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Analysis of selected technological properties of green sands with starch-based additives

Drożyński D., Kurleto Ż., Kaczmarska K., Grabowska B.

Metallurgy and Foundry Engineering

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2015

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Vol. 41, no. 2

65--70

EN

This paper presents the results of determining the effect of the addition of native starch and mineral-starch mixes on selected technological properties of sands. The study was carried out on the permeability, compressive strength, and wear resistance of molding. Green sand with bentonite and silica sand was compared to green sand with the addition of Superior Standard native starch or the addition of a mineral-starch composition in the form of binder Albertine F/1. The main difference in applied starch materials is the characteristic property of native starch which is insoluble in cold water. Therefore, it was difficult to bond water added to molding sand during mixing of the ingredients in this case. However, the Albertine F/1 starch-based binder is a mixture of starch and aluminosilicates, whereas the bonding of water added into molding sand during ingredient mixing is more efficient.

PL

W artykule przedstawiono wyniki przeprowadzonych badań, które miały na celu określenie wpływu dodatku skrobi natywnej i mieszanek skrobiowo-mineralnych do klasycznych mas formier- skich na ich wybrane właściwości technologiczne. Przeprowadzone zostały badania dotyczące przepuszczalności, wytrzymałości na ściskanie oraz osypliwości mas formierskich. Masę wyjściową stanowiła masa z bentonitem na osnowie piasku kwarcowego, którą porównano z masami z dodatkiem skrobi natywnej Superior Standard oraz z dodatkiem komercyjnego spoiwa skrobiowo-mineralnego Albertine F/1. Cechą różnicującą zastosowanych materiałów skrobiowych jest to, że skrobia natywna nie rozpuszcza się w zimnej wodzie, więc w jej przypadku utrudnione jest wiązanie wody wprowadzonej do masy podczas mieszania składników. Natomiast spoiwo skrobiowe Albertine F/1 jest mieszaniną skrobi i glinokrzemianów, dzięki czemu wiązanie wody wprowadzonej do masy podczas mieszania składników okazuje się bardziej wydajne.

2

Studies on Aluminosilicate of Palygorskites Group Used as a Binder in Green Sands System

Grabowska B., Drożyński D., Kaczmarska K., Mrówka N.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 1 spec.

31--36

EN

The possibility of application of aluminosilicate from the palygorskite (attapulgite) group as a potential substitute for bentonite in green sand system application were evaluated. The effectiveness of the application of this aluminosilicate as a binder in sand grains was determined based on the results of the determination flowability, apparent density, permeability, compacability, wear resistance and compressive, tensile and shear strength of the green sands with attapulgite participation or with a mixture of bentonite-attapulgite. The results with the properties obtained for the green sand bonded by bentonite were compared. Based on these results, it was found that attapulgite as a main binder material in the green sand does not guarantee the respective properties of moulding (e.g. it was observed low green strength properties, high apparent density of mixture, low compaction and very low wear resistance). It was recognized that the natural form of attapulgite require modification in order to obtain the appropriate properties of moulding sands, which is the subject of future work within the scope of the development application of aluminosilicate in foundry industry.

3

Analysis of Selected Properties of Green Sands with Modified Starch-based Additives

Kaczmarska K., Grabowska B., Drożyński D.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3 spec.

127--131

EN

The aim of this study was the preliminary assessment the effectiveness of application of sodium carboxymethyl starch (CMS-Na) as an additives to green sands with bentonite. Two modified starches CMS-Na having a low and a high degree of substitution (DS), 0.2 and 0.9 respectively, were chosen for preparing moulding sands. Influence of modified starch with different DS on the properties of the green sand was determined based on the results of the determination: apparent density, permeability, free flowability, friability and compressive strength, tensile and shear green sands with the addition of starch. The properties of the starch without starch-based additives were compared with the properties of green sand containing in the composition of CMS-Na with different degree of substitution.

4

Influence green sand system by core sand additions

Špirutová N., Beňo J., Bednářová V., Kříž J., Kandrnál M.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 1

105-110

EN

Today, about two thirds of iron alloys casting (especially for graphitizing alloys of iron) are produced into green sand systems with usually organically bonded cores. Separation of core sands from the green sand mixture is very difficult, after pouring. The core sand concentration increase due to circulation of green sand mixture in a closed circulation system. Furthermore in some foundries, core sands have been adding to green sand systems as a replacement for new sands. The goal of this contribution is: 'How the green sand systems are influenced by core sands?" This effect is considered by determination of selected technological properties and degree of green sand system re-bonding. From the studies, which have been published yet, there is not consistent opinion on influence of core sand dilution on green sand system properties. In order to simulation of the effect of core sands on the technological properties of green sands, there were applied the most common used technologies of cores production, which are based on bonding with phenolic resin. Core sand concentration added to green sand system, was up to 50%. Influence of core sand dilution on basic properties of green sand systems was determined by evaluation of basic industrial properties: moisture, green compression strength and splitting strength, wet tensile strength, mixture stability against staling and physical-chemistry properties (pH, conductivity, and loss of ignition). Ratio of active betonite by Methylene blue test was also determined.

5

Efficiency of additives of the polysaccharide type on physical properties of bentonite mixtures

Beňo J., Jelínek P., Špirutová N., Mikšovský F.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 1

5-8

EN

The addition of polysaccharide additives generally aims at improving some important physical properties of bentonite mixtures, above all the stability of moulds against the water loss and prevention of surface defects of castings. Polysaccharide products of inland and foreign production were checked in mixtures of two bentonites of the Czech provenance with the same montmorillonite content. The attention was paid in particular to the abrasion resistance of mixtures during storing them under constant climatic conditions. Conclusions have shown the substantial influence of: the amount of the added additive, the kind and structural composition of the additive (pH of the water extract, electric conductance).