1435551559625-Wheel Casting & Furnace Management.pdf

The casting process involves pouring molten metal into a mold, where it cools and solidifies into the desired shape. This process is widely used for manufacturing complex shapes and large components like rail wheels.

1. Wheel Casting

2. Introduction
•IR mfgs. Cast Steel Bogies & wheels
–CASNUB bogies at CLW
–Cast wheels for Wagons & Coaches
•Rail Wheel Factory (RWF) at Bangalore
–Capacity 1.2 lac/ annum – prodn. 2lac/annum!
–TOT from Griffin of USA
•Rail Wheel plant (RWP) at Bela, Patna
–Capacity 1.0 lac/ anum – new set up
•Copy of RWF
•Demand of wheel > 3lacs/ annum
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3. Cast Steel Wheels
•Special Parabolic profile
•Very low P & S content
•Fine equiaxed grained structure
•High yield to tensile ratio resulting from
–Specially designed heat treatment process
•Round shaped non-metallic inclusions
•IR Specification R – 19 / 1993 Pt-III
–Both for Carriage & Wagon Wheels

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4. 29/06/2015 4
Cast Steel Wheels
•Metallurgically forging route better than
casting
•Special technique of controlled pressure
casting
–Equivalent to forging route, even better
•Cross dendritic structure
–Barrier to dislocation movement
•Stipulated Mech. properties are well met

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Cast Vs. Forged Wheels
•High rate of production with uniform Quality
•Eliminates machining, any plate design
•Internal defect position is known
–So, very easy to ensure soundness
•Cleanliness by refining of steel in EAF
• Unique deoxidation ensures globulized
alumina
–These helps in achieving K
1C value
•High K
1C value
–Resistance against catastrophic failure in service

6. Chemistry of Cast Wheel
Elements Wagon wheels (BOXN) Coaching Wheels
Carbon 0.57% to 0.67% 0.47% to 0.57%
Mn 0.6% to 0.8% 0.6% to 0.8%
Si 0.15% to 0.70% 0.15% to 0.70%
S 0.03% Max 0.03% Max
P 0.03% Max 0.03% Max
Cr 0.15% Max 0.15% Max
Mo 0.06% Max 0.06% Max
Ni 0.25% Max 0.25% Max
Cr + Mo +
Ni
0.40 Max 0.40 Max
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7. CASTING & HEAT TREATMENT
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8. Liq. Steel from EAF
•Mainly Railway scraps melted in EAF
•Chemistry adjusted to reqd. spec.
•Temperature raised to required level
–1680
0
C – 1690
0
C for coaching wheel
–1690
0
C – 1700
0
C for wagon wheel (BOXN)
•Tapped in preheated ladle
•Nominal capacity 20 MT
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9. Tapping from EAF

10. Mould Blank

11. Cope

12. Drag

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Wheel Casting
•Major slag is removed from the top of ladle
•Ladle placed in ‘JOHN MOHR’ Pit
•Al. star thrust into as final deoxidiser
•Sample taken for Chemical Analysis & H
2
•Top cover with Silimenite tube sits on top
•Graphite Mould sits on the top of tube
•Pit pressurised by air to lift the liq. Metal
•Liq. Metal flow to the mould to fill cavity

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Wheel Casting Contd…
•Plunger brought down to seal the gating
•Mould placed on conveyor, next one in
•Stripping after pre-determined time
– to take away the Risers along with top
•Wheels placed on conveyor to tunnel
•Moulds go back for cleaning and recycling
•Sprue Wash, Stamping & Hub Cutting

