Heat treatment practice

1. HEAT TREATMENT
&
ITS APPLICATION IN AUTOMOTIVE
INDUSTRY
G.VEERAPPAN M.E, M.B.A
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2. GRATITUDE TO MY MENTOR
Dr.M.RAVICHANDRAN
ASSOCIATE PROFESSOR
K.RAMAKRISHNAN COLLEGE OF
ENGINEERING, TIRUCHIRAPALLI.
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3. Topics to be Covered
• Heat treatment and its purpose
• Types of Heat treatment
• Case Hardening and it types
• Masking of components
• Piston
• Gears
• Crankshaft
• Connecting Rod
• Leaf Spring
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4. Heat Treatment and its purpose
• An operation or combination of operations
involving heating and cooling of a metal/ alloy
in solid state to obtain desirable condition.
• Purpose
• Relief internal stresses
• Harden and strngthen metals
• Improve machinability
• Improve ductility and toughness
• Increase wear and corrosion resistance of materials
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5. STAGES OF HEAT TREATMENT
• Heating a metal rod to specified temperature.
• Holding at that definite temperature for a
sufficient period to allow necessary changes
to occur.
• Cooling at a rate necessary to obtain desired
properties.
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6. Heat treatment Process
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7. TYPES OF HEAT TREATMENT PROCESS
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8. TYPES OF HEAT TREATMENT
• Annealing.
• Normalizing.
• Hardening.
• Tempering.
• Case hardening.
• Surface hardening.
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9. ANNEALING
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10. ANNEALING
• Heating the steel rod to proper annealing
temperature (i.e 823 degree celsius).
• Holding the steel rod for definite period based
on the thickness or diameter
• Cooling veryslowly in the furnace
• Components: washers, connecting rod ,
Spanners
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11. Annealing in sheet metal bending
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12. CONNECTING ROD
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13. Connecting Rod Stress Diagram
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14. MACHINING METHOD
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15. Annealing of Connecting Rod
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16. Annealingof spanner
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17. NORMALIZING OR AIR QUENCHING
• It is the process of heating steel to about 40 -
50⁰ C above its critical temperature.
• Hold for short time.
• Cooling in still air.
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18. NORMALIZING OR AIR QUENCHING
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19. DIFFERENCE BETWEEN ANNEALING
AND NORMALISING
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20. ANNEALED & HARDENED METAL
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21. HEAT TREATMENT IN ROLLING
OPEARTION
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22. HARDENING BY QUENCHING
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23. Hardening by quenching
• Alloys are heated above the critical
transformation temperature for the material,
then cooled rapidly enough to cause the soft
initial material to transform to a much harder,
stronger structure.
• Microstructure obtained is martensite.
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24. Hardening by quenching
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25. LEAF SPRING
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26. LEAF SPRING HARDENING
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27. GEAR HARDENING BY QUENCHING
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28. TEMPERING
• The process involves reheating the hardened
steel to a temperature below the lower critical
temperature, holding it at that temperature
for sufficient time and then cooling it slowly
down to the room temperature.
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29. TEMPERING PURPOSE
• A hardened steel piece, due to martensitic
structure, is extremely hard and brittle, due to
which it is found unsuitable for most practical
purposes. So a subsequent treatment is
required to obtain a desired degree of
toughness at the cost of some strength and
hardness to make it suitable for use. It is
especially true in case of the tools. This is
exactly what is mainly aimed at through
tempering of steel.
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30. TEMPERING
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31. TEMPERING COLORS OF STEEL
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32. TEMPERING RANGE
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33. 4/28/2021 33

34. Hardness Vs Tempering
temperature
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35. 4/28/2021 35

36. Al wheel hub manufacture process
& Heat treatment
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37. Al wheel hub manufacture process
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38. Case hardening
• Case hardening produces a hard and wear-
resistant outer layer while preserving the
ductile-strength of the interior. Case
hardening a gearbox components creates a
hard outer-shell and a pliable inner layer. The
hardened layer is called the case. The
thickness of the hardened layer is referred to
as the case depth.
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39. Some Types of Case Hardening to
be covered
• Carburizing – Add carbon to the surface of
steel.
• Nitriding- Add nitrogen to the surface of steel.
• Carbonitriding – Add carbon and nitrogen to
the surface of the steel.
• Induction Hardening
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40. 4/28/2021 40

41. Carburizing case hardening
• Carburizing processes, which mean that
carbon is introduced into the steel to increase
its strength. Carburizing treatments are useful
for steels that have a carbon content between
0.15 to 0.25 percent. After the treatment, the
carbon content at the surface of the steel
should be raised to 0.8 to 1.0 percent.
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42. Atmosphere carburizing process
• In the atmosphere carburizing process, steel parts
are heated in a furnace and mixed with carbon-
containing gases such as methane, carbon monoxide,
and carbon dioxide. The steel absorbs the carbon
from these gases and diffuses from the surface of the
steel inwards. Once they are mixed, the parts are
then cooled, typically using oil, but brine, molten
salt, water, or a polymer solution can also be used.
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43. Vacuum carburizing
• Vacuum carburizing involves heating the steel in a
vacuum chamber. Once the parts reach the
necessary temperature, the carbon gases are
injected into the chamber. This method offers several
advantages over atmosphere carburizing, including
better control of carbon diffusion, which minimizes
dimensional distortions. The steel parts are then
quenched in an inert gas, such as nitrogen, or in one
of the liquids described above. Finally, the parts are
tempered in a similar manner to atmosphere
carburizing.
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44. 4/28/2021 44

