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Long-term Effects of Relative Humidity on Properties of Microwave Hardened Moulding Sand with Sodium Silicate

Stachowicz M., Granat K.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 3

127--132

EN

Moulding sands containing sodium silicate (water-glass) belong to the group of porous mixture with low resistance to increased humidity. Thanks to hydrophilic properties of hardened or even overheated binder, possible is application of effective methods of hydrous reclamation consisting in its secondary hydration. For the same reason (hydrophilia of the binder), moulds and foundry cores made of high-silica moulding sands with sodium silicate are susceptible to the action of components of atmospheric air, including the contained steam. This paper presents results of a research on the effect of (relative) humidity on mechanical and technological properties of microwave-hardened moulding mixtures. Specimens of the moulding sand containing 1.5 wt% of sodium water-glass with module 2.5 were subjected, in a laboratory climatic chamber, to long-term action of steam contained in the chamber atmosphere. Concentration of water in atmospheric air was stabilized for 28 days (672 h) according to the relative humidity parameter that was ca. 40%, 60% and 80% at constant temperature 20 °C. In three cycles of the examinations, the specimens were taken out from the chamber every 7 days (168 h) and their mechanical and technological parameters were determined. It was found on the grounds of laboratory measurements that moulds and cores hardened with microwaves are susceptible to action of atmospheric air and presence of water (as steam) intensifies action of the air components on glassy film of sodium silicate. Microwave-hardened moulding sands containing sodium silicate may be stored on a long-term basis in strictly determined atmospheric conditions only, at reduced humidity. In spite of a negative effect of steam contained in the air, the examined moulding mixtures maintain a part of their mechanical and technological properties, so the moulds and foundry cores stored in specified, controlled conditions could be still used in manufacture.

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Effect of Sand Base Grade and Density of Moulding Sands with Sodium Silicate on Effectiveness of Absorbing Microwaves

Stachowicz M.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 3

103--108

EN

In the paper, presented is a research on effectiveness of absorbing electromagnetic waves at frequency 2.45 GHz by unhardened moulding sands prepared of three kinds of high-silica base and a selected grade of sodium silicate. Measurements of power loss of microwave radiation (Pin) expressed by a total of absorbed power (Pabs), output power (Pout) and reflected power (Pref) were carried-out on a stand of semiautomatic microwave slot line. Values of microwave power loss in the rectangular waveguide filled with unhardened moulding sands served for determining effectiveness of microwave heating. Balance of microwave power loss is of technological and economical importance for manufacture of high-quality casting moulds and cores of various shapes and sizes. It was found that relative density influences parameters of power output and power reflected from samples of moulding sand placed in a waveguide. Absorption expressed by the parameter Pabs is not related to granularity of high-silica base: fine, medium and coarse. It was found that the semiautomatic microwave slot line supports evaluation of effectiveness of microwave absorption on the grounds of power loss measurements and enables statistic description of influence of relative density of the sandmix on penetration of electromagnetic waves in unhardened moulding sands.

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Dielectric Properties of High-Silica Sand at 2.45 GHz

Opyd B, Nowak D., Granat K.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 1 spec.

136--139

EN

In the paper, presented are measurements of permittivity (εr) and dielectric loss factor (tgδ) of high-silica moulding sand, determined at 2.45 GHz by perturbation method on a stand of waveguide resonance cavity. Determined were electrical properties of the main component of moulding sands, i.e. high-silica base, critical for their heating kinetics. The measurements were carried-out for six kinds of high-silica sand with diverse grain size distribution. Analysis of the results indicates that both permittivity and loss tangent values are similar for all kinds of high-silica moulding sand. Irrespective of their grain size analysis, neither of the examined sandmixes shows susceptibility to action of 2.45 GHz microwave field. The presented results make a ground for developing a mathematical model of microwave heating of technological systems composed of moulding sand and foundry tooling.

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Właściwości ceramicznych tworzyw porowatych z piasku kwarcowego otrzymanych metodą spiekania ziaren

Wiśniewski P.

