator to avoid sticking (can produce
Oscillation hook marks later in the billets).
 Addition of Mould Flux (REDx here) to avoid friction between cast and the mould (can result
in entrapments later in rods).
6. Billet Yard
 Hot-Billet is gas-cut and air-cooled, for 2 days, then the Billet-Grinding (must for CHQ
Grades for better surface finish) takes place either manually or in Billet Grinding Machine.
 Billet-Grinding done upto 1-3mm depth removes surface oxides.
7. Reheating Furnace
 Billet is reheated upto1200˚C (Top Heating), fuel used: gases from MBF.
 For 2-3 hrs depending upon the cross-section of the billet (160X160, 130X130, 320X230).
 Discharge temperature around 1150˚C.
8. Rolling Mill
 From reheating furnace, billets are rolled in either 20 stand WRD (Wire RoD mill)
(For sizes >12mm) or 20+10 stand WRB (Wire Rod Block mill)(for sizes 5.5-12mm).
 -Morgardshammer Garret coiler (made of nodular cast iron to avoid friction between drum
and rod) used to coiling the wire rods.
9. Testing and Sampling
 In SMS (EAF+LRFs+VD) using lollypop samples (for chemistry).
 Billet cross-section chemistry, Shear-cutting at stand-8 of rolling mill and finishing stands.
 Front and back ends of each coil goes following testings /observations
 MPI (Magnetic Particle Separation method for locating defects if any)
 Under Magnifying glass for identifying various surface defects and measuring crack length.
 Under Optical Microscope
 For differentiating between continuous and discontinuous cracks.
 For measuring the decarburization depths near the cracks and concluding
whether crack formed before or during rolling.
 For locating any entrapments near cracks.
 For identifying the type of inclusion(if any near the cracks)
 For measuring the crack depth.
Crack depth (in mm)
Crack length (in mm) 0.1(20mm)

6. 6
Following a CHQ Grade production process
 Heat Number-74101 (15B25) (Continuous Arcing)
 EAF Tapping temperature-1630˚C
Additions made:-
-SiMn-600 kg
-Cao (lime)-300 kg.
 LRF-1 Starting Temperature-1561˚C (Refractory Lining- MgO -C, Magnesia-Carbon)
Additions made:-
-Al bar – 2 X 22 kg, after 3 minutes of arcing.
-CaO – 100 kg
-SiMn-250 kg
-Fe-Si-36 kg
-CPC (Coke Calcined Petroleum)-50 kg
-Al cored wires-120 meter
-FeCr HC (High Carbon)-50 kg
-Al dros (major content Al₂O3, added to refine the slag, contains SiO₂ too)
-Electrode (Length-2100 mm and diameter-500mm) (Electrode length decreases due to
erosion)
-HC FeMn 120 kg
-HC FeCr 10 kg
-CaO-50 kg
 VD (Vacuum Degassing)
P-1 millibar
For CHQ Grade-10 min holding time at 1 millibar
CaSi-strand1-61 m
Al-strand1-64 m
B-strand1-16 m
Ti-strand1-125 m
Laddle In Temperature-1669˚C
Laddle out Temperature-1600˚C
 CCM
-EMS 600mm below top surface (300 mm from bottom) of the oscillating mould
(vertically), total length of the mould-900 mm
-REDx added to avoid oxidation of liquid steel in the tundish.

7. 7
Project
 Problem: In Sunflag, significant rejections in coils are coming from CHQ grades, most of which
comprise of Boron CHQ grades (10B21, 15B25, 15B41).
Samples sent by Sunflag Customer
Micro Turner Rejected Cold Forged
 About CHQ grades:
 Cold Forged- Mainly for fasteners and similar components.
 Starting material-Wire Rods.
 Metallurgical specification:-
- Surface defect depth less than 0.5% of wire rod diameter.
- Decarburization depth less than 0.5% of wire rod diameter.
- Cold-upsetting to 85% minimum of wire rod.
 Benefits of Cold-Forging:-
- High As-forged strength.
- No trimming and scaling loss.
- Good surface finish (required for automotive components)
 Approach: Work in the project mainly included
 1st-Data Collection from the Record registers of CHQ grades for discontinuous cracks
between January-May & arranging it.
 2nd-Data Analysis of January-May-To find out which grade among Boron CHQ grades is
most problematic, and further which size(cross-section) and to look if there’s any trend.
 3rd-Identification of the “NOT OK” Heat and observing its cracks under Optical
Microscope (if available i.e. sample not thrown) and to look for any inclusion.)
 4th-Comparison of various processing parameters responsible for inclusion occurrence
of the Good Heats and the Bad Heats.

