METHOD FOR MANUFACTURING TRANSFER DRIVE AND DRIVEN GEARS FOR AUTOMATIC TRANSMISSION

摘要

PURPOSE: A method for manufacturing transfer drive and driven gears for automatic transmission is provided to reduce noise and greatly improve contact fatigue strength by applying carbonitriding process instead of existing carburizing heat treatment process. CONSTITUTION: The method comprises the steps of forging a workpiece; heat treating the workpiece at a temperature of 750 to 800 deg.C for 20 to 30 min while introducing NH3 gas having a concentration of 2 to 2.5% based on the atmospheric pressure into heat treatment furnace; maintaining the workpiece at a temperature of 900 to 950 deg.C for 300 min so that the workpiece is maintained to a viscosity level of 0.7 to 0.9 centipoise; and maintaining the workpiece at a temperature of 800 to 850 deg.C for 20 to 30 min while introducing NH3 gas having a concentration of 2 to 2.5% based on the atmospheric pressure into the heat treatment furnace.