Expanded Perlite, Expanded Vermiculite and Microspheres as Fillers in New Generation Paper Pulp Mixtures Used for Contact With Liquid Metal

Abstract

Liquid metal when filling sand casting mould while pouring it out from ladle at the first moment comes across the sprue/gate system of the mould the purpose of which is to transfer liquid metal and feed the mould recess. The materials presently used for the elements of the sprue/gate systems are based on ceramics or the mixtures based on paper pulp. In this study the use of alternative mineral additions such as expanded perlite, expanded vermiculite, and microspheres as the fillers to paper pulp acquired from waste-paper for the use for the elements of mould sprue/gate systems or also other applications for the contact with liquid metal are presented. Experimental mould tube shapes made on the basis of the paper pulp based mixture patented by the authors were poured over with liquid metal. For the comparison, ceramic shapes and commercially available cellulose shapes were investigated in the same way. In order to compare the crystallization processes, a measurement of the cooling off liquid metal was carried out for all the analysed tube samples. From the so obtained metal samples metallographic microsections were made to compare cast iron microstructures. The results obtained from the investigations carried out have shown that the patented paper pulp based mixture may well be applied as an alternative material used for the elements of the sprue/gate systems for disposable sand moulds.

Gas Evolution Quantitative Analysis at a Temperature of 900°C of a Cellulose Mixture Modified by Mineral Additives

“…An analysis of the temperature change shows that there is an exothermic effect for the commercially available cellulose profile and for the experimental ex6 profile, which maintains a constant temperature of the liquid metal for some time. The effect is associated with the presence of microspheres in both samples, which has also been observed in other studies [2,20,21]. …”

“…The results have shown that using a different binder in our own mixes reduces the amount of gas generated during the high-temperature thermal treatment compared to the compounds used in the commercial mix, i.e. melamine-ureaformaldehyde resins [20].…”

“…Owing to their thermal resistance [15][16][17][18][19]22], which is higher than that of the commercial mixture [2,9], materials for the pulp modification used in the study give the experimental mixtures a thermal resistance comparable to that of commercial products [20,21], while at the same time reducing gas evolution. This effect can be attributed to the temperatures characteristic of the additives used in the study.…”

“…Being materials of high thermal resistance, the additives modify the thermal resistance parameters of the cellulose-based mixture. Owing to the characteristics of this modified novel mixture, it can be considered a short-time, one-off thermal barrier for contact with liquid metal [10,14,20,21].…”

Gas Evolution Qualitative Analyses From Modified Cellulose Mixtures During Thermal Degradation in Air and Argon

“…Pure or modified, cellulose is increasingly becoming the subject of numerous scientific studies. These studies endeavor to elucidate the mechanisms and processes which take place in cellulose-based materials when external conditions, such as temperature, change [12,13,14,17,21,22,23,25,26]. A high-temperature thermal treatment of cellulose-based materials naturally results in thermal degradation associated with mass loss which turns into gaseous by-products.…”