Die soldering is a casting defect in which molten metal 'welds' to the surface of the tool steel die during the casting process (ref). It is the result of mechanical and metallurgical reactions at the interface between the die and the casting, and is particularly prevalent in HPDC of aluminium alloys. The 'die solder' affects the dimensional accuracy and surface finish of castings, and as a remedial measure, is regularly removed from the die.
The regular removal of aluminium die solder (ADS) is a primary cause of downtime in HPDC (ref). Whenever a die must be cleaned, production must be stopped, the die cooled and the die solder removed. ADS is currently removed by one of two techniques, both of which result in secondary problems. An ADS removal method that does not result in production down-time or secondary issues is urgently required.
Vaqua Wet Blasting (VWB) is a high volume wet blasting technique that can be configured to selectively erode a material. It was thought that VWB may be configured to remove ADS without eroding the H13 tool steel die, and used to clean the die during production. This project investigated VWB as an alternative ADS removal method and attempted to configure it for this application.
The first part of this project investigated whether VWB was effective in removing die solder. This was performed by attempting to remove die solder from die inserts and core pins by different VWB configurations. The second part of this project measured the erosion rate of H13 steel coupons when subjected to these VWB configurations. The results were combined to determine whether VWB is a viable die solder removal method, and what the optimal VWB configuration for this application is.
It was established that VWB is a viable die solder removal method. Most configurations were able to effectively remove die solder in 20-40 seconds, with H13 steel erosion rates between 3x10-2 µm/sec and 2x10-1 µm/sec. AB Glass Bead at 85 psi blasting pressure was determined as the optimum VWB configuration. It was calculated that this configuration could remove die solder from a die 1700-2400 times before 2 mm of H13 steel is eroded.