15. Slag Off Station

16. Placing at John Mohr Pit

17. Cope & Drag Assembly

18. Mould Cavity Filling

19. Wheel Parting from Mould

20. Hot Wheel Kiln

21. Sprue Washing/Grinding

22. Hub Cutting

23. Heat Treatment
•Placed to Moving Bed Normalising
Furnace
•700
0
C→1000
0
C→960
0
C→960
0
C→960
0
C
• Followed by Rim Quenching
•Water jet on rim for 4-5 min.
•Tempering in Draw fce. at 500
0
C for 2hrs
• Hub Quenching in 3 stages, 40 sec each
•Air cooling to RT
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Wheel Inspection
•Apex grinding
•Shot blasting to clean
•Hardness Testing
•Visual Inspection in normal light
•Magnaflux Test for surface & sub-surface
under UV light, mainly for cracks
•Wheels with removable defect sent for defect
removal through grinding & rechecking

25. Magnetic Particle Testing

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Wheel Inspection Contd…
•Automated Multi probe UT in Sprue area
•Final Hub boring
•Final shot blasting
•Warpage checking
•Final Dimensional checking
•Closure test, Mech. test & BHN mapping
•1 in 500 for Coach wheels
–1 in 1000 for BOXN wheels

27. Ultrasonic Testing

28. Wheel Routing

29. Defect Codification
•Codes for some common defects
10 - Cracks
12 - Ceramic, Metal refractory
13 - Slag
15 - Pinholes
16 - Ultrasonic
32 - Gouged hub bore
35 - Gouged riser
46 – Pock holes
51 - Lap
62 - Mould inclusions

30. 10 - Crack

31. 12 – Metal Refractory

32. 13 – Slag Inclusion

33. 15 - Pinhole

34. 51 - Lap

35. 32 – Gouged Bore

36. 47 – Pocker Holes

37. 62 – Mould inclusion

38. Defect Removal

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RWF & Wheel Production.
•Producing both BOXN & Carriage wheels
•Production target this year is 2 lacs
–Against rated capacity of 1.2 lacs
•Continuous three shift operation
•Looking forward for Loco wheel production
•Axle forging from bloom a parallel activity
•Final product: Wheel sets & loose wheels
•Total production connected by LAN

40. Refractory Management

41. Prologue
•IR uses different types of furnaces
–High temp EAF & Ladle for cast steel
–High temp Cupola for cast iron
–Medium Temp HT furnaces
–Low temp Tempering, Stress Relieving furnace
etc
•All these furnaces need different refractories
•In this section, EAF, Ladle, HT & Draw
furnace refractories are covered
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42. Introduction
•Refractory is the material which can retain
its strength at high temperature
•Both Graphite & Alumina are refractory,
but
–Thermal conductivity is widely different
–Those with low TC normally called refractory
•Used to conserve heat & protect shell
•Different type of refractories for different
furnace and different sections of a furnace
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43. 43
Chararecteristics of Refractory
•For furnace application, materials that
–Withstand high temperatures and sudden
changes
–Withstand action of molten slag, glass, hot
gases etc
–Withstand load at service conditions
–Withstand abrasive forces
–Conserve heat
–Have low coefficient of thermal expansion
–Will not contaminate the load
are called refractories
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44. EAF REFRACTORIES
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45. Electric Arc Furnace
•Most versatile equipment for production
Steel
•With high power rating furnaces, the load
on refractories has gone up considerably
•Some developments reduced consumption
–Water cooled panel
•85% of roof and 70% of side walls water cooled
–LF, EBT, DC furnace etc.
•In IR, only water cooled panels are used

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46. Structure of EAF
•A typical EAF has following basic areas
–Circular shallow bath with a dish shaped bottom
–Cylindrical side walls with slag door
–Dome shaped roof with circular openings for
electrodes, fume extraction etc.
–Tap hole
•Different service condition of various areas
–Requires different types of refractory materials
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47. Roof of EAF
•One of the most affected portion subjected to
all kind of stresses; thermal, chemical &
mechanical
–very high temperature often exceeding 1700°C
–Corrosive action of slag and metal oxides
•Specially iron oxide fumes which is deleterious
–mechanical stresses. Due to complicated design
•Spalling due to temp fluctuation
•Formation of low melting compounds

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48. Roof of EAF
•The problem has been tackled in two ways
–by improving the quality of refractories
–by changes in the design of laying
•Conventionally Silica Bricks
•Can not meet present day requirements
–High alumina materials (up to 95% Al
2O
3)
–castables with Cr oxide or pre-fabricated
shapes
–Water cooled roofs

