Summer Internship Presentation

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Summer Internship at Sunflag Iron & steel company limited, Bhandara

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Summer Internship Presentation

  1. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 18. •High Rejection in Higher Cross-Sections, largely around 23 mm For Jan-April FOR JAN-APRIL
  19. 19. •Like 10B21, in 15B41 too, large rejection in coils around 23 mm For Jan-April FOR JAN-APRIL
  20. 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. 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. 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. 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. 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. 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. 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. 27. For May •Significant rejections around size 8mm(49/35),14mm(35/35) •& 23(29/16)mm. FOR MAY
  28. 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. 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. 30. For May Noting down the Abnormal Heat Number from the rejection trend for parameters comparison FOR MAY FOR MAY
  31. 31. For May FOR MAY FOR MAY Noting down the Abnormal Heat Number from the rejection trend for parameters comparison
  32. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 42. •Graph shows slightly higher the Mn/Ti ratio, •higher rejection were found. 10B21
  43. 43. •Graph shows as Tap-C increases, higher rejections are fo
  44. 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. 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. 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. 47. Thank You……

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