Thermomechanical processing and inclusion engineering of microalloyed forging steels

This paper reports the results of a study of commercial heats of a medium - carbon microalloyed forging steel, which combined the new concepts of inclusion engineering and thermomechanical forging. Two EAF heats of SAE grade 1541 steel were prepared following 2 different ladle steelmaking practices and 2 different microalloying approaches. A thermodynamic model was employed to determine the slag composition which would produce glassy exogenous and indigenous oxide inclusions following slag-metal equilibration. Ca treatment produced a high volume fraction of glassy exogenous calcium-aluminum-silicate inclusions, which reduced tool wear under high speed machining conditions. Thermomechanical processing during hot forging produced refined ferrite + pearlite microstructures and carbonitride precipitation. These microstructural modifications increased the strength and ductility of TMP forgings compared with conventional forgings.