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Heat Treating - continued Induction hardening is a good general purpose heat treating method which requires the use of medium carbon steel (.030 - .050 C). Parts are heated by placing the target hardening area (usually the teeth in this context) in close proximity to a copper coil which surrounds the entire part, or a pointed tip the shape of one tooth space in the case of larger parts. An electrical current is run through the coil or tip and the magnetic resistance between the work piece and the coil or tip causes the work to heat up at a very rapid pace. When the work reaches its hardening temperature it is then quenched. Part distortion rates are similar to or slightly better than that of flame hardening. The carburizing method of heat treating results in the highest hardnesses of the three methods mentioned here, typically R/C 57 - 63, but the depth to which parts can be hardened is less than with either flame or induction hardening (.030 - .060 inches as opposed to .100 - .200). This method utilizes low carbon steel (.010 - .030 C). The part is heated in a carbon rich atmosphere, usually a furnace filled with a gas high in carbon content. As the part heats up it absorbs carbon into the exposed surface areas. After enough time has passed for the part to have absorbed an appropriate amount of carbon, and to have reached its hardening temperature, it is quenched. Unlike flame or induction hardening, parts are hardened all over rather than strictly on certain target areas such as the teeth of a sprocket or gear. Because the entire part is heated to a high temperature the distortion rates seen with carburizing are higher than with other methods. This can cause problems for gearing which requires highly accurate tooth forms, thus resulting in the need for post-heat treat finishing such as grinding of teeth or other critical surfaces such as bores or bearing journals. We would like to help you in any way we can in supplying your heat treated sprocket and gear needs, or determining the quality of products you are currently purchasing. If Linn Gear Co. can be of service to you please don't hesitate to contact us. Copyright by Gil Hartl, 1990 - 1998 back |