Wet to Dry—Refractory Coating Control for Precision PUCB Sands

Archives of Foundry Engineering

“…Using a sample of sand of 50 mm diameter and 8 mm thickness, the thermal distortion tests can be used to simulate a specific temperature setting; for example 760°C for aluminum, 1210°C for brass, and 1375°C for cast iron, with specimen loading from 3,5 to 5N. The deformation (a concavity related to the loss of mass) is determined using a 3D scanner [19,20].…”

Foundry Coating Technology: A Review

“…Higher Baume´ number indicates higher viscosity. ρ = density of coating ρ´ = density of refractory particle material r = radius of the refractory particle (assuming a spherical particle) It was also reported in [47] that Baume when performed in a controlled laboratory environment tracks well certain coating properties, but fails to identify the g = acceleration due to gravity The stability of small particles is surprising, since surface tension leads to very high pressure differences across surfaces with small radii of curvature. For a particle of radius r, density ρ, and relative molar mass M, with surface tension γ, the pressure difference across the curved surface, p r, compared to that across a flat surface, p o , is given by the Kelvin equation.…”

“…To date no reliable non-destructive test is being applied by the foundry industry to measure the consistency of the coating layer thickness applied on the cores or moulds. In some tests, the cores are sectioned and the measurements were taken using a microscope [47,48].…”

“…A normal level of penetration is 2 -4 sand grains [44]. It was reported in [47], that this is not the most precise methodology because sand grain sizes differ from one foundry to the other. Moreover, a batch of foundry sand has a known distribution of a variety of grain sizes within it, which also makes using sand grain count as a measuring system inadequate.…”

“…As coating penetration increases, the thickness of the proud layer decreases while the reverse is the case if the proud layer increases [48]. Thermal ex-pansion increases with the thickness of the proud coating layer (the layer on the surface of the substrate) [47]. Therefore, an optimum proud layer thickness is needed to reduce the expansion defects on the casting made with these cores.…”