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Wednesday, 13 November 2013

Case Hardening Process - Pack Carburizing

Pack Carburizing
Points : Pack Carburizing, Definition Definition The steel to be carburized is packed in “boxes,” completely surrounded by the compound, boxes that are usually made of a heat resistant alloy. After sufficient time at heat. the boxes are either slow cooled in the furnace or removed from the furnace opened. and the steel parts quenched:
The compound can be used repeatedly, with additions to replenish carbon used and mechanical losses. The case depth is a function of time and temperature. The maximum carbon content at the surface is a function of the efficiency of transfer of carbon from compound to surface of the steel and also of the temperature. This surface carbon content may be above 1 %, but there is no need for much more than that figures. The energizers, time, and temperature are chosen so as to regulate the carbon content in the outer layer to the desired value.

Case depth can be judged from fracture, usually of sample pins placed in the box with the pieces to be carburized. If greater precision of measurement is desired that can be obtained from judging the depth of carburization by the fracture, the cross section of the specimen may be polished and etched, and the depth may be measured by a microscope equipped with a scale in the eyepiece, or by some other optical method. The case depth can also be measured by machining off thin layers of the surface and analyzing each layer for carbon content.

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