Induction Hardening and Flame Hardening

INDUCTION HARDENING

&FLAME HARDENING

BY:- SACHIN DEV ( GME/SL/14/4608 ) ANKIT KUMAR ( GME/SL/14/4609 ) ABHISHEK KUMAR ( GME/SL/14/4617 ) SHIVAM SONI ( GME/SL/14/4621 ) ABHISHEK SINGH ( GME/SL/14/4601 ) ASHISH PRAJAPATI (GME/SL/14/4606)

SURFACE HARDENING It is process of heat treatment  in order to increase the

hardness of the outer surface while the core remains relatively soft.

It increases wear resistance , resistance to high contact stresses , improve fatigue resistance and corrosion resistance.

CAM, RING GEAR, BEARINGS, etc. requires Surface Hardening.

SOME COMMON SURFACE HARDENING TECHNIQUES

• INDUCTION HARDENING

• FLAME HARDENING

• LASER BEAM HARDENING

• ELECTRON BEAM HARDENING

PRINCIPLEWhen the metallic workpiece (usually steel) is placed in a coil and current is flownIn the coil then current is induced on the surface of the metallic workpieceand it is heated upto above its critical temperature.

WHY CHOOSE INDUCTION HARDENING ?

• Has much faster heating rate than other methods.

• Provides for more control over outcome - Less distortion of workpiece - Easy control of hardness depth

• Heating can be localized for surface hardening - Allows the core metal to be unaffected

TYPICAL HEAT TREATMENT PROCEDURES

• An induction heater consists of an electromagnet - Creates a high frequency Alternating Current (AC).

• Heats the component(0.3%-0.7% of carbon content) to the

Austenitizing temperature.

• Holds it at temperature long enough to complete the formation of Austenite.

QUENCHING STAGE OF HEAT CYCLE

• Rapidly cools the metal until Martensitic transformation occurs.

• Changes structure from FCC to BCC.

• Causes a transformation of the initial structure of the steel into Martensite.

VARIATION OF DEPTH VS FREQUENCY

Where, d=depth of hardening p=resistivity f = frequency

For Deep Hardening a prolonged low frequencyHeating should be employed and vice-versa.

ADVANTAGES• Fast process• No Scaling or Decarburisation• Minimum chances of distortion• Selectively Hardening• Ease control of hardness depth• High wear and fatigue resistance

DISADVANTAGES• Equipment is more costly

FLAME HARDENING• It is a rapid high intensity heating,

economical method for selectively hardening specific areas on the surface of a part followed by an appropriate quenching method.

• Uses direct impingement of an oxy-acetylene gas flame onto a defined surface area.

• Used to treat components such as gears, shafts, cams, crankshafts, camshafts, etc.

TYPES OF FLAME HARDENING

• STATIONARY FLAME HARDENING:- requires specified area to be heated

• PROGRESSIVE FLAME HARDENING:- integrated quench capability

• SPIN FLAME HARDENING:- requires specified area to spin in front of flame head

• COMBINATION FLAME HARDENING:- couples the progressive and spinning methods

HEAT TREATMENT PROCEDURES

• It may be a single torch with a specially designed head that automatically indexes and heats the work material.

• Large parts such as gears or machine toolways with sizes or shapes that would make furnace heat treatment impractical, are easily flame hardened.

QUENCHING STAGE • After heating

is completed, the parts are quenched by water spray or by complete immersion in water.

DEPTH OF HARDENED LAYER DEPENDS ON FOLLOWING PARAMETERS

• Distance between gas flames and the component surface.

• Gas pressure and ratio.

• Rate of travel of flame head or component.

• Type, volume and application of quench.

ADVANTAGES• Fast process

• Less distortion surface

• Selectively hardening

• Faster localized cooling rates

DISADVANTAGES• Some oxidation or decarburization may occur as compared to induction

hardening.• Explosive fuel gases have to be used cautiously.

QUESTIONS ?