Patent ID: 7827692
Filing Date: 2010-11-09
Classification: B21K,F16H,Y10T

Abstract:
1. A method for obtaining a bevel gear made from powder metal having a variable case depth profile formed in a plurality of teeth comprising the sequential steps of: compacting a metal powder into a preform having a nearly uniform initial carbon content throughout said preform, said preform having at least one cross-sectional surface desired to have a variable case depth profile; sintering and carburizing, sequentially or simultaneously, said preform at a desired temperature, said carburizing substantially increasing an initial carbon content to provide a controlled carbon atmosphere, and maintaining said preform in said controlled atmosphere for a predetermined period of time to obtain an initial carbon case having a substantially constant carbon case depth; forging said preform in a forge at a forge temperature and a forge pressure to obtain a substantially dense and near net shape forged part with said variable case depth profile symmetrical about said plurality of teeth, wherein said variable case depth profile is achieved by utilizing a die set of the forge to variably enhance critical flow of metal, said die set being shaped to cause some portions of said initial carbon case in said plurality of teeth to be stretched and thinned and other portions of said initial carbon case in said plurality of teeth to be thickened and deepened during forging of said plurality of teeth; and cooling said forged part; wherein said plurality of teeth of said bevel gear extend radially in the same general direction as a rotational axis of said bevel gear, but are inclined with respect to said rotational axis, such that during forging the die set forges said plurality of teeth at an angle relative to said rotational axis.