Case hardening involves either carburizing or nitriding the surface of iron-base alloys to increase wear resistance. This is commonly accomplished in heat-treating furnaces with the parts immersed in appropriate sources of those elements. However, for

small, noncritical jobs, it is possible to carburize parts with a welding torch.

The method requires a strongly carburizing flame, which is used to heat the surface to be hardened. It is best to use the white cone of the flame. The rate of carburization can be accelerated by turning the oxygen off occasionally, allowing a carbon soot to form on the surface. The depth of the case is determined by the time the part is heated and the maximum temperature achieved. Melting should be avoided. Hardening is assured by quenching the parts in water immediately after being treated.

 

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