8. 8
Analysis
 January-April
NUMBER O F NTFRO NT BAC K BAC K TO TAL C O ILS C O ILS
Sr HEAT GRAD SIZ FRO %AGE %AGE
REMARK
No. NO . E E SAMPLES O K NO T O K O K NO T O KC O ILS O K NO T O K O K REJEC TIO N
C HEC KED
1 72665 10B21 5.5 44 22 0 22 0 22 22 0 OK 100 0
3 71590 10B21 6 10 5 0 4 1 5 4 1 80 20
4 71590 10B21 6 10 5 0 4 1 5 4 1 NOT OK 80 20
46 72866 10B21 7 36 18 0 18 0 18 18 0 OK 100 0
49 71806 10B21 8 10 4 1 4 1 5 3 2 NOT OK 60 40
51 71937 10B21 8 50 20 5 20 5 25 17 8 NOT OK 68 32
84 72847 10B21 9 64 0 32 0 32 32 0 32 NOT OK 0 100
85 72847 10B21 9 64 20 12 11 21 32 4 28 NOT OK 12.5 87.5
86 71590 10B21 10 14 7 0 4 3 32 4 3 NOT OK 90.7 9.3
91 72861 10B21 10 56 26 2 24 4 28 22 6 NOT OK 78.57 21.42
92 72860 10B21 12 70 35 0 35 0 35 35 0 OK 100 0
205 72670 15B25 5.5 40 18 2 20 0 20 18 2 NOT OK 90 10
206 71569 15B25 6 6 3 0 3 0 3 3 0 OK 100 0
255 72754 15B25 8 8 3 1 3 1 4 2 2 NOT OK 50 50
256 73338 15B25 8 16 4 4 5 3 8 2 6 NOT OK 25 75
257 73339 15B25 8 46 15 8 5 10 23 9 14 NOT OK 39.14 60.86
258 71597 15B25 9 4 2 0 2 0 2 2 0 OK 100 0
259 71628 15B25 9 4 1 1 2 0 23 1 1 NOT OK 95.66 4.34
260 71664 15B25 9 22 9 2 11 0 2 9 2 NOT OK 0 100
262 71569 15B25 10 16 8 0 3 5 8 3 5 NOT OK 37.5 62.5
369 72863 15B25 16 4 2 0 2 0 2 2 0 OK 100 0
370 72900 15B25 16 16 8 0 8 0 8 8 0 OK 100 0
371 72911 15B25 16 22 8 3 10 1 11 7 4 NOT OK 63.64 36.36
372 71628 15B25 17 4 1 1 2 0 8 1 1 NOT OK 87.5 12.5
373 72900 15B25 17 16 7 1 7 1 8 6 2 NOT OK 75 25
374 72827 15B25 18 30 12 3 13 2 15 12 3 NOT OK 80 20
386 71596 15B41 16 12 0 6 0 6 6 0 6 NOT OK 0 100
387 72214 15B41 16 4 1 1 2 0 2 1 1 NOT OK 50 50
388 72215 15B41 16 6 0 3 0 3 3 0 3 NOT OK 0 100
389 72215 15B41 16 6 3 0 3 0 3 3 0 OK 100 0
390 72215 15B41 16 28 11 3 14 0 14 11 3 NOT OK 78.58 21.42
391 72757 15B41 19 14 7 0 7 0 7 7 0 OK 100 0
406 71776 15B41 24 14 7 0 5 2 7 5 2 NOT OK 71.43 28.57
407 71776 15B41 25 42 12 9 11 10 7 4 3 NOT OK 57.15 42.85
408 73280 15B41 25 40 18 2 15 5 20 13 7 OK 65 35
409 73280 15B41 25 6 0 3 0 3 3 0 3 NOT OK 0 100
410 73279 15B41 26 20 8 2 7 3 10 6 4 NOT OK 60 40
411 73279 15B41 26 2 1 0 1 0 1 1 0 OK 100 0
(Total Data for January-April includes observation of 411 entries-All not shown)

