Development of a Hot Tear Indicator for Use in Casting Simulation

A hot tear indicator based on the physics of solidification and deformaion is presented. This indicator is derived using available data from computer simulation of solidification and solid deformation. Hot tears form when the mushy zone is starved of liquid feeding and deformed in tension. The unfed tensile deformation causes a small additional porosity. A physical model based on mass balance is developed to find the additional porosity formed. This additional porosity or porosity due to solid deformation (PSD) is a locator for initiation sites for hot tears in the casting, not a full tear prediction. By evaluating this quantity on the whole geometry, an indicator consistent with physical intuition and past experimental results is found. Using a simulation study of hot tear castings developed in SFSA literature, conclusions are drawn about the usefulness of this indicator. In summary, reducing the strain in the casting, increasing the feeding of the section, decreasing the carbon content from 0.3% to 0.15%, decreasing the sulfur and phosphorus content from 0.08% combined to 0.02%, and eliminating core restraint all decrease the hot tear tendency.