Surface layer of work-piece only can be heated by electro-magnetic induction. High surface hardness, wear resistance and high fatigue limit can be obtained Compressive residual stress generated by induction hardening brings superior fatigue limit. Process following heat-treatment can be omitted because of little decarburization or scaling of work piece. Quick and economical for small lot production is available.
	Quenching spline part of shaft
Facilities INDUCTION HARDENING
MADE BY TOCCO(USA) 10KHz 150KW &O slash;300x2,000 Max CASE DEPTH 1~5 mm.	MADE BY DENSHIKAGAKU (JAPAN 200KHz 40KW Ø 50x600 Max CASE DEPTH 0.4 ~ 2.5 mm.
HARDNESS & RESIDUAL STRESS
Quenching hardness depends on carbon content of material not on hardenability of it. Hardness obtained by induction hardening is higher than it by ordinary quenching, because of compressive residual stress generated by the process. While maintaining hardness and residual stress, tempering is to be carried out in order to prevent deforming, grinding crack and to improve toughness.
	Carbon content & quenching hardness
Distribution of hardness & residual stress	Carbon content & tempered hardness
INDUCTION HARDENED DEPTH
For controlling induction hardening, as it is difficult to measure Austenitizing temperature directly, frequency(penetrate depth), power density, ampere and voltage, heating duration are used instead. The lower frequency is applied, the deeper harden depth is obtained. There are two kinds of heating up, those are one shot heating and progressive heating.
	Relationship between hardened depth and heating duration, power density and frequency
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