Opening Material as the Possibility of Elimination Veining in Foundries

Abstract

The main bulk density representation in the molding material is opening material, refractory granular material with a particle size of 0.02 mm. It forms a shell molds and cores, and therefore in addition to activating the surface of the grain is one of the most important features angularity and particle size of grains. These last two features specify the porosity and therefore the permeability of the mixture, and thermal dilatation of tension from braking dilation, the thermal conductivity of the mixture and even largely affect the strength of molds and cores, and thus the surface quality of castings.[1] Today foundries, which use the cast iron for produce of casts, are struggling with surface defects on the casts. One of these defects are veining. They can be eliminated in several ways. Veining are foundry defects, which arise as a result of tensions generated at the interface of the mold and metal. This tension also arises due to abrupt thermal expansion of silica sand and is therefore in the development of veining on the surface of casts deal primarily influences and characteristics of the filler material -opening material in the production of iron castings.

The effect of sand quality on the bending strength and thermal distortion of chemically bonded sand cores

“…The derivatives of the investigated parameters with respect to the temperature are also presented to visualize the rate of temperature change ( Figure 8 (a)) and the rate of mass change ( Figure 8 (b)). On the DTA curve of the thermally reclaimed sand ( Figure 8 (a)), only one significant endotherm peak could be detected, which indicates the polymorphic transformation of α-quartz to β-quartz at around 573 °C [ 42 , 43 ]. It is reported [ 42 ] that β-quartz transforms into α-tridymite at around 870 °C.…”

“…On the DTA curve of the thermally reclaimed sand ( Figure 8 (a)), only one significant endotherm peak could be detected, which indicates the polymorphic transformation of α-quartz to β-quartz at around 573 °C [ 42 , 43 ]. It is reported [ 42 ] that β-quartz transforms into α-tridymite at around 870 °C. However, this transformation is highly dependent on the purity of the investigated quartz samples.…”

Effect of the Composition of Hybrid Sands on the Change in Thermal Expansion

“…The highest value of dilatation is found in monofraction sand with rounded grains. In [ 18 ], the most effective approach to prevent stress defects is to replace the sand with another sand with lower thermal expansion (deformation) values, without phase transformations [ 19 , 20 , 21 ].…”

Archives of Metallurgy and Materials

“…this sand is limited due to not satisfactory refractoriness, high thermal expansion etc. and various casting defects could be occurred [1][2][3][4][5][6]. From this point of view various non-silica sands are applied, chromite sand especially.…”