Development of Cr-alloyed high carbon sheet steel – BW AC C77MD – for the manufacture of clutch bearing rings by deep drawing

Clutch bearing rings are high-performance parts that require excellent cleanliness and microstructure homogeneity to meet their wear and fatigue requirements. To improve productivity and reduce costs, a modified Cr alloyed steel with high carbon content has been developed by bearing manufacturers in cooperation with steel producers, which is well suited in terms of formability and is widely used in the production of automotive components, where it is purchased in the form of the cold-rolled strip for forming. This work investigated the process parameters and critical characteristics for developing Cr-alloyed sheet steel with high carbon content to produce clutch bearing rings on an industrial scale. Tensile test, hardness test, optical microscopy (OM), and scanning electron microscopy (SEM) were used to evaluate the mechanical and metallurgical properties of the studied steel throughout the process (casting, hot rolling, cold rolling + batch annealing, and heat treatment). The results have shown that it is possible to tune the mechanical properties of high carbon steel at each stage of the process by using the proper heat and metallurgical treatment targeted at the requirements of the final application.(author)