AGMA 15FTM05 PDF

The basis for high fatigue performance in high hardness steel originates in precise inclusion engineering. In addition, recent research shows that by changing the alloying strategy, an increase in the bending fatigue limit can be achieved similar to an additional shot-peening process. Therefore, the near surface structure will exhibit excellent mechanical properties and compressive residual stresses in the ascarburized condition.

The current paper describes the potential of clean steel for new approaches in transmission gear box manufacturing and possibilities to meet the future demands of being smaller, lighter and managing higher torque. One important factor is the bending fatigue performance of the gear teeth where an increasing fatigue strength is required. The paper discusses how shot peening might be eliminated in highcleanliness, as-carburized steel components using an alternative composition. The fatigue performance of such a solution is compared to conventional grades used today, both with and without shot peening.

The full benefit of this new steel design can be obtained by using a high-quality steel with a decreased number of critically-sized inclusions in the loaded volume. Results from extensive testing support how this type of steel compares to commonly used carburizing steels. The effect of material cleanliness on contact fatigue is also examined through FZG pitting testing.

To address potential machining issues of clean steels, the paper also deals with the production process, including quantitative machining trials and the importance of tooling selection. The study is focused on the production of gears, dealing mainly with turning and hobbing. Initial results show how these clean steels can be machined in full scale production in standard conditions with equal or better efficiency and cost.