Search for: All records

Slag defects remain a persisting and prominent problem for steel foundries across the world. Slag defects are surface defects usually caused by oxides transported from the pouring ladle or formed during the initial stages of filling that are transported into the casting cavity during pouring. This study investigates the use of vortex chambers as a component of the gating system and a potential slag trapping mechanism for ferrous metals through computational modeling and experimental validations. Six vortex chamber designs were studied using 3D sand-printing (3DSP) with varying chamber thickness and inlet-outlet height difference. For experimental validation, ASTM A216 WCB steel plates were cast using these vortex chamber designs. The results were compared to a benchmark design consisting of a conventional straight runner section in place of the vortex chamber. Computational results include ingate velocity during filling, entrained air volume fraction, and free surface defect mass. Experimental results include a subsurface pore volume fraction model based on the measured ultrasonic wave speed and attenuation. The experimental results were correlated with the computational results and show strong agreement. The computational results suggest a 31% reduction in melt velocity at the ingate from one of the vortex chamber designs and confirming the reduction in turbulence and reoxidation in the melt stream. However, the experimental results suggest no significant improvement in terms of subsurface porosity for the vortex chamber designs based on previous literature. 

3D sand printing (3DSP) is a comparatively new additive manufacturing (AM) technology which has opened new opportunities for the sand-casting industry. Complex parts with intricate features that were inaccessible through the traditional mold and core making process and would take significant lead time to production can be now easily manufactured using 3DSP technology. Previous studies through numerical modeling have revealed that novel 3D riser geometries offer significant advantages during solidification of the casting by providing higher solidification time, less macro-porosity, and less piping inside the riser. This current study focuses on the experimental validation of the numerical study. Nine different riser geometries were printed as cores using 3DSP which were later installed in a larger sand mold accommodating the rigging (sprue, runners, ingates). Three novel riser shapes (ellipsoid, spherical and fusion) and one traditional cylindrical riser were explored in this study. The spherical risers were studied to understand the effect of the novel riser shape on the neck region. With three repetitions of each design (total of nine designs), a total of 27 castings were manufactured and characterized for statistical analysis. ASTM A216 WCB (wrought carbon steel, grade B) alloy was used to pour all the molds. Results from the ultrasonic tests, flexural test, and X-ray CT inspection show strong agreement with the previous FEA analysis along with 45 % yield improvement, 32 % reduction in riser neck diameter and increased mechanical strength.