Effect of forging sequence on evolution of parameters controlling microstructure in multistage drop forging process

The study presents the comparative analysis of competitive techniques of forging and analysis of the effect of the forging sequences on microstructure development. Starting with industrial practice of hammer-forged elongate geometry, two competitive processes were numerically analysed in term of forging economy and quality. Numerical modeling of temperature, strain and strain rate fields let theoretical prediction of the microstructure development in multi-stage drop forging process consisting of progressive sequence of multiple blows in preforming and die-impression forging operations. The aim of the modeling was prediction of the parameters of austenite in as-forged condition, which in thermomechanical controlled processing form the restored austenite condition prior to direct cooling. Dynamic recrystallization kinetics was analyzed with use of Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, taking advantage of numerically calculated of temperature, strain and strain-rate in selected location in the volume of the part. The obtained results show the possibility of look-ahead microstructure prediction and form the basis for comprehensive selection of the forging process parameters aimed at producing required microstructure and its uniformity in the bulk in multi-stage hammer-forging process.