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What is Induction Hardening In Heat Treatment of Metals ?

 Induction Heating has proved satisfactory for many surface hardening operations as required on the bearing areas of  the crankshafts , camshafts, axle shafts, and similar wearing surfaces. It differs from ordinary case - hardening practice in that the analysis of the surface steel is not changed, the hardening being accomplished by an extremely rapid heating and quenching of the wearing surface which has no effect on the interior core. The hardness obtained in induction hardening is the same as that obtained in conventional treatment and depends on the carbon content.


In this process, a high - frequency current of about 2000Hz is passed through a copper inductor block which acts as a primary coil of a transformer. The block is placed around but does not touch the surfaces to be hardened. The heating effect is due to the induced eddy current and hysteresis loss in the surface material. The hardening temperature is about 750*C to 760*C for 0.5 % carbon steel and 790*C to 800*C for alloy steel. The heated areas are then quenched immediately by sprays of water delivered through numerous small holes in the block. Both automatic and hand control can be employed. A depth of case of approximately 3mm is obtained in about 5 seconds. 

Although the equipment cost is high, it is practiced by the advantages of the process used, which include fast operation, freedom from scaling, clean operation, little tendency for distortion, no manual handling of the hot parts, and low treating cost. Medium carbon steel has proved satisfactory for parts, and the nature of the process has practically eliminated the necessarily for using costly alloy steels. 


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