9. 9
 Population Grade Vs Size Vs Rejection (January-April)
GRADE SIZE Total Coils Coils % Rejection
Coils Checked OK NOT OK
10B21 5.5 70 70 0 0
6 479 446 33 6.88
6.5 40 39 1 2.5
6.7 167 163 4 2.39
7 107 104 3 2.8
8 82 58 24 29.26
13.3 7 5 2 28.57
15 9 6 3 33.33
16 7 7 0 0
16.3 3 3 0 0
17 11 11 0 0
18 4 2 2 50
19 11 11 0 0
20 7 5 2 28.57
21 75 45 30 40
23 22 10 12 54.54
24 79 25 54 68.35
26 30 21 9 30
28.5 84 29 55 65.47
15B25 5.5 87 65 22 25.28
6 80 61 19 23.75
6.7 76 75 1 1.31
8 219 154 65 29.68
9 12 5 7 58.33
10 114 85 29 25.43
11 130 112 18 13.84
12 47 43 4 8.51
13 672 531 141 20.98
14 37 1 36 97.29
15 216 162 54 25
16 26 21 5 19.23
16.3 265 205 60 22.64
17.3 10 7 3 30
18 22 19 3 13.63
18.3 33 27 6 18.18
23 7 3 4 57.14
15B35 18.3 1 0 1 100
15B41 14 7 6 1 14.28
16.3 49 34 15 30.61
19 7 7 0 0
20 48 42 6 12.5
23 47 37 10 21.27
24 24 19 5 20.83
25 20 3 17 85

10. 10
 Population Curves
500
10B21, Coils Checked Vs Rejected
6
450
400
Number of Coils
Coils Checked
350
300
8.5
250
200
150 6.7
9 9
100 7 10
5.5 8 21 24 28.5
50 6.5 24 28.5
6 8 12 21 23 26
0 5.56.5 8.5 10
6.77 13.3
13.3 15 16 17 18 19 20
12 16.3 16.3 23
15 16 17 18 19 20 26
0 5 10 15 20 25 30
Size (in mm)
700
15B25, Coils Checked Vs Rejected
13 Coils Checked
600
Number of Coils
500 Coils Not OK
400
300
16.3
200 8 15
13
100 10 11
5.5 6.7 8
6 16.3
14 15 16
0 5.5 6.7
6 9 10 11 12
12
18.3
18
16 17.318.3
18 23
0 5 10 15 20 25
Size (in mm)
15B41, Coils Checked Vs Rejected
60
50
Numbe of Coils
16.3 20 23
40
30
Coils Checked
24
20 25 Coils Not OK
16.3 25
10 23 Полиномиальная (Coils Not OK)
14 1920 24
0 14 19 26
0 5 10 15 20 25 30
Size (in mm)

11. 11
 Grade-Size-Rejection Trend
Higher Rejection Trend in
10B21 % Coils Rejection Cross-section around
23mm
100
9
80
% Rejection
24 28.5
60
18 23
40 21
8 13.3 15 20 26
20
0
6 6.7
7
5.56.5 8.5 10 12 16 17
16.3 19
0 5 10 15 20 25 30
Size (in mm)
15B25 % Coils Rejection
100 14
90
80
70
% Rejection
60 9 23
50
40
30 8 17.3
5.5
6 10 13 15 16.3
20 16 18.3
10 11 18
12
0 6.7
0 5 10 15 20 25
Size (in mm)
15B41 % Coils Rejection
100
90
25
80
70
% Rejection
60
50
40
30 16.3
20 23 24
14 20
10
0 19 26
0 5 10 15 20 25 30
Size (in mm)

12. 12
 All Grade Vs Size Analysis
Grade-wise Rejection in coils in different sizes
Common
100
Rejection of
around 60% for
90
14-15B25 10B21,15B25,15B4
Higher Rejection in
80
10B21, 15B25 around
size at 9-10 mm
70
15B25
60
% Rejection
50
15B41
40
30
Полин
20
омиал
ьная
10 (10B21
)
0
0 5 10 15 20 25 30
Size (in mm)
 May
GRADE SIZE TOTAL COILS COILS REJECTED %REJECTED
10B21 5.5 217 7 3.22
10B21 6 39 18 46.15
10B21 6.5 58 24 41.37
10B21 6.7 45 16 35.55
10B21 8 148 54 36.48
10B21 8.5 160 8 5
10B21 10 145 9 6.2
10B21 12 8 0 0
10B21 13.3 7 2 28.57
10B21 15 15 2 13.33
10B21 18.4 4 0 0
10B21 20 29 8 27.58
10B21 21 11 4 36.36
10B21 23 35 3 8.57
10B21 23.5 35 2 5.71
10B21 24 38 16 42.1
10B21 26 13 7 53.84
10B21 27.5 7 5 71.42
10B21 28.5 52 38 73.07