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49. Side wall of EAF
•Subjected to
–Severe thermal shock
–corrosive slag action
–Mechanical abuse during charging etc.
•3 different zones, Slag, Roof drip & Hot spot
–Hot spots zones - most severe condition
•Exposed to very high arc temp as well as slag
•Reflected bath heat
•Mag-carb bricks with 10-15% carbon with
water cooled panel
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50. Hearth of EAF
•Hearth or bottom - a receptacle of liquid
metal and slag
•Has to withstand very arduous service
condition
–High temperature
–Thermal stress due to fluctuation in temp. before
and after tapping
–Slag and metal corrosion
–Mechanical abuse during charging
–High structural stresses during tapping at maxm.
tilt
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51. Hearth of EAF
•Divided into two sections
–Sub-hearth with few layers of high fired
magnesite bricks along with a fire bricks
lining against the shell
– Working hearth or bottom made by ramming
dolomite or magnesite, known as DRM
•Provides a monolithic, joint free surface
•Thickness around 250-300 mm
•Life 5000 - 10000 heats depends upon size of
furnace and operating parameters.
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52. Hearth of EAF
•DRM with little water & MgSO
4
•Ramming or vibration with a vibrator
•After around 50 heats, top layer scraped out
•Fresh layer of DRM rammed to replenish
•Heating up of cold furnace
–Light wood & charcoal lit up to drive out water
–Light scrap/boring about 500kg and arcing to heat
–Normal charging & arcing at low rate
–Holding at 1200
0
C for 30 min
–Slow heating to desired temp.
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53. Tap Hole & Launder
•High Alumina brick joined by Alumina mortar
•Top surface repaired by WRM occasionally
•Tap hole plug to block tap hole
–A mound with fireclay and graphite in water
–Tap hole packed
–Top surface with fireclay paste
–During tapping, the mass speared open
–Sometimes early opening of hole and metal
flowing
–Higher Graphite, easier to open
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54. LADLE REFRACTORIES
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55. Ladle & Refractory
•Ladle is a bucket shaped container, flat
bottom
–Refractory lined round steel container
–Carrying liq. Metal from furnace to pouring station
•In IR different refractories for ladle lining
–High alumina (70% min) brick
–High Alumina mortar
–High heat duty safety layer
–WRM
–DRM
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56. Ladle Preparation
•1
st
layer – High heat duty fireclay bricks to IS 8
•Then bottom layer of High Alumina brick
•Gaps packed with DRM, sealed with mortar
•Vertical wall built up with a gap, mortar joint
•Gap packed with DRM, burnt refractory etc.
•Built up to rim, keeping lip opening
•Finished with WRM paste
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57. Ladle Preheating Cycle
•Before use, a definite preheat cycle to follow
–Air dry for 24 hours
–Heat at a rate of 50
0
C per hr. till 350
0
C
–Soak for 4 hrs.
–Heat at a rate of 50
0
C per hr. till 1200
0
C
–Soak for 4 hrs.
–Lower at 900
0
C and hold till called for tapping
•A well prepared ladle lasts around 24 heats
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58. Synchronising Tapping Cycle
•Tap to tap time of a fce. ideally 2½ hrs.
•Two fce. should run simultaneously
–At a phase lag of 1¼ hrs
•Pouring time 1hr, manipulation 15 mins.
•When ladle is empty, next fce. ready for tap
•If not possible for any disruption
–Drain the ladle, clean by oxygen blowing
–put at ladle pre-heater and maintain 900
0
C
•Never allow the temp. to come below 750
0
C
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59. NORMALISING & DRAW
FURNACE
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60. NF and DF Refractory
•NF is Rotating hearth type fce.
•Different zones temp. from 500
0
C to 1000
0
C
•At low temp, 45% alumina brick
•At higher temp, 55% alumina brick
•Slow heat to 350
0
C, soak 3 hrs, raise to
9xx00
0
C
•Once lighted, should not be put off!
•At bottom and pedestal, 55% alumina mortar
•DF is walking hook type fce. at 500
0
C
•Lined with 45% alumina brick
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61. TESTING OF REFRACTORIES
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62. Common Test Parameters
•Chemical composition
–%age of Alumina, Magnesia, Silica, C, Cr-oxide
etc. as the case may be
–%age of Fe as FeO
–%age of Li, Na, K
•Bulk density
–Amount of refractory material within a volume
(kg/m3)
–High bulk density means high volume stability,
heat capacity and resistance
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63. Common Test Parameters
•Porosity
–Volume of open pores as % of total refractory
volume
–Low porosity = less penetration of molten material
•Cold crushing strength
–Resistance of refractory to crushing
•Permanent Linear Change(PLC)
–Permanent change in dimension after heating to
working temperature and cooling down
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64. Common Test Parameters
•Pyrometric Cone Equivalent (PCE)
•Temperature at which a ‘test pyramid’ (cone) fails
to support its own weight
–Tested against std. pyramid
of oxides that melt at specific
temperatures
•Refractoriness under load (RUL)
–Creep at high temperature
–Deformation of refractory material under stress at
given time and temperature

