Application of CSIR Rheocasting Technology for the Production of an Automotive Component

Abstract

The Council for Science and Industrial Research has developed and patented a rheocasting process. The process involves the preparation of semi-solid slurries from liquid metal, by controlled cooling and MHD stirring using induction coils. An industrial prototype was designed and built to test the system in an industrial environment. A semi-solid high pressure die casting cell was set up with an industrial partner and the system was tested under normal production conditions. The production cell consisted of the CSIR rheocasting system, a six axis robot, dosing furnace and 400 ton H-400SC shot controlled Bühler HPDC machine. An engine mounting bracket originally designed for liquid HPDC was redesigned for SSM forming (casting) taking into consideration the flow and thermal behaviour of semi-solid casting process, the function of the component and the required mechanical properties. Although a full production run was not completed due to an ancillary equipment failure, sufficient castings were produced to perform preliminary evaluation of the components. The processing parameters used were, die temperature of 250°C, SSM casting temperature of 580°C ±1Cº and a piston injection velocity of 0.13 m/s. Initial evaluation showed evidence of casting defects due to a combination of factors: die design/manufacture, casting parameters and poor foundry practice. From the mechanical tests it was evident that if the die design, casting parameters and foundry practice are optimized components with adequate mechanical properties can be reliably produced.