13. 13
GRADE SIZE TOTAL COILS COILS REJECTED %REJECTED
15B25 5.5 22 3 13.63
15B25 6.7 14 6 42.85
15B25 8 49 35 71.42
15B25 8.5 126 5 3.96
15B25 10 218 3 1.37
15B25 12 179 52 29.05
15B25 20 23 0 0
15B25 21 2 0 0
15B25 23 29 16 55.17
15B41 10 12 2 16.67
15B41 12 14 0 0
15B41 13 108 12 11.11
15B41 14 3 1 33.33
15B41 15 6 1 16.67
15B41 17 36 0 0
15B41 17.3 5 3 60
15B41 20 9 3 33.33
15B41 21 58 3 5.17
15B41 23 48 1 2.08
15B41 24 19 10 52.63
10B21 % Coils Rejection
100 Again in MAY month, high
90 rejection trend in Higher
80
70 28.5
27.5
% Rejection
60
50 6 6.5 26
40 24
6.7 8 21
30 13.3 20
20
10 15
8.5 10 23
23.5
0 5.5 12 18.4
0 5 10 15 20 25 30
Size (in mm)

14. 14
15B25 % Coils Rejection
100 14
90
80
70 8
% Rejection
60
23
50
40 6.7
30 12
20 18.3
10 5.5
13
8.5 10
0 17.3
18 20 21
0 5 10 15 20 25
Size (in mm)
15B41 % Coils Rejection
100
90
80
70
% Rejection
60 17.3
50 24
40
30 14 20
20
10 15
10 13 40
21 23
0 12 17
0 5 10 15 20 25 30 35 40 45
Size (in mm)

15. 15
 Observations
 Observed, measured and compared the depth of discontinuous surface cracks between samples
from stand 8 and the finishing stand 18th, of grade 10B21 (Heat Number-74313), using
magnifier.
-Crack depth decreased between stands 8th & 18th.
Left: Discontinuous crack (depth 0.8mm)
Right: Continuous crack (depth 0.7mm)
 Observed the distribution of discontinuous cracks on both the samples under MPI (Magnetic
Particle Inspection).
-Discontinuous cracks formed, along with few continuous cracks, all over the surface
(Not on any specific side).
 Observed the surface cracks under Optical Microscope (100x) for the inclusion pattern, by
polishing the sample along the crack.
-Of the few samples which were observed, most of the cracks where regular shaped,
indicating rolling problem.
-One of the cracks showed Alumina pattern.
Heat number-72828
Grade-15B25
Diameter- 11mm
Rejection-(rejected coils/total coils)-(2/14)
Rejection-14.28%
Crack type-Discontinuous
Crack depth-0.1mm
Crack pattern resembles
Alumina pattern

16. 16
Heat Number-72911
Grade-15B25
Diameter-15mm
Rejection-(rejected coils/total coils)-(7/24)
Rejection-29.16 %
Crack type-Discontinuous
Crack shape is regular,
(Rolling-Crack)
No inclusion found
Heat Number-72846
Grade-10B21
Diameter-9 mm
Rejection-(rejected coils/total coils)-
(66/66)
Rejection- 100%
Crack type-Discontinuous Crack shape is
regular,
(Rolling-Crack)
No inclusion found
Final Conclusion
 High rejection around 23-26mm, significantly that of 10B21
 10B21 most sensitive to surface cracks, next 15B25 & lastly 15B41.
(Increasing rejection trend with cross-section clearly seen for 10B21, from the data.)
 Higher Cross Section gets rejected more because “Crack-Depth” is larger in larger cross-section as
compared to lower cross-section, as depth gets decreased during plastic deformation, so the
acceptability depth of cracks in lower cross-section is mostly not crossed.(Generally for
Rolling Mill-Cracks, without inclusions)
 Cracks in lower-cross-section can occur by inclusions(or entrapments), as crack depths don’t get
reduced even after plastic deformation ( Alumina inclusion found in 15B25, 11mm)
 Some coils with good surface finish may get rejected if crack opens in UPSETTING, due to more
hardenability.
 Problems may be coming from rolling mill largely, as per the metallurgists at QC told, “Full-
Decarb” is generally not found around observed cracks.
 Almost every billet of CHQ was billet-grinded, and data from auto & manual mode of billet-
grinding, showed no-effect.

17. 17
At the End of Training
 Got the necessary steel industry exposure for 2 continuous months.
 Got the opportunity to closely observe the steel manufacturing processes and to relate it to the
theories studied.
 Met with different metallurgists of different departments ( from Mini Blast Furnace-MBF, SMS ,
CCM to Rolling and lastly the Quality Department), which highly enriched our experience.
 Realized the importance and role of the “Demand-Quality-Plan-Production-Supply” chain in
connection to Industry & its Customers, as from my daily visit in the “Quality Assurance &
Customer Services Department-(QA-CS)”.
 As the training period was of just 2 months, coupled with no prior industrial experience & lack of
research facilities at Sunflag and related provisions, an “EXTENSIVE PRACTICAL
STUDY” could not be met, which would have definitely put some more light over the CHQ
problem.