Szkło i Ceramika

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2009

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R. 60, nr 2

26-29

PL

W pracy przedstawiono wyniki badań nad wpływem ilości spoiwa wysokotemperaturowego na właściwości ceramicznych tworzyw porowatych otrzymanych metodą spiekanych ziaren. W badaniach zastosowano piasek kwarcowy o dwóch wielkościach ziaren 0,4-0,8 mm i 0,8-1,2 mm oraz 5, 10, 15 i 20% wag. dodatku spoiwa wysokotemperaturowego. Wyznaczono gęstość, porowatość otwartą, nasiąkliwość wodną i wytrzymałość mechaniczną kształtek oraz średnią i maksymalną wielkość porów tworzyw porowatych metodą pęcherzykową i oszacowano wpływ ilości spoiwa na ww. parametry. Zwiększenie udziału spoiwa w kształtkach spowodowało zwiększenie maksymalnej i średniej wielkości porów oraz zmniejszenie ich porowatości i nasiąkliwości przy jednoczesnym wzroście gęstości względnej, a także wytrzymałości na rozciąganie i ściskanie.

EN

In this paper the results of studies on influence of high temperature binder amount on properties of porous ceramic materials were presented. In the investigations, high-silica sand characterized by a diameters: 0,4-0,8 mm and 0,8-1,2 mm, and addition of 5, 10, 15 and 20 wt. % high temperature binder in the materials were used. During research density, open porosity, water absorption, mechanical strength, maximal and average pore diameter measured by the "bubble method" of porous materials were presented. Increase of the binder amount in the samples causes increase of maximal and average pore size, increase tensile and bending strength, decrease of open porosity and water absorption of silica porous materials.

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HÜTTENES-ALBERTUS Polska - producent najwyższej jakości suszonych piasków kwarcowych i piasków powleczonych żywicą przeznaczonych dla przemysłu odlewniczego

Prawdzik S., Pietrzak A.

Przegląd Odlewnictwa

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2005

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Vol. 55, nr 3

156-161

PL

Artykuł prezentuje produkcję piasków suszonych i powleczonych żywicami. W Polsce obecnie produkuje się około kilku tysięcy ton piasku kwarcowego w ciągu roku z czego prawie połowę wytwarza firma Hüttenes-Albertus Polska. Produkcja ta odbywa się w Lublinie w budynkach byłej Odlewni Żeliwa, gdzie zainstalowano nowoczesną linię technologiczną, w skład której wchodzą: gniazdo suszenia piaski GSP-12 i linia piasków powleczonych LPO-4. W artykule Autorzy opisali parametry techniczne linii technologicznej, a także poszczególne etapy produkcji, rodzaje wytwarzanego piasku oraz badania prowadzone nad jakością piasku kwarcowego.

EN

The article presents the production of the dried and the with resins covered sands. In Poland there are produced actually some thousands tons of quartz sandyearly herein almost one half is produced by the firm Hüttenes-Albertus Polska. The buildings of former Cast Iron Foundry in Lublin are utilized for t his production. A modern technological line composed of drying centre for the sand GSP-12 and of covered sand LPO-4 production - line was installed there. In the article the technical parameter of the production line as well as the particular production stages, the kinds of sands being produced and investigations on the quartz sand quality are presented.

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Parametry stożka formowanego z piasku kwarcowego

Dzwonnik I.

Archiwum Odlewnictwa

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2001

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R. 1, nr 2

468--474

PL

Przedstawiono nowa metodę pomiaru właściwości piasków w odniesieniu do parametrów stożka nasypowego formowanego z tych materiałów. Zaproponowana metoda polega na formowaniu stożka z strugi badanego materiału spadającego z określonej wysokości H = 1000 mm na krążek o średnicy 150 mm będącego podstawę stożka nasypowego. Następnie mierzono wysokość i masę uformowanego stożka. Na zaprojektowanym i wykonanym stanowisku dokonano pomiarów parametrów stożka formowanego z piasków drobnych i grubych o zmiennej wilgotności.

EN

A new method for the determination of properties of sand and mould mixes, which is based on measuring the parameters of coning samples formed with these materials, has been presented. The proposed method consists in forming of cone with the material being poured down from the height of 1000 mm onto the cone base, which is a disk of the diameter 150 mm. The testing device, especially designed and prepared for this goal, was used to measure the height and the mass of cone formed from fine and coarse-grained sands as well as from sand mix of variable humidity.