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Gases Emission From Surface Layers of Sand Moulds and Cores Stored Under the Humid Air Conditions

Kaźnica N., Zych J., Mocek J.

Archives of Foundry Engineering

2017

Vol. 17, iss. 4

79--84

A large number of defects of castings made in sand moulds is caused by gases. There are several sources of gases: gases emitted from moulds, cores or protective coatings during pouring and casting solidification; water in moulding sands; moisture adsorbed from surroundings due to atmospheric conditions changes. In investigations of gas volumetric emissions of moulding sands amounts of gases emitted from moulding sand were determined - up to now - in dependence of the applied binders, sand grains, protective coatings or alloys used for moulds pouring. The results of investigating gas volumetric emissions of thin-walled sand cores poured with liquid metal are presented in the hereby paper. They correspond to the surface layer in the mould work part, which is decisive for the surface quality of the obtained castings. In addition, cores were stored under conditions of a high air humidity, where due to large differences in humidity, the moisture - from surroundings - was adsorbed into the surface layer of the sand mould. Due to that, it was possible to asses the influence of the adsorbed moisture on the gas volumetric emission from moulds and cores surface layers by means of the new method of investigating the gas emission kinetics from thin moulding sand layers heated by liquid metal. The results of investigations of kinetics of the gas emission from moulding sands with furan and alkyd resins as well as with hydrated sodium silicate (water glass) are presented. Kinetics of gases emissions from these kinds of moulding sands poured with Al-Si alloy were compared.

Zjawisko erozji w formach wykonywanych z mas ze spoiwami chemicznymi

Zych J., Mocek J.

Archiwum Odlewnictwa

2002

R. 2, nr 3

155--162

Wykonano badania nad określeniem odporności erozyjnej mas wiązanych spoiwami chemicznymi: żywicami furanowymi i szkłem wodnym. Zjawisko erozji w masach ze spoiwami organicznymi przebiega intensywnie szczególnie przy słabym zagęszczeniu masy i wysokiej temperaturze metalu. Formy z tych mas muszą mieć zabezpieczaną powierzchnię roboczą odpowiednią powłoką. Erozja formy ze szkłem jest mniej intensywna, ale może obejmować większe powierzchnie z uwagi na wysoką osypliwość tej masy, wymagają więc również stosowania pokryć ochronnych.

Within a framework of this work the erosive resistivity of chemical (e.g. furan resin and water-glass) bonded sand moulds was investigated. Erosion of moulding sands with organic binders is very intensive particulary in the case of low density of the moulding sand and high temperature of the poured metal. Working surface of mould made of these moulding sands should be covered with proper coating. Erosion of the mould made of sand bonded with water-glass is less intensive, but it can envelop greater area because of a larger liquidyty of that moulding sand, so in that case the protective coating should also be applicated.