Study on the vapor-transport in sand molds and its effect on the quality of casting

Effects of pouring temperatures, moisture contents of molding sands, and the different geometries of castings on the vapor-transport time in sand molds are investigated in this study. Experimental results show that: (1) high pouring temperature shortens the vapor-transport time in sand molds. (2) in planar case for low pouring temperature (700°C), the moving velocities of condensation interface and vaporization interface are very close in spite of great difference in moisture content. (3) temperature drop of molten metal in mold cavity decreases the moving velocities of condensation zone and vaporization zone. Molding sand near mold/metal interface is slowly turning out to be dry. Molten metal is taking longer time to interact with oxide atmosphere. Casting is therefore prone to penetration defect. One-dimensional models for predicting the relationship of Tci or Tvi versus the distance from the mold/metal interface are fitted for three cases: planar, external and internal corners. Models are also extended to include the pouring temperatures of metals and the moisture contents of sand mold.