Summer Internship at Sunflag Iron & steel company limited, Bhandara

1. SUMMER INDUSTRIAL TRAINING
MAY-JUNE 2012
7-05-12 to 6-06-12
AT
SUNFLAG IRON AND STEEL COMPANY LIMITED,
BHANDARA ROAD, MAHARASHTRA
PIYUSH VERMA
09MT3018
INDIAN INSTITUTE OF TECHOLOGY, KHARAGPUR

2.  Worked on the project “Analysis of Surface Cracks
in CHQ (Cold Headed Quality) grades of steel ”
occurred during JANUARY-MAY 2012 .
 Observed closely the production process of CHQ coils
at Sunflag, for 2 months (8 weeks).
HOD
QA & CS
Mr N Parikh
GM (QA & CS)
& Project Guide
Mr A N Pansi
Certification

3. I would like to thank
Mr Parikh, Mr Pansi & Mr Nitin Raut (Quality
Control & Customer Services) for always taking
time out of their busy schedule, valuable guidance-
suggestions and consistent support.
Thank You Sir…..

4. About the project
 Worked under the supervision of Mr A. N. Pansi (GM-
Quality Control & Customer Services
Department), Sunflag Iron & Steel Company.
 CHQ Grades- Cold Headed Quality, grades whose
coils are cold forged (by the Sunflag Customers) to
make fasteners.
 Analysis concentrated to the CHQ grades containing
Boron (added to achieve Hardenability) mainly:-
 10B21
 15B25
 15B41

5.  In Sunflag, significant rejections in coils are coming from
CHQ grades, most of which comprise of Boron CHQ
grades (10B21,15B25,15B41).
 Work in the project mainly included
 1st-Arranging various data for January to May and
differentiating the data for Continuous and Discontinuous
cracks
 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.
 Identification of the “NOT OK” Heat and observing its cracks
under Optical Microscope (if available i.e. sample not thrown)
 Comparison of various processing parameters of the Good
Customer rejected
cold-forged sample
Crack

6. The Project
A. About Forging steels:
 Types of Forging
 Hot Forging -Done above 1200˚C
 Warm Forging - 650˚-750˚C
 Cold Forging - Room temperature.
 Popular Forging Products: Gears, Axles,
Crankshafts, Connecting Rods, Pinions, Crown
wheels.
 Major Category of Forging steels
1. Plain C
2. Plain Cr
3. C-Mn
4. Cr-Mn
5. Cr-Mo
6. Cr-Mo-Ni

7.  Grades studied in the project were of:-
10B21- Plain C steel with 0.21% average C (in as-rolled
condition)
15B25- C along with Mn, 0.25% average C (in as-rolled
condition)
15B41- C along with Mn, 0.41% average C (in as-rolled
condition)
 Final product to customers-As-rolled (Air-cooled)
CHQ wire rods, which will be cold-forged as
fasteners.
15B25
Indicates Boron Grade
For C
For Mn
Average C

8. 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.

9. Processing route
 EAF-Electric Arc Furnace-Mannesmann
Demag(55 MT)
-Continuous feeding of sponge iron
-Decarburization & Dephosphorization.
-Eccentric Bottom Tapping.
1. Raw materials:-
• Scrap – 6 Tonne
• Hot Metal from MBF(Mini Blast Furnace) – 30-32 Tonne
• DRI (Direct Reduced Iron)- 28-30 Tonne.
2. Reactions:-
C+O₂ = CO ₂
Si+O ₂ =SiO ₂
Mn+O ₂ =MnO ₂
P+O ₂ =P ₂ O5

10.  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
 LRF-2 Ladle Refining Furnace2 (55 MT)-
- Reheating of the heat if necessary for maintaining the
temperature (Continuous Arcing)
 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 Al ₂ O3 inclusion into spherical C₁₂A7
(12CaO.7 Al ₂ O3)
and B wire ( to achieve Hardenability in CHQ grades)

11.  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

12.  Billet Yard
- Hot-Billet is gas-cut and air-cooled, generally 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.
 Reheating Furnace
- Billet is reheated upto 1200˚C(Top Heating), fuel used are
gases from MBF (Mini Blast Furnace)
- For 2-3 hrs depending upon the cross-section of the billet
(160X160, 130X130, 320X230).
- Discharge temperature around 1150˚C.
 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

13.  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 the 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.
0.1(20mm) Crack length(in mm)
Crack depth(in mm)

14. Complete Observation of a Heat
 Heat Number-74101 (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

15.  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.

