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Abstract
Billets of 42CrMoS4 steel were subjected to a programme including forging and rolling to different reduction ratios, followed by quenching and tempering to simulate online thermomechanical treatment (TMT) during rolling. The mechanical properties obtained were compared with those obtained by conventional heat treatment (CHT) (quenching from 860°C and tempering). It was found that increasing the hot reduction ratio from 18 to 60%, accompanied by a decrease in the finish rolling temperature from 900 to 750°C, enhances strength only at the expense of elongation, while rapid quenching instead of air cooling from the same finish rolling temperature yields improvements in both strength and ductility. It was also found that CHT provides higher hardness, whereas TMT provides higher impact toughness. TMT will confer major economic savings since the heat treatment is achieved online.