Strukturbildungsprozesse und Struktur-, Eigenschafts-Relationen in mikrolegierten Schmiedestählen nach thermomechanischer Behandlung mit variierenden Abkühlkonzepten

摘要

In the last years, the classical quenched and tempered (QT) steels have been progressively substituted for economically superior vanadium microalloyed steels with medium carbon content which are continuous cooled from the forging temperature. However, these steels perform comparably weak in terms of 0,2%-proof stress and ductility. A new post forging treatment has been developed therefore and proves a promising alternative to the continuous cooling of microalloyed steels with medium carbon content. The treatment consists of a two-step cooling process (slow-fast-cooling) and a subsequent annealing procedure at lower temperatures. The resulting mechanical properties compare to those of chromium-alloyed quenched and tempered steels. The present paper is focused on the development of the complex microstructure during the thermomechanical treatment with the continuous cooling and the new two-step cooling followed by annealing. It describes how the results depend on the variation of process parameters and microalloying as well as the relations between the final microstructure and resulting mechanical properties.