45. PACK CARBURIZING
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46. PACK AND GAS CARBURIZING
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47. SOLID OR PACK CARBURIZING
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48. SOLID OR PACK CARBURIZING
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49. SOLID CARBURIZED GEAR RIM
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50. CARBURIZING FOR GEAR
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51. GAS CARBURIZING
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52. NITRIDING
• Addition of Nitrogen in the outer case of the
base metal is Nitriding.
• The nitriding of metals is a process that allows
you to change the properties of surface
hardness, wear, corrosion and thermal
resistance of the material, They are used, in
order of importance in the treatment of
ferrous metals, refractory metals and, more
recently, of aluminium
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53. NITRIDING
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54. CUMMINS DIESEL ENGINE PISTON
CHEMICAL ANALYSIS
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55. PISTON EDS ANALYSIS
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56. Nitriding
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57. Single Nitriding furnace
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58. NITRIDING BATCH FURNACE
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59. NITRIDING FURNACE
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60. NitridING Application
• The process is used in the treatment of plastic
injection moldings, automotive parts (valves,
gears, pistons, etc.), aluminium extrusion dies,
cutting tools and machining metal, cutting
punches matrices in general treatment
prostheses, etc.
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61. Features of Nitriding
• High surface hardness (typically > 67 HRC)
• Resistance to wear
• A minimum of distortion and deformation
(less than, for example,
carburizing/hardening)
• Improved fatigue life and other fatigue-
related properties
• Resistance to corrosion (except for 300- series
stainless steels)
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62. • Nitrogen in atomic form is produced by the
decomposition of ammonia when it comes
into contact with the hot surface material
according to the reaction described below:
2NH3 → 2N + 6 H
2N + 6 H → N 2 + 3 H2
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63. Principle of Nitriding
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64. Nitriding Temperature Vs Time
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65. Nitrided Piston Ring
Nitrided Outer
Layer
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66. Ability of Achievement of Hardness
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67. Wear resistance of Nitrided and
carburized layer
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68. 4/28/2021 68

69. MASKING TECHNIQUE FOR HEAT
TREATMENT
• COPPER PLATING
• STOP OFF PAINTS
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70. GEAR MASKING
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71. GEAR MASKING
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72. GEAR MASKING
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73. Fiat Avio studied the effects of copper
plating on gears
• Copper plating experienced a chemical interaction between the
tooth flanks and the copper plating. This interaction is known as
hydrogen embrittlement where the hydrogen enters the material
during the electro-plating process. The result is a diminishment of
strength and fatigue life of the gear (but not hardness).
• Additional tests show the embrittlement effect can be reduced by
heating the pinions to 150 deg C and tempering. The resulting
residual loss in strength was reduced to 7%.
• A common cure for hydrogen embrittlement is tempering at the
proper temperature, but it must be done immediately after plating.
Thus, with tempering you can reduce the loss of bending strength
to 7%. However, 7% is well within the usual scatter in bending
fatigue tests.
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74. INDUCTION HEAT TREATMENT SHAFT
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75. Piston rod induction heat treatment
machine
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76. Induction hardening
• Induction hardening is a method of quickly
and selectively hardening the surface of a
metal part. A copper coil carrying a significant
level of alternating current is placed near (not
touching) the part. Heat is generated at, and
near the surface by eddy current and
hysteresis losses. Quench, usually water-based
with an addition such as a polymer, is directed
at the part or it is submerged. This transforms
the structure to martensite, which is much
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78. Benefits of Induction Hardening
• Increased Wear Resistance
• Increased Strength & Fatigue Life due to the Soft Core & Residual Compressive
Stress at the Surface
• Parts may be Tempered after Induction Hardening to Adjust Hardness Level, as
desired
• Deep Case with Tough Core
• Typical case depth is .030” - .120” which is deeper on average than processes such as
carburizing, carbonitriding, and various forms of nitriding performed at sub-critical temperatures.
• Selective Hardening Process with No Masking Required
• Relatively Minimal Distortion
• Allows use of Low Cost Steels such as 1045
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79. CRANKSHAFT
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80. INDUCTION HARDENING OF
CRANKSHAFT
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81. CRANKSHAFT HARDENING
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82. • Induction hardening is a method of quickly
and selectively hardening the surface of a
metal part. A copper coil carrying a significant
level of alternating current is placed near (not
touching) the part. Heat is generated at, and
near the surface by eddy current and
hysteresis losses. Quench, usually water-based
with an addition such as a polymer, is directed
at the part or it is submerged. This transforms
the structure to martensite, which is much
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83. THANK YOU
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84. ANY QUERIES
• Email id: veerappangopathy@gmail.com
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