Predicting the occurrence of grind hardening in cubic boron nitride grinding of crankshaft steel

Pearce, T. R.A.; Harrison, A. J.L.; Fricker, D. C.

Abstract

Grind hardening is a stock removal grinding operation in which the heat generated in the grinding zone is used to heat-treat the workpiece surface to a specified depth. A thermal model to describe this process has been developed from the original Jaeger modelling and has been used to predict subsurface time-temperature profiles in the dry cylindrical grinding of 42CrMo4 crankshaft steel using cubic boron nitride (CBN) wheels. By comparing with experimental hardness depths, partition ratios were calculated and a polynomial fit applied to the proportion of specific energy entering the workpiece as heat, as a function of specific removal rate. By using this polynomial to provide the heat input to the thermal model, a theoretical chart of workpiece surface speed against depth of cut has been produced, which shows the regions in which grind hardening can be achieved to specified depths. The chart shows lower limits where the martensitic transformation temperature has been reached at certain specified depths and an upper limit where melting starts at the contact surface between the CBN grinding wheel and the workpiece. This chart has then been compared with experimental results for the specific case of a hardened depth of 0.5 mm or greater, with good agreement. The predictions indicate that there is an upper limit on workpiece speed if grind hardening is to be achieved, and that the limiting speed reduces as the required hardness depth increases. The predictions also indicate that there is an optimum work speed of around 10 mm/s for hardness depths below 1.5mm and an upper limit below 4 mm/s for hardness depths around 2 mm.

Citation

Harrison, A. J., Pearce, T. R., & Fricker, D. C. (2004). Predicting the occurrence of grind hardening in cubic boron nitride grinding of crankshaft steel. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 218(10), 1339-1356. https://doi.org/10.1243/0954405042323577

• Journal Article Type: Conference Paper
• Publication Date: Oct 1, 2004
• Journal: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
• Print ISSN: 0954-4054
• Publisher: SAGE Publications
• Peer Reviewed: Peer Reviewed
• Volume: 218
• Issue: 10
• Pages: 1339-1356
• DOI: https://doi.org/10.1243/0954405042323577
• Keywords: grind hardening, cubic boron nitride (CBN) grinding, Jaeger thermal model
• Public URL: https://uwe-repository.worktribe.com/output/1062486
• Publisher URL: http://dx.doi.org/10.1243/0954405042323577
• Additional Information: Additional Information : This work formed part of an EC funded collaborative project. A follow-on project was set up with a different set of partners. Knowledge transfer has also occurred through presentations to industry at the IGT Annual Seminars. Grind hardening offers the potential of eliminating separate hardening processes, which require large and expensive equipment. The thermal modelling described in this publication explained apparent experimental discrepancies in measured hardness depths under different grinding conditions.