APPLICATION OF THERMOMECHANICAL TREATMENT ON MEDIUM-CARBON MICROALLOYED STEELS CONTINUOUSLY COOLED FROM FORGING TEMPERATURE

In the high-production-drop-forging of parts for automobile and truck engines the classical quench and tempering (QT) of low-alloyed steels is nowadays - in a lot of plants in Europe - substituted by direct con tinuous cooling (CC) of microalloyed steels without the necessity of a dditional heat treatment and expensive straightening as well as stress relieving cycles. Nevertheless, there are some limitations on strengt h and toughness achievable by this technique. On two commercial medium -carbon (0.3%C) steels microalloyed with vanadium or vanadium and tita nium, modified deformation parameters were applied. The mechanical pro perties, determined by the tensile test, can be improved by decreasing the deformation temperature. Nevertheless, the values of yield streng th (resp. 0.2%-proof stress) as well as reduction of area remain infer ior to those after QT of the same steels.