Papers by Author: Gary Savage

Abstract: Wire rod is produced by hot-rolling a bar of metal coming from a wheel/belt continuous casting process. This kind of process, e.g. Properzi, is an elaborate process in which the molten metal is poured in a cooled rotating mould formed by the groove of a wheel and closed by a belt. In order to better understand the heat transfer phenomenon and solidified bar characteristics, depending on process parameters a three dimensional thermo-mechanical model has been developed. The model, based on the finite-element method, calculates the heat transfer coefficient of the air gap at the metal-mould interface as a function of the size of the gap determined by the bar contraction and wheel and belt thermal deformations. The air gap formation due to metal shrinkage and mould deformation is the main factor which determines the heat extraction. Wheel temperature measurements with thermocouple and belt temperature measurements with an infrared system were carried out to verify model results. Attempts were also made to measure a liquid pool profile using doping with copper rich alloy. The model shows the effect of the casting temperature and the rotation speed on the air gap formation and resulting temperature and stress fields. The model can be applied to issues such as maximising wheel and belt life and minimising solidification defects.

Abstract: Globalisation of supply chains for the automotive industry has made it increasingly difficult for developed economies to compete on price alone. In Australia, Nissan Casting has adopted technologies to reduce tooling costs and improve productivity of the die casting machines which use vacuum. Nissan Casting was experiencing cracking of their dies which extended into cooling lines, causing porosity outbreaks and shortened die life. CAST developed a repair technology called CASTrepair™ which is a relatively quick, simple and inexpensive repair technique for cracked cooling lines in HPDC dies. Also Nissan Casting is an extensive user of vacuum and a major issue was identified as unscheduled machine stoppages caused by aluminium blockages in the vacuum valves. The valves were of the mechanical shut off type and when they failed to shut off quickly enough aluminium entered the valve which then had to be changed. CAST developed CASTvac™ which is essentially a three dimensional chill vent with no moving parts required as a means to stop the aluminium entering the vacuum system. CASTvac™ has proven to be very reliable in production and has significantly reduced downtimes and toolroom maintenance at Nissan Casting. These two technologies, CASTrepair™ and CASTvac™, will be explained in detail with the latest developments in the technologies and associated benefits of their adoption.

Abstract: This paper reports on the results of the castability of three MRI alloys (153A, 153M and 230D). MRI153A was found to cast best, with castings produced rated with a quality approaching AZ91. MRI230D produced the next best castings, whilst MRI153M showed the worst castability across a range of conditions. However, these alloys showed a tendency to build-up oxide in the melt transfer tube leading to melt transfer problems. This was particularly severe in MRI230D.

Abstract: This work aims to develop flow and thermal control methods for the high pressure die casting (HPDC) of very thin-walled aluminium components where thicknesses are predominantly less than 1 mm. One specific aim includes developing advanced modelling capability using CFD software to predict the complex structure of the metal flow in the die and the casting solidification. The modelling based on FLOW-3D started initially with a fluidity die study to establish several key parameters in HPDC modelling through experimental validation. A new test casting geometry has been designed in the form of a shallow tray with other features such as changes in curvature, fins and bosses. The casting thickness can be made variable in the die. The experimental work was conducted on a 250-tonne HPDC machine. Initial models of molten metal flow in the die cavity based on a runner design for casting thicknesses between 1.5 mm and 1 mm are presented. The detailed model required a very large mesh of very small elements, and more accurate physical parameters which may not have been previously available.