DEVELOPMENT INSTALLATION AND TESTING OF CASE HARDENING SETUP

Mechanical Engineering

The heat treatment processes are generally carried out to the low carbon steels in the production field to change or modify the physical and mechanical properties of steals. The content of carbon in mild steel is less than 0.3% and in certain applications it requires sufficient hardness on surface of a component. Because of the lack of carbon, the metals are subjected to the carburizing Process. The carburizing process diffuses carbon in to the surface of heat treated components in an atmosphere controlled furnace. The purpose of carburizing is to increases the surface carbon content, on the surface region or case depth/layer. Fick’s law describes the instantaneous flow of diffusing atoms in the case layer. The case depth can be controlled by controlling the diffusion of carbon atoms through the surface layers of the work piece. Hard surface with tough core of work piece is obtained during subsequent quenching in a suitable quenching medium. Among the several types of carburizing process we selected pack carburizing process. We designed our own furnace set up for pack carburizing process. A case hardening mix with 13 parts of hardwood charcoal, 3 parts of barium carbonate, 2 parts of sodium carbonate and 1 part of whiting powder was prepared to get carburizing medium. Test specimens were placed at the centre of this carbon mixture in steel container. This mixture would work on the principle of “carburization” of the mild steel surface. The carbon content in the charcoal penetrates the steel surface, and changes it to a carbon-steel ot tool-steel. This was then hardened by heating and quenching in water or oil in the normal manner. Investigations were carried out to study the effects of heat treatment on the mechanical properties of low carbon steel by conducting Impact test, Tensile test and Rockwell Hardness Test and the properties before and after surface hardening process were analyzed. The result shows that the case hardened steel has excellent combination of tensile strength, impact strength and wear resisting surface which is very attractive for power transmission use.

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