Use of Navy C-rings to study and predict distortion in heat treated components: experimental measurements and computer modelling

Abstract

The Navy C-ring has been one of the most common types of specimen used for observing the dimensional changes (distortion) after heat treatment. The dimensional changes in the Navy C-rings are generally assumed to be comparable to those in an actual heat treated component. In this paper, we first review the various types of C-rings that have been used, and the results obtained for size and shape distortions for steels that have been carburised or nitrocarburised. An overview is then presented of the parameters that are included in simulation models to predict internal stresses and distortion. Finally, we present our own experimental and modelling results for the distortion in 1010 steel C-ring samples (three thicknesses) and an automotive component (torque converter piston) subjected to a gas ferritic nitrocarburising treatment. The predictions, on the basis of the nitrocarburised layer, and measured distortions were in better agreement for the thinner C-rings where the thickness was comparable to the thickness of the actual component. Hence, the distortion of C-rings with smaller bulk volume to nitrocarburised volume (V/V_N) ratio compares favourably with the simulated values.

Keywords:

• Navy C-rings
• Size distortion
• Shape distortion
• C-ring modelling
• SAE 8620
• PS-18
• SAE 1010

Acknowledgements

This research is funded by the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant awarded to Professor D. O. Northwood.