Abstract
The article presents the results of research aimed at examining the type of swelling material introduced into moulding or core sand to improve their knock-out properties. Tests on Slovak perlite ore (three grain sizes), Hungarian perlite ore and ground vermiculite (South Africa) were carried out. For this purpose, thermal and structural analyses (FTIR—Fourier Transform Infrared Spectroscopy), a chemical composition test (XRF-X-Ray Fluorescence), phase analysis (XRD—X-Ray Diffraction), and scanning electron microscopy (SEM—Scanning Electron Microscope) as well as final strength tests of moulding sands with the addition of perlite ore and vermiculite were carried out. The results of thermal studies were related to IR (Infrared Spectroscopy) spectra and XRD diffractograms. It has been shown that the water content in the pearlite ore is almost three times lower than in vermiculite, but the process of its removal is different. Moreover, the chemical composition of the perlite ore, in particular the alkali content and its grain size, may influence its structure. The phenomena of expansion (perlite) and peeling (vermiculite) have a positive effect on the reduction of the final sand strength and eliminate technological inconveniences (poor knocking out) that significantly limit the wide use of moulding sands with inorganic binders.
Highlights
The current state of knowledge indicates that many attempts have been made to eliminate the main technological disadvantage, which is poor knock-out property, that limits the wide use of moulding sands with inorganic binders in a foundry
The amount between the grading of the Slovak perlite ore (SP1–SP3) and the amount of of water water accumulated accumulated in in its its structure; structure; the chemical composition, in particular the alkali ratio K2 O/Na2 O, and the size of the chemical composition, in particular the alkali ratio K2O/Na2O, and the size of the the fraction may have a significant impact on the expandability of the pearlite ore
In the the case of the finest fraction at a temperature above 900 ◦ C, it is possible to create an case of the finest fraction at a temperature above 900 °C, it is possible to create an amorphous phase in the entire sample volume; amorphous phase in the entire sample volume; in the finest fraction of Slovak perlite (SP1) at the temperature above 300 ◦ C, no in the finest fraction of Slovak perlite (SP1) at the temperature above 300 °C, no changes in the phase composition were found, while above the temperature of 900 ◦ C, changes in the phase composition were found, while above the temperature of 900 reflections from the crystalline phases disappear, and the sample consists only of the
Summary
The current state of knowledge indicates that many attempts have been made to eliminate the main technological disadvantage, which is poor knock-out property, that limits the wide use of moulding sands with inorganic binders in a foundry. Many attempts have been made to improve the knockout properties with the use of various types of materials or by modifying the structure of inorganic binders, e.g., by introducing metal oxides All these measures were aimed at reducing the final strength of the moulding sand and led to an improvement in the knock-out properties [5,6,7,8,9,10,11,12,13]. A significant gap is the lack of data on the effect of perlite ore with a different grain size and type of deposit on the ability to reduce the final strength of moulding and core sand, and improve its knock-out properties. The results contained in the publication supplement the knowledge available so far
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