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Notes: A semi solid thin strip continuous casting process was used to obtain 50%wtPb/50%wtSn strip by single and twin roll processing at speed of 15 m/min. A 50%wt Pb/50%wtSnplate ingot was also cast for rolling conventionally into strips of 1.4 mm thickness and 45 mm widthfor comparison with those achieved non-conventionally. This hypoeutectic alloy has a solidificationinterval and fusion temperature of approximately 31°C and 215°C respectively. The casting alloytemperature was around 280°C as measured by a type K immersion thermocouple prior to pouringinto a tundish designed to maintain a constant melt flow on the cooling slope during semi solidmaterial production. A nozzle with a weir ensures that the semi solid material is dragged smoothlyby the lower roll, producing strip with minimum contamination of slag/oxide. The temperatures ofthe cooling slope and the lower roll were also monitored using K type thermocouples. The coiledsemi solid strip, which has a thickness of 1.5 mm and 45 mm width, was rolled conventionally inorder to obtain 1.2 mm thick strip. The coiled thixorolled strip had a thickness of 1.2 mm andachieved practically the same width as the conventional strips. Blanks of 40 mm diameter were cutfrom the strips in a mechanical press, ready for deep drawing and ironing for mechanicalcharacterization. All the strips achieved from non-conventional processing had the same mechanicalperformance as those achieved conventionally. The limiting drawing ratio (LDR) achieved wasapproximately 2.0 for all strips. Microscopy examination was made in order to observe phasesegregation during processing

Notes: The aim of this work is to study the solidification conditions necessary to produce good quality/lowdefect metal alloy strip when thixorolling directly from the semi-solid state. To facilitate the studylead/tin alloys were chosen for their relatively low operating temperature. The objective is toextrapolate these findings to the higher temperature aluminium alloys. Three alloys (70%Pb-30%Sn, 60%Pb-40%Sn, 50%Pb-50%wtSn) were used particularly to study the influence of thesolidification interval. The equipment consists of a two roll mill arranged as an upper and lowerroller, where both rollers are driven at a controlled speed. The lower roller is fed with semi solidalloy through a ceramic nozzle attached to the lower end of a cooling slope. Several types of nozzleand their position at the roller were tested. This produced different solidifications and consequentlydifferent finished strip. The alloys were first cast and then poured onto the cooling slope through atundish in order to create a continuous laminar flow of slurry and uniformity of metal strip quality.The pouring was tested at different positions along the slope. The cooling slope was coated withcolloidal graphite to promote a smooth slurry flow and avoid the problem of adherence andpremature solidification. The metallic slurry not only cools along the slope but is also initiallysuper-cooled to a mush by the lower roller whilst at room temperatures, thus enabling thixorolling.It was also found that the nozzle position could be adjusted to enable the upper roller to alsocontribute to the solidification of the metallic slurry. However the rollers and the cooling slopenaturally heat up. Temperature distribution in these zones was analysed by means of threethermocouples positioned along the cooling slope and a fourth in the base of the semi solid poolwithin the nozzle. The objective being to design an optimum pouring and cooling system. Theformed strip was cooled down to room temperature with a shower of water. Microstructures of thethixorolling process were analysed. The differences in solidification conditions resulted in differingqualities of finished strip and corresponding defect types, all of which are a serious quality issue forthe rolled product