New understanding of steel chemistry will mean fewer rejects

Steel components that are distorted after hardening are a costly problem. The findings of a recent research project provide new understanding of the steel chemistry that gives rise to this problem. 

Anders Olofsson, Scania

Emil Stålnacke at Swerim has managed the Vinnova-funded project DistOVER, the aim of which has been to understand the factors behind, and minimise, the occurrence of distortions in rolled rings by studying the effects of chemical differences in steel blanks. 

"Scania, one our partners in the project, has to reject substantial numbers of the rolled rings that are used in the manufacture of heavy vehicles. Each step of production prior to the final operation, hardening, creates potential for distortion. We have followed the entire process from start to finish, thanks to the fact that Ovako, who delivers the steel, has also participated in the project." 

The DistOver project has verified a model that explains why certain rings become distorted and are warped or oval while others are not. Distortion is a result of differences in the chemistry of the steel blank; differences between the steel's core and the periphery. 

"Ovality is more pronounced if the chemistry deviates. We have been able to demonstrate that there are variations in the steel chemistry and that this clearly has an impact," says Emil Stålnacke, explaining that the next step, prediction and modelling of the chemistry, will help to reduce the incidence of distortion and thus, the number of rejects. 

Anders Olofsson, process engineer at Scania, explains. "For us, the project has been a great success. It has shown in real terms how variations in the steelmaking process have an impact on distortions after case hardening of transmission components. This would not have been possible without cross-sectoral collaboration and a project group with expertise spanning the entire chain of manufacturing. We will use this knowledge in setting future requirement specifications for steel blanks for precision components, since we see the necessity of reducing variations in input material." 

Photo: 3D-scanned ring wheel
Photo 2: Anders Olofsson, Scania