16. Project Work
 Collection of Data in Excel from registers of the
surface rejections of CHQ grades in Jan-April, in
tabular form.
NUMBER OFFRONT FRONT BACK BACKTOTAL COILSCOILS COILS %AGE %AGE
SAMPLES CHECKEDOK NOT OK OK NOT OK OK NOT OK OK REJECTIO
( F & B )
1 72665 10B21 5.5 LIVE WIRE 44 22 0 22 0 22 22 0 OK 100 0
2 72666 10B21 5.5 HITECH 96 48 0 48 0 48 48 0 OK 100 0
3 71590 10B21 6 10 5 0 4 1 5 4 1 80 20
4 71590 10B21 6 MICRO TURNER 10 5 0 4 1 5 4 1 NOT OK 80 20
5 71590 10B21 6 10 5 0 5 0 5 5 0 OK 100 0
6 71919 10B21 6 42 21 0 21 0 21 21 0 OK 100 0
7 71919 10B21 6 LIVE WIRE 42 21 0 21 0 21 21 0 OK 100 0
8 71920 10B21 6 66 33 0 33 0 33 33 0 OK 100 0
9 71920 10B21 6 HITECH FERROUS 66 33 0 33 0 33 33 0 OK 100 0
10 71921 10B21 6 38 38 0 38 0 38 38 0 OK 100 0
11 71921 10B21 6 34 17 0 17 0 17 17 0 OK 100 0
12 71921 10B21 6 LIVE WIRE 34 17 0 17 0 17 17 0 OK 100 0
13 71921 10B21 6 LIVE WIRE 38 19 0 19 0 19 19 0 OK 100 0
14 71933 10B21 6 68 0 34 0 34 34 34 0 OK 100 0
15 71933 10B21 6 HITECH FERROUS 68 29 5 33 1 34 29 5 NOT OK 85.294118 14.705882
16 72245 10B21 6 MICRO TURN 30 14 1 11 4 15 9 6 NOT OK 60 40
17 72548 10B21 6 HITECH 68 34 0 34 0 34 34 0 OK 100 0
18 72549 10B21 6 HITECH 66 33 0 33 0 33 33 0 OK 100 0
19 72552 10B21 6 HITECH 2 1 0 1 0 1 1 0 OK 100 0
20 72552 10B21 6 HITECH 62 31 0 31 0 31 31 0 OK 100 0
21 72553 10B21 6 LIVE WIRE 62 30 1 30 1 31 29 2 NOT OK 93.548387 6.4516129
22 73348 10B21 6 HITECH 46 19 4 15 8 23 13 10 NOT OK 56.521739 43.478261
REMARKSr No.
HEAT
NO.
GRADE SIZE
CUSTO
MER
Data for Jan-April (only some part is shown of entire data)

17. 1. Analyzed the rejections (for discontinuous
cracks only, as continuous cracks were rare) in
different Grades as per different sizes(cross-
section)(for 10B21,15B25,15B41)

18. •High Rejection in Higher Cross-Sections, largely around
23 mm
For Jan-April
FOR JAN-APRIL

19. •Like 10B21, in 15B41 too, large rejection in coils around 23 mm
For Jan-April
FOR JAN-APRIL

20. •Though the number of coils checked for 15B41 were less,
•still the trend of higher rejections in higher cross-sections of around
•is significant and similar to trend in 10B21 & 15B25
For Jan-April
FOR JAN-APRIL

21. For Jan-April
•Common (>55)% of rejections in grades 10B21,15B25 & 15B41
•at size around 23mm, also around 9-10 mm and around 14-15mm
FOR JAN-APRIL

22. 2. Analyzed the rejection trend of heat numbers for
all the grades(10B21,15B25,15B41) separately
and noted down the Abnormal Heat Number.

23. •Abnormal Heats of 10B21-71919,71953,72405,72406
For Jan-April
FOR JAN-APRIL
Noting down the Abnormal Heat Number from the rejection trend for
parameters comparison

24. For Jan-April
•Abnormal Heats of 10B21-71224,71569,72570,71664
FOR JAN-APRIL
Noting down the Abnormal Heat Number from the rejection trend for
parameters comparison

25. For Jan-April
•Abnormal Heats of 15B41-71596,72215,72560,72756,73280
FOR JAN-APRIL
Noting down the Abnormal Heat Number from the rejection trend for
parameters comparison

26. Similar Data Analysis for one month
(May)
For May
•Increasing trend of rejection in higher cross-sections of size
•around 23-28mm like in Jan-April 10B21 rejection trend.
FOR MAY

27. For May
•Significant rejections around size 8mm(49/35),14mm(35/35)
•& 23(29/16)mm.
FOR MAY

28. For May
•Again higher rejection in size 17.3(5/3), 24 mm(19/10),
•though less rejection this time in 23mm(48/1)
FOR MAY

29. •Common % of rejections(around 50%) in grades 10B21,15B25 &
•though different higher rejections are there in different grades
•but for different sizes.
FOR MAY
For May

