Development of high pressure die casting dies with internal refrigeration and sensors with reinforced cast steel

High Pressure Die Casting (HPDC) dies are nowadays manufactured with high quality forged steels, as the H11 and H13 steels. Cavities are made by electrical discharge machining (EDM) or by high speed milling, with a high percentage of metal loss in these operations. The average life of a standard aluminium HPDC die is about 125.000 injections, and the total price of tooling can represent around up to the 30% of the total price of the finished part. Refrigeration circuits have simple configurations, due to that they are commonly produced by drilling the die with straight holes connected between them. They are also limitations in the distances and minimum diameters of holes. Sensors are also placed where the geometry of the die permits an easy machining of location holes. In order to obtain complex figures, several new rapid prototyping methods have been developed, including sometimes customized internal circuits, as for example the laser sintering, and also for decreasing the die lead time (around 12 weeks for a standard die). However, there is a clear limitation in the life of the die produced by this technique, from several parts to thousands. A new method to obtain directly semi-finished high pressure die casting dies in a steel of higher mechanical properties and with the refrigeration circuits and sensors embedded into it is described in this paper. The method consists in produce a molten steel alloy with micro-nano special ceramic particles inserted in it, and cast the composite material in sand moulds of the desired geometry having placed properly designed refrigeration and sensor circuits. The resultant solidified near-net shape die, of steel reinforced with hard and refractory ceramics and with the cooling tubes and sensors embedded into it, is then heat treated and finished, having a use-life and a productivity about 50% and 10% higher, respectively.