Flame hardening, Induction Hardening, Laser Hardening n Electron beam hardening

1. Selective Hardening
Processes
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2. Why Selective Hardening
 1. Parts to be heat-treated are so large
 2. Only a small segment, section, or area of the
part needs to be heattreated
 3. Better dimensional accuracy of a heat-treated
part
 4. Overall cost savings
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3. Methods of selective hardening
 Flame Hardening
 Induction Hardening
 Laser Hardening
 Electron Beam Hardening
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4. Flame hardening
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5. Features of Flame Hardening
1. Oxy acetylene torch is used
2. Torch is adjusted so that temp. is above critical range but
below 850°C
3. Torch is moved so that part is heated uniformly followed
by quenching
4. Tempering is done to reveal stresses
5. For good results carbon content should be between 0.3-
0.6%
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6. Advantages
Very rapid n provide
deep cases upto
6mm
Zone Hardening is
possible
Disadvantages
Depth of heat
penetration into metal
is difficult to control
Only certain steel can
be hardened
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7. Induction Hardening
 Process involves induction heating with Induction coil.
 Heating Effect is produced on the surface by Induction.
 Temperature produced is about 750-800°C
 Hardness to a Depth of 0.8mm is achieved in 1 to 5 secs.
 Suitable for heat treatment for camshafts, crankshafts,
gears etc..
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8. Advantages
 It is faster. Effect is produced in 1
to 5 secs.
 Irregular shapes can be handled
easily
 Depth of case can be controlled by
varying freq. and time
 Accuracy is possible and entire
process is cleaner
Disadvantages
 Steel required is more expensive
 Hardness depends on C content.
Therefore higher hardness is
obtained only if expensive alloy
steel is used.
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9. Applications
 Hardening of Irregular shaped surfaces such cams chain links, piston rods…
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10. Laser Hardening
 Phosphate coating is applied over surface to absorb laser
energy.
 Temp. of 900-1400°C is obtained
 Depth of heat absorption can be controlled by varying
power of laser
 Materials self quenched heat transfer to cooler mass
inside
 As no quenching media is involved work pieces are clean
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11. Electron Beam Hardening
 In this heat source is a beam of high energy electrons
 Beam is manipulated using electromagnetic coils
 Process is self quenched
 Depth of case varies from 0.1 to 1.5mm
 It is a conventional option due to less energy consumption
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