Effect of Microwave Heating on Moulding Sand Properties with Gypsum Binder

Abstract

The paper presents results of initial research on the possibility of applying microwave radiation in an innovative process of making casting moulds from silica sand, where gypsum CaSO4•2H2O was acting as a binding material. In the research were compared strengths and technological properties of moulding mixture subjected to: natural bonding process at ambient temperature or natural curing with additional microwave drying or heating with the use of microwaves immediately after samples were formed. Used in the research moulding sands, in which dry constituents i.e. sand matrix and gypsum were mixed in the ratio: 89/11. On the basis of the results of strength tests which were obtained by various curing methods, beneficial effect of using microwaves at 2.45 GHz for drying up was observed after 1, 2 and 5 hours since moisture sandmix was formed. Applying the microwaves for hardening just after forming the samples guarantees satisfactory results in the obtained mechanical parameters. In addition, it has been noted that, from a technological and economic point of view, drying the silica sand with gypsum binder in microwave field can be an alternative to traditional molding sand technologies.

Archives of Foundry Engineering

“…Plaster Gypsum: "Dolina Nidy" [16] (moisture content 4.1%) and 6 pbw. water [25][26][27][28]. The composition of the mass is consistent with the gypsum binders used in the studies on the possibility of using various types of gypsum binders as a binding material [23].…”

“…Using of elasticized, commercially available plaster gypsum "Dolina Nidy" [23,24], aims to provide the molding sand, compared to the commonly used building gypsum, favorable molding properties, especially extended setting time, important from the point of view of its use in technology mold and core.…”

“…The combination of the recommended [25], reduced water content in the molding sand [23], which should ensure its loose consistency and non-sticking to the tooling and intensive microwave drying, will ultimately guarantee the achievement of the main research objective, which is to shorten the drying time, and thus improve the mold making process and cores and its easy mechanization and / or automation.…”

“…The commercially available binder used in the research contains mainly CaSO 4 • 0.5H 2 O β-hemihydrate and CaCO 3 carbonate as well as additives modifying and regulating the setting time [23,24].…”

Archives of Foundry Engineering

“…The use of elastic, commercially available plaster gypsum [12,13] allowed, thanks to its specific features, to achieve further research objectives related to achieving favorable properties of molding sand from the point of view of its application in mold and core technology.…”