Development of composite salt cores for foundry applications

Abstract

For the purpose of increasing the physical/mechanical properties of the cores based on inorganic salts generally destined for pre-casting the cavities and holes of the castings from non-ferrous alloys, the composite salt matrixes are preferably used. The base salt is enriched with the materials of defined properties (granulometry, heat resistance, cooling effect, heat conductivity). This contribution aims at determining the influences of individual additives on the behaviour of the cores prepared with different methods (shooting and squeezing) during a production of the castings with a high surface quality of the precast holes.

Technological and Quality Aspects of the Use of Innovative Inorganic Binders in the Production of Castings

“…Although the differences between the values of the individual parameters for the samples prepared with shooting pressures of 8 bar and 10 bar are not as pronounced as the decrease in mechanical properties. The rate of rewetting defined as moisture content decreases with increasing shooting pressure, which correlates with previously found behavior of other inorganic binders [14]. This trend was observed for both storage conditions, differing only The wear resistance of the test specimens increased by about 10% under standard conditions (decrease from 12.04% to 11.04% at 8 bar and to 11.09% at 10 bar) when stored for 72 h. While some differences are evident when stored at high relative humidity (HRH) (20.46% at 6 bar; 18.98% at 8 bar and 20.64% at 10 bar), these data are likely to be burdened with significant measurement error as the 72 h storage time under these conditions is no longer suitable for these inorganic systems and the test specimens are significantly subject to rehydration, thus significantly affecting these values.…”

“…Although the differences between the values of the individual parameters for the samples prepared with shooting pressures of 8 bar and 10 bar are not as pronounced as the decrease in mechanical properties. The rate of rewetting defined as moisture content decreases with increasing shooting pressure, which correlates with previously found behavior of other inorganic binders [14]. This trend was observed for both storage conditions, differing only in absolute values.…”

“…Test specimens with defined dimensions of 22.4 mm × 22.4 mm × 170 mm for the determination of transverse strength were produced under the same conditions (see Table 1), only at different shooting pressures (8 and 10 bar). The effect of higher shooting pressure should be reflected by a change in the relative porosity of the sample and thus reduce the potential of the sample to rehydrate, as has been found previously for selected inorganic binders [14]. The relative porosity was determined according to the Equation (2).…”

3D printing of high-strength water-soluble salt cores via material extrusion

“…The water-soluble salt cores have attracted considerable attention due to their excellent properties including high strength, low gas evolution, and good water-soluble collapsibility, which are desired for the preparation of complex hollow composite structure castings [12][13][14][15]. Liu and Gong et al [16,17] prepared KNO 3 -based water-soluble salt cores with bending strength of 42-46 MPa for zinc alloy die castings by gravity casting method.…”

3D Printing of High-Strength Water-Soluble Salt Cores Via Layered Extrusion Forming

“…The water-soluble salt cores have attracted considerable attention due to their excellent properties including high strength, low gas evolution and good water-soluble collapsibility, which are desired for the preparation of complex hollow composite structures castings [12][13][14][15]. Liu and Gong et al [16,17] prepared KNO3-based watersoluble salt cores with bending strength of 42-46 MPa for zinc alloy die castings by gravity casting method.…”