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65. Electric Arc Furnace Operation

66. Introduction
•Steel is primarily produced from pig iron
•Pig iron is produced from various iron ores
–Oxides, Carbonates, Sulphides etc. of iron
–Mixed with coke (reducing agent & Fuel)
–Charged in Blast furnace
–Reduced to iron in liq. form
–Contains large amount of other elements like
Si, Mn, S, P, etc.
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67. Introduction
•Treated in various converters like O/H,
Bessemer, L/D, etc to controlled chemistry
–End product is steel – normally mild steel
–Rolled to plate, sheet, bar, beams, channels
etc. for different commercial use
•Known as Primary Steel Making
•Normally Heavy Industry like TISCO, SAIL
•One more process is DRI
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68. Secondary Steel Making
•For specific composition (Low alloy, High
alloy & sophisticated) steels
•Mild Steel scrap as Raw material
•Melting in Electric arc furnace (EAF)
–Different treatment & alloy addition to achieve
desired chemistry
–Tapped in ladle
–Cast to shape or Intermediates
–Further rolled or forged to shape
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69. Secondary Steel Making & IR
•Mfg. of Cast Steel Bogies & wheels
•CASNUB bogies at CLW
•Demand of wheel > 3lacs/ anum
–Rail Wheel Factory (RWF) at Bangalore
•Capacity 1.2 lac/ anum – prodn. 2lac/anum!
•TOT from Griffin of USA
–Rail Wheel plant (RWP) at Bela, Patna
•Capacity 1.0 lac/ anum – new set up
•Copy of RWF
29/06/2015 69

70. Cast Steel Wheels
•Special Parabolic profile
•Very low P & S content
•Fine equiaxed grained structure
•High yield to tensile ratio resulting from
–Specially designed heat treatment process
•Round shaped non-metallic inclusions
•IR Specification R – 19 / 1993 Pt-III
–Both for Carriage & Wagon Wheels

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71. EAF OPERATION
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72. Furnace Charge
•Graded Steel Scrap with low S & P
–Mostly from Rly. source
•Light scrap – 15 %
•Medium scrap – 35 %
•Heavy scrap – 60 %
•Flux
–Fresh Lime with 90% CaO Min.
•Carburising agent
–Graphite or Petroleum Coke with low S
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73. Charging Quantity & Sequence
•For about 20MT yield
–22MT Scrap, 200Kg Coke & 1200Kg lime
•Pet coke and 80% of total lime to be
charged at the bottom
•Then light scrap
•Heavy scrap and foundry returns
•Light boring & turning

