Influence of the chemical composition on the Thixoformability of steels

This work deals with the qualification of a variety of steels for their shaping by the thixoforging process. This technology requires setting up a globular microstructure inside the material during reheating to a temperature between the solidus and liquidus. As the evolution of the liquid fraction is strongly connected to the steel composition, it is useful to understand how low carbon steel could be alloyed and still thixoformable. The most critical parameter for this is the carbon content. In this study, a theoretical analysis of the phase evolution during the reheating has been performed on the MT Data software to investigate the influence of alloying elements. These first results have been confirmed by Differential Thermal Analysis and by inductive heating experiments on steel slugs. Finally, some parts have been shaped using a thixoforming tool mounted on a hydraulic press. Micrographs of reheat ed slugs as well as of actual parts are also presented in this paper.