Thixoforming of Steel: Parameters and Means for Industrialization

Abstract

The deformation process of steel in the semi-solid state, or thixoforming is an alternative solution to the classical industrial processes that are the casting or the hot forging. Thixoformed steel parts are of better quality and may substitute advantageously parts realized in cast iron leading to an improvement of the rigidity, for example, but also parts in aluminium alloys obtained by the main deformation processes: for lower volume, thixoformed steel parts, keeping the same functionality, present superior mechanical properties than the parts realized in aluminium alloys. The industrial development of the steel thixoforming must be accompanied by the knowledge and the various parameters control of the process: steel grades definition and elaboration, the homogeneous high-temperature heating of the slug before deformation, conception or re-conception of the part to adapt it to the process and the practice properties, the equipment definitions which are used for the deformation operation at the semi-solid state. The handling system is also important in the thixoforming process; it is going to allow the slug transfer, at the semi-solid state, between the heating zone and the tooling or to evacuate the thixoformed part towards the mean assuring the quality heat treatment of the part. The means choice which are industrially going to ensure the process have a big importance to obtain successful production line and so, a cost reduction by “finished” part competitive with regard to processes used classically today. After the description of the applicable key points to the main parameters and the solutions used to obtain a successful product: high mechanical characteristics, near net shape or net shape geometry, no flash and limited machining operation, ... are described , The investigations finished with an approach comparing the part cost realised by thixoforming process with regard to classical processes.