Application of continuous cooling transformation diagrams for welding of steels

AbstractIn the search for better and more consistent properties in steel welds, the study of microstructure versus mechanical properties has indicated a clear need for a more systematic and detailed presentation of the γ→α phase transformation reaction. The usual method of presenting such data is the continuous cooling transformation (CCT) diagram which relates the composition, cooling rate, and austenite grain size of the material to its γ→α. transformation temperature and resultant microstructure. Many hundreds of such diagrams have been produced throughout the world to describe the transformation behaviour of most grades of commercial steel when subjected to various heat treatment procedures. The majority of these diagrams are designed for typical industrial heat treatment processes, which usually involve re-austenitisation in the low temperature region of the austenite phase field (850–900°C), followed by continuous cooling by quenching, air cooling, or furnace annealing. Unfortunately, such diagrams ...