30. For May Noting down the Abnormal Heat Number from the rejection trend for
parameters comparison
FOR MAY
FOR
MAY

31. For May
FOR MAY
FOR MAY
Noting down the Abnormal Heat Number from the rejection trend for
parameters comparison

32. 3. Observed the surface cracks of some coils
sample:-
a) MPI to observe any trend in crack distribution over the
surface.
& Under Optical Microscope for:-
b) Crack-Type (discontinuous or continuous) (before etching)
c) Crack-Depth (minor seam or deeper) (before etching)
d) Inclusion-Type (oxide, alumina, sulfide, or silicate) (before
etching)(along the crack)
e) Microstructure (after etching).
Magnifying Glass
Disc Polisher
Doing MPI

33. Sample Cut after Rolling Stand-Sample Cut after Rolling Stand-8
(Observing under Magnifying Glass)
Heat Number-74313
Grade-10B21
MPI to determine
discontinuous or continuous

34. MINOR DISCONTINUOUS CRACKS
Billet Number-8
CONTINUOUS CRACK
Billet Number-8
Observation
•Minor
seams(discontinuous
cracks) becomes few
after further plastic
deformation.
•Continuous cracks
remained though depth
decreased( from
0.1mm to 0.3 mm)
65 mm in diameter after stand 8

35. Heat number-72828
Grade-15B25
Diameter- 11mm
Crack depth- 0.1mm
Sample cut & polished along the
transverse direction
Sample cut in transverse direction but polishe
along the crack direction
Pattern resembled
Alumina inclusion
Rejection-(rejected coils/total coils)-(2/14)
Rejection-14.28%
Crack type-Discontinuous
At 100 X

36. Heat number-72828
Grade-15B25
Diameter- 11mm
No Decarburization around crack
(as if , was decarburized then it should have been white)
Alumina Crack formed after rolling.
Bainitic structure
At 100 X

37. Heat Number-72819
Grade-15B25
Diameter-16.3 mm
Surface defect observed-Minor Fin
(Not a problem, can be removed after grinding)
Fin-Length-0.12mm
No inclusion found

38. Heat Number-72911
Grade-15B25
Diameter-15mm
Rejection-(rejected coils/total coils)-(7/24)
Rejection-29.16 %
Crack type-Discontinuous
At 100 X
Crack shape is regular,
(Rolling-Crack)
No inclusion found

39. 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
At 100 X

40. 4. Compared various parameters of Good Vs Bad
Heats:-
a) FRT-Furnace Residence Time
b) Billet Grinding-%Auto & %Manual
c) Billet Chemistry
d) Average Casting Speed near end of casting (assumed
as rejections in last billets of certain heats , if in
sequence with grades of slightly different chemistry)
can result in rejections.
e) Casting Temperature.
f) VD hold-time.
g) EAF Tap C

41.  Mn/Ti ratio- As more the Mn, it may influence the
enhancement of segregation of impurities(example-P) at the
grain-boundaries (Steel Heat Treatment Handbook).
 Mn is austenite while Ti is ferrite stabilizer, also Ti doesn‟t get
dissolves in Austenite, whereas Mn does. (Steel Heat
Treatment Handbook).
 Cracks generation can be related to it. (But inclusions are not
found and generally not of phosphorus-Contradictory)
γ-Stabilizer
S.NO HEAT SIZE%REJECTIONTAP C Mn P Si Al Ti Sum Mn/Ti
1 73320 8 0 0.09 1.04 0.016 0.07 0.047 0.052 0.185 5.621622
2 73347 8 0 0.03 1.02 0.009 0.1 0.025 0.037 0.171 5.964912
3 72603 6.7 11.11 0.06 1.01 0.015 0.11 0.026 0.035 0.186 5.430108
4 73348 6 47 0.05 1.01 0.011 0.1 0.03 0.038 0.179 5.642458
5 73174 28.5 75 0.04 1.04 0.013 0.07 0.035 0.079 0.197 5.279188
6 73173 26 79 0.08 1.03 0.012 0.07 0.035 0.034 0.151 6.821192
7 71806 21 100 0.07 1 0.012 0.06 0.022 0.027 0.121 8.264463
8 71918 21 100 0.095 1.01 0.017 0.11 0.027 0.027 0.181 5.58011
9 73370 8 100 0.04 1.05 0.009 0.07 0.034 0.032 0.145 7.241379
Ferrite Stabilizers
Comparing Mn/Ti ratio Vs % Rejection
(Mn-Austenite stabilizer and Ti-Ferrite
stabilizer).

42. •Graph shows slightly higher the Mn/Ti ratio,
•higher rejection were found.
10B21

43. •Graph shows as Tap-C increases, higher rejections are fo

44. Inference
 Most of the rejections, in CHQ coils, for discontinuous
cracks, comes from size between 23-26mm.
 This „Rejection Range‟ is almost similar for all 3 grades.
 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 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)

45.  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.

46. At the end of the 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
and related provisions, an “EXTENSIVE PRACTICAL
STUDY” could not be met, which would have definitely put
some more light over the CHQ problem.

47. Thank
You……