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74. Operation Sequence
•Lifting of Electrodes
•Opening of hood
•Charging of RM
•Closing the hood
•Lowering of Electrodes
•Start Arcing
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75. Operation Sequence
•Primary Melting through arcing
•Scrap cutting by blowing oxygen
•1
st
sample around 1540
0
C with 90% melt
•O
2 lancing→2
nd
sample→Deslag→1620
0
C
•Carbon blocking → RSM → Rabling
•3
rd
sample→ Adjustment→ check samples
•Preheated ladle→ Alloy addition
•Melt temp. to1700
0
C → Tapping to Ladle
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76. Operation Sequence
•Slag removal from top
•Taking to JMP
•Al. star addition
•Covering JMP & tube insertion
•Placing of Graphite Mould
•Pressure pouring
•Cope parting & wheel separation
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77. Metallurgical Aspects
•Initial arcing & scrap cutting
–90% of scrap in molten pool
–Gen Chemistry; C>0.80%
•O
2 lancing or ‘C Boiling’
–Bath mixing
–Removal of Hydrogen & Nitrogen
–C reduction
–Dephosphorisation
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78. Phosphorus Removal
•Conditions for dephosphorisation
–Low temperature
–Viscous slag
–Oxidizing condition
–High Basicity (more than 2.5)
•All conditions are met at this stage
•P forms P
2O
5 and goes out as gas
•C also forms oxides and move out
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79. Metallurgical Aspects
•2
nd
sample to ensure C & P level
•Raising bath temperature
•C continues to loose due to dissolved O
2
•Add Mn to stop loss; Carbon blocking
–Mn is stronger deoxidiser
•Al → Si → Mn → C
•Slag off and add fresh lime as RSM
–200kg lime, 50kg graphite and 20kg FeSi
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80. Sulphur Removal
•Large reduction not practical in EAF
–Low S scrap, weeding axle box, rubber etc.
•Conditions for desulpherisation
–Reducing atmosphere
–High basicity preferably > 2.00
–High fluidity of slag.
–Intimate contact between slag & metal
–High temperature of the bath(preferably >
1650
0
C)


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81. Sulphur Removal
•Addition of RSM at high temp.
–S removal conditions are met
•Sometimes little Fluospar addition
–Fluidity increases
–Restrictive, as corrosive to lining!
•FeSi , strong deoxidiser but restrictive
•Rabling to get fresh interface
•Formation of CaS & going to slag
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82. Final adjustments
•3
rd
sample should ensure
–S & P within range
–C around 0.5%
•If not, charge Graphite powder
•Raise temp. to 1700
0
C, take 2 samples
consecutively, bring preheated ladle
•Add calculated amt.(based on analysis) of
FeSi, FeMn & Graphite in the ladle,Tap
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83. 29/06/2015 83
Tapping or Pouring
•Final deoxidation should be in the ladle.
•Temp of pouring depends on the Carbon &
other alloying elements in the steel.
•The size and geometry of casting also
determines the temp of pouring.
•Pouring temp should be optimised in the
lower side.
•Speed of pouring should be optimised on
the higher side.

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Power Consumption
•Ideal consumption of power
–462 KWH/MT (Ref. MSTS)
•Normally it should not exceed more
than 20% of the ideal Power.
•Practical power consumption is 650-700
KWH/MT for making medium carbon steel

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Optmising Power Consumption
•Top be loaded with turning & boring
•Will facilitate easy bore-in stage of
electrodes
•Excess heavy scrap should not be
charged at the bottom.
•This may cause damage to the bottom as
well as will take more time to lift the
material in melt down stage.

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Good Melting Practice
•Power consumption at various stage (PF=0.75)
–Bore-in 300 unit
–Melt down 396 unit
–Refining 066 unit
Total 762 unit
•Charge composition
–HMS 50%
–MMS 30%
–LMS, Turning & Boring 20%

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Good Melting Practice
•Avoid over heating of furnace
•Maintain ladle at > 900
0
C
•Specific pre-heating cycle of ladle
•Correct basicity of slag
•Pre-heated of Scrap & Ferro Alloys
•At least 20 point carbon boil is essential
•Clean steel can be produced in clean
and healthy furnace