Selection of direct cooling conditions for automotive lever made of microalloyed steel

The paper presents issues concerning determination of forging and controlled cooling conditions in aspect of application of direct cooling of as-forged microalloyed steel. The study concerns realization of thermomechanical treatment directly after forging, oriented at producing desired microstructure and required final mechanical properties. In order to determine forging conditions and most favourable cycle of cooling, numerical modelling with finite element method was used. To select appropriate forging temperature, actual temperature in critical locations of the part was traced during the entire forging cycle. On assumption of predefined parameters of forging process and subsequent forced-air continuous cooling, effectiveness of forced-air acceleration was investigated from the standpoint of producing necessary cooling rate. The direct cooling regimes were verified with tensile testing and hardness measurement, illustrating qualitative analysis of obtained microstructure. Determined forging/cooling conditions served as guidelines for industrial realization of controlled processing of drop forged automotive lever oriented at fine-grained ferrite–pearlite or acicular ferrite microstructure and required level of mechanical properties.