Analysis of microstructure evolution in the forging process of a windmill main shaft

The paper presents the results of an investigation of microstructure evolution in hot-deformed steel in the process of forging of large forgings. The objective is to create a feedback between the microstructure and the material flow stress in the finite element modelling. Using a forging of a windmill main shaft as an example, the description of the technological process is presented, focused on phenomena occurring in the microstructure during hot-forging. An investigation of the microstructure during and after forging of a shaft was performed and the results are presented in the paper. The analysis include the metallographic work after the last stage of forging and simulations of microstructure evolution during subsequent stages of the production cycle, based on temperature changes derived from industrial practice. Predictions of microstructure evolution allowed plotting changes of grain size and recrystallized volume fractions versus time during forging and reheating operations.