Flywheel starter ring gear failures and hardness variation reduction in surface hardening process

In general technical applications, truck heavy duty engine flywheel starter ring gears teeth is conventionally induction hardened and tempered in order to meet metallurgical aspects on specification. Especially for large sectioned starter ring gears (in this case diameter of the gear is 470 mm) the critical issue is to maintain a stable hardness distribution on gear cross sections. These hardness variations in process could yield to: 1. High scrap costs due to out of specification parts. 2. Increase in tact time in process, decrease in labor efficiency due to scrap rate and excessive hardness measurements. 3. Potential risk of failure on engine in low mileages. 4. 100% hardness measurements in ongoing process which leads to time and cost waste. This technical paper summarizes the case study conducted for truck flywheel starter ring gears with diameter of 470 mm in order to reduce hardness variation by optimization of induction hardening and tempering processes