The Need for a New Approach to Soldering in High Pressure Die Casting

Soldering remains one of the most common defects in high pressure die casting (HPDC). It is most simply defined as aluminum stuck to the die surface. At ejection, the stuck aluminum gouges the casting resulting in dimensional and leaking defects. For nearly 50 years, a thermodynamics and kinetics understanding of soldering has been accepted while explicitly assuming that other mechanisms are not important. It will be shown that this thermodynamics and kinetics modeling approach cannot adequately explain three common observations in die casting foundries. First, soldering occurs much faster than the measured intermetallic growth rate based on diffusion couple experiments. Second, the alloys that are industrially observed to solder less form intermetallic phases quicker and dissolve the steel faster than alloys that solder more rapidly. Finally, the intermetallic layer is not strong enough to enable the buildup commonly observed on soldered dies. For these reasons, it is proposed that a new soldering modeling approach is required to gain a better understanding of the soldering mechanism and prevent the soldering defect in die casting.