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INDUCTION TO HARDENING

BY JEEVAN B M1ST SEM, AUTOMOTIVE ELECTRONICSP151905SJCE,MYSORE

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Contents

• Introduction• history• Tempering• Methods of hardening• Applications of hardening• References

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INTRODUCTION

• Hardening is process in which steel is heated to a temperature above the critical point, held at this temperature and quenched in water, oil or molten salt bath

• Types of hardening are quench hardening, work hardening, precipitation hardening, surface hardening

• Types of surface hardening are flame hardening, induction hardening, carburizing, cyaniding, nitriding, carbonitriding.

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Con..

• Induction hardening is a form of heat treatment in which a metal part is heated by induction heating and then quenched

• Material is heated by passing the current that generates alternating magnetic field resistance leads to heating of the metal

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History

• The basis of all induction heating systems was discovered in 1831 by Michael Faraday.

• Faraday proved that by winding two coils possible to create a momentary electromotive force in the second winding by switching the electric current in the first winding on and off.

• Using this principle invented electrical generators and electric motors, which are variants of the same thing)

6 • But the disadvantages of these system is they generate a heat

• To avoid this heat generate used laminated cores and other methods to minimize the effects

• Engineers at Midvale Steel and The Ohio Crankshaft Company drew on this knowledge to develop the first surface hardening induction heating systems using motor generators.

• Modern day induction heating units utilize the latest in semiconductor technology and digital control systems to develop a range of powers from 1 kW to many megawatts

7 Basic principle

• All metals conduct electricity, while offering resistance to the flow of this electricity

• The resistance to this flow of current causes losses in power that show up in the form of heat

• This is because, according to the law of conservation of energy• The losses produced by resistance are based upon the basic

electrical formula:

P=I^2R

8Practical way of heating

AC current through a copper coil, and the part to be heated (the work piece) is placed inside the inductor

As soon as AC is supplied work piece enters the magnetic field, circulating eddy currents are induced within the part

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these eddy currents flow against the electrical resistivity of the metal, generating precise and localized heat

This heating occurs with both magnetic and non-magnetic parts, and is often referred to as the "Joule effect“

Secondarily, additional heat is produced within magnetic parts through hysteresis – internal friction that is created when magnetic parts pass through the inductor

continue

10 Factors to consider

• Characteristics of work pieceo METAL OR PLASTIC

o MAGNETIC OR NON-MAGNETICo RESISTIVITY

• Inductor(coil) design• Power supply• Degree of temperature range is required

11Methods of induction hardening

Single shot hardening

• Single-shot hardening means the complete hardening zone is first heated and then quenched

• hardening can be achieved with a multi-turn coil that encircles the entire hardening zone

• Single shot is often used in cases where no other method will achieve the desired result

• Drawback--The coil design can be an extremely complex and involved process

12 Traverse hardening• In traverse hardening systems the work piece is passed through the

induction coil progressively and a following quench spray or ring is utilised

• The component is fed through a ring type inductor which normally features a single turn

• Traverse hardening is used extensively in the production of shaft type components such as axle shafts, excavator bucket pins, steering components, power tool shafts and drive shafts

13 Advantages  Specific limited local hardening is possible The distortion can be kept very small The hardening times will be shorten Heating Process Controllable and Repeatable Improved Product Quality more production rate

14Application

Industrial application

Medical application

Work piece with more length like axels shafts can be operated

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Disadvantages

High capital investment is need Each shape of a components requires inductor to be designed for it,

this comes in difficult in induction hardening

16 References

Induction hardening a quick guide to methods and coil Effect of induction hardening on high carbon steel forgings-subir danda Induction heating-Qadri Mayaleh & AbdelRahman Abbass http://www.gh-ia.com/induction_heating.html http://www.uihm.com/en/Induction-Technology/What-is-Induction-He

ating-and-induction-Principle-15.html#.VlFazPmqpBc http://www.efd-induction.com/~/media/Articles/InductionHardening_

MethodsCoils.ashx http://ezinearticles.com/?Induction-Hardening&id=4803616 http://www.uihm.com/english/What-is-Induction-Hardening-12-77-340

.html#.VlGkgvmqpBc

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THANK YOU ALL