Recent innovations in the development of the "Policast" evaporative pattern process

The Policast foundry process employs gasifiable expanded polystyrene patterns buried in loose sand and has already been introduced on the industrial scale. Research has therefore been concentrated on those of its features that are still open to further improvement, though satisfactory for the needs of high-volume manufacturing. Its aim is to reduce fabrication costs, improve product quality and make the process as a whole more reliable. Three of the innovations devised and perfected for this purpose are described. The first relates to a new procedure for making the metal tools used to mould the polystyrene foam patterns, based on electroforming, i. e. the electrodeposition of metals on suitably shaped supports that have been rendered conducting. The second innovation relates to a new system for the spheroidization of cast iron. This is carried out in special small ladles located outside the mould. Even so, it is similar in concept, and in terms of quality and yield, to in-mould spheroidization. In addition It is not specific to the Policast process, but can be adapted to any automatic pouring line It is particularly effective in overcoming certain constraints associated with Policast. The third innovation consists of the array of systems used for the instrumental checking of the most critical stage of the Policast process, namely compaction of the sand. These are systems and processes suitable for both on-line checking and experiments in the work-up of new castings

Development of a new mixed (ferritic-ausferritic) ductile iron for automotive suspension parts

Weight reduction is of great significance in the automotive industry, having direct consequences in materials used in car production and their development. In this context Teksid France and Inasmet have worked to improve practical knowledge on new ferrous casting alloys, particularly ADI. This material has been validated for suspension parts, but impact test results have caused some concern: energy values obtained were higher than those for ferritic grades, but ductility, measured as deflection, was lower. To improve this property, a material with a mixed proeutectoid ferrite plus ausferrite structure has been developed. Mechanical characterization shows tensile and proof stress, together with hardness, similar to pearlitic grades, and ductility at the same level as ferritic grades. This new type of ductile iron could be used for applications where ADI is restricted owing to excessive hardness. Validation in a suspension part for the automotive industry is foreseen in the near future.Peer reviewe

Melting and Solidification Studies by Advanced Thermal Analysis of Cast Iron

A tool widely employed in foundry is measuring the melt temperature during free cooling in cups. Thermal analysis curves provide information on liquidus, eutectic, solidus temperatures and recalescence effects. More advanced analyses can be performed in the laboratory using differential devices where a temperature program is imposed to both the sample and an inert reference. The sensitivity in the detection of temperature points is enhanced and quantitative determination of the heat release during solidification, and therefore of the solid fraction, becomes feasible.In this work we have employed a high temperature differential scanning calorimeter (Setaram HTDSC) capable of reaching temperatures up to 1600 °C to follow melting and solidification of master alloys for the production of lamellar, compact graphite and spheroidal cast irons, at various heating and cooling rates under protective helium atmosphere. Binary Fe-C alloys prepared in the laboratory with composition of 4.3 wt% C were analysed as well. The solid fraction as a function of temperature is obtained by integration of the DSC traces. The correlation between thermal data obtained by HTDSC, free cooling in cups and microstructure is shown