Eagle Alloy, Inc. has utilized MAGMASOFT® since 2007 in the development of rigging systems for a large range of steel alloys, all cast with the shell mold and shell core process. The rigging system for the mooring socket was developed using MAGMASOFT® and the rigging produced a casting free of inclusions and shrink. However, there were other root causes for the cracks. They turned to the engineering services at MAGMA Foundry Technologies to provide assistance for what they suspected to be two possible root causes for the cracks, segregation and thermal stresses.
The original rigging and process parameters were used to establish a baseline segregation. Using MAGMAsteel, low levels of segregation were predicted across the riser contact. The simulation showed the riser and riser contact to be slightly larger than necessary, and the size of the riser and contact were reduced which also decreased the amount of segregation. Improving the yield and decreasing the segregation were positive steps towards improving the casting, but this was not the final stop in eliminating the casting cracks.
The primary root cause for the cracks was uncovered by evaluating the stresses created during cooling of the casting. The casting geometry and the rigging was symmetrical, but the entire system was filled through one side riser. The asymmetrical filling of the system produced a „cold side“ and a „hot side“ at the end of the filling with substantial and lasting effects through solidification and cooling. The maximum principal stress results confirmed a localized region of high tensile stress at the riser contact, and these stresses were higher on the hot side.