Prediction of defects and analysis of grain flow in crank shaft forging by process modeling

Crankshaft is the most critically loaded part in the auto assembly. Crankshafts are increasingly made by steel forging to achieve required mechanical properties. New grades of steels such as air cooled forging steels and micro alloyed steels are used for crankshaft forging. Non-linear FEM analysis based process modeling can be applied to the forging of crankshafts. In the paper, authors discuss the application of FEM analysis based process modeling of crankshaft forging for analysis of grain flow and heat treatment. Three case studies are presented. In the first case, the grain flow evolution during the forging is presented in different cross sections. By an analysis of the velocity vectors, defects such as laps, folds, and underfills in forged crankshafts can be predicted. In the second case, the effect of centerline segregation causing a crack in the crankshaft is discussed. During forging the centerline segregation in the billet (workpiece) can get shifted due to deformation to regions close to the open surface of the crankshaft. In such instance, the crank shaft can fail during machining or heat treatment. In the third case, application of process modeling to heat treatment of crankshafts, to predict the residual stresses and distortion is presented. It is demonstrated that FEM analysis based process modeling of crankshaft forging can be a useful tool for the designer, forging process engineer, tool designer and quality / testing engineer.