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1

Analysis of Inorganic Binder Bridges Destruction after Thermal Load

Vaskova I., Conev M.

Archives of Foundry Engineering

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2019

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iss. 2

25--28

EN

Recently, the use of inorganic binders cured by heat as a progressive technology for large scale production of cores is widely discussed topic in aluminium foundries. As practical experiences show, knock-out properties of inorganic binders were significantly increased, although they cannot overcome organic based binder systems. This paper contains information about hot curing processes based on alkali silicate and geopolymer binder systems for core making. Main differences between hot cured geopolymers and hot cured alkali silicate based inorganic binders are discussed. Theory of geopolymer binder states, that binder bridge destruction is mainly of adhesive character. The main aim of this research paper was to examine binder bridge destruction of alkali silicate and geopolymer binder systems. In order to fulfil this objective, sample parts were submitted to defined thermal load, broken and by using SEM analysis, binder bridge destruction mechanism was observed. Results showed that geopolymer binder system examined within this investigation does not have mainly adhesive destruction of binder bridges, however the ratio of adhesive-cohesive to cohesive destruction is higher than by use of alkali silicate based binder systems, therefore better knock-out properties can be expected.

2

Technological Properties of Moulding Sands with Geopolymer Binder for Aluminium Casting

Vaskova I., Conev M., Hrubovčáková M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 4

45--49

EN

The use of environmentally friendly inorganic binders and new technologies for cores production is widely discussed topic in recent years. This paper contains information about new hot curing process for core making with alumina-silicate based inorganic binders – geopolymers. Main differences between hot cured geopolymers and hot cured alkali silicate based inorganic binders are discussed. The main objective of this research paper was to investigate basic technological properties of geopolymer binder system such as strength, compaction, storage ability and knock-out properties. For this purpose, three mixtures with different powder additives were prepared and tested in laboratory conditions using specific methods. Strength properties evaluation showed sufficient levels as well as knock-out properties measurement, even with additives B and C originally designed for the use with alkali silicate based two component binder systems. Additives B and C were considered compatible with geopolymer binders after casting production trial results. Storage ability of geopolymers seems to be more sensitive than of alkali silicate based binders in the same tested conditions. Mixtures with geopolymer binder showed 20% more decrease of strength compared to alkali silicate binders after 24 hours in conditions of 25 °C and 65 %RH.

3

The Influence of Using Different Types of Risers or Chills on Shrinkage Production for Different Wall Thickness for Material EN-GJS-400-18LT

Vaskova I., Conev M., Hrubovcakova M.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 2

131--136

EN

In modern times there are increasing requirements for products quality in every part of manufacturing industry and in foundry industry it is not different. That is why a lot of foundries are researching, how to effectively produce castings with high quality. This article is dealing with search of the influence of using different types of risers or chills on shrinkage cavity production in ductile iron castings. Differently shaped risers were designed using the Wlodawer´s modulus method and test castings were poured with and without combination of chills. Efficiency of used risers and chills was established by the area of created shrinkage cavity using the ultrasound nondestructive method. There are introduced the production process of test castings and results of ultrasound nondestructive reflective method. The object of this work is to determine an optimal type of riser or chill for given test casting in order to not use overrated risers and thus increase the cost effectiveness of the ductile iron castings production.

4

Opening Material as the Possibility of Elimination Veining in Foundries

Hrubovčáková M., Vaskova I., Benkova M., Conev M.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 3

157--161

EN

The main bulk density representation in the molding material is opening material, refractory granular material with a particle size of 0.02 mm. It forms a shell molds and cores, and therefore in addition to activating the surface of the grain is one of the most important features angularity and particle size of grains. These last two features specify the porosity and therefore the permeability of the mixture, and thermal dilatation of tension from braking dilation, the thermal conductivity of the mixture and even largely affect the strength of molds and cores, and thus the surface quality of castings. Today foundries, which use the cast iron for produce of casts, are struggling with surface defects on the casts. One of these defects are veining. They can be eliminated in several ways. Veining are foundry defects, which arise as a result of tensions generated at the interface of the mold and metal. This tension also arises due to abrupt thermal expansion of silica sand and is therefore in the development of veining on the surface of casts deal primarily influences and characteristics of the filler material – opening material in the production of iron castings.

5

Burrs from Cores Produced by Cold-Box- Amine Method and Possibility of their Elimination in Eurocast Košice s.r.o. Company

Vaskova I., Hrubovcakova M.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 1 spec.

115--120

EN

Foundry industry belongs toward key branch with important meaning for different manufacturing industries. Liquid metal is casting in foundry, which makes cast stock with weight from several grams till several ton [1]. To achieve asking qualities of the product is needed know abundance technological a technical process and progress, but in spite of long – term development foundry industry there occur some question marks, that need answer. Characteristic defect castings of ferrous alloys, which often accompanies the use of amine - Cold box cores are flash gutters. Survey, it was found that 77 % of those surveyed foundries have problems with burrs, 71 % foundries solves this problem (or try to tackle) protivýronkovými ingredients in nuclear and molding compounds , but only 29 % considered their "antivýronkovú" method for successful and favorable.

6

Physico-Chemical Ways of Improving Oxygen Converter Lining

Dzuro J., Vaskova I., Lokaj J.

Archives of Foundry Engineering

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2014

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Vol. 14, iss. 1 spec.

205--208

EN

This paper is a file of analytical information with intent to summarize so far known knowledge and to anticipate new development and possibilities of improving oxygen converter lining. Technological methods currently used in steel production put high requirements for the quality parameters of used refractory building materials. The article pursues the analysis of balance thickness of the magnesium-carbon refractory lining of basic oxygen furnace during the campaign. Development and innovation of the technologies of steel production is also reflected in increment of the requirements for magnesium-carbon refractory materials for basic oxygen furnace linings. Permanent increment in steel production has substantial influence on the refractory materials consumption in the worldwide scale. Specific methods proceedes during refining process of scrap material as quick temperatures alternation, changes in slag composition or impacts of heavy pieces of scrap material, influences destructively the basic lining of basic oxygen furnace. The static crucible corrosion test, as a simple experiment, is very useful for study of these processes because a direct observation of refractory – slag reactions in real systems is impossible. For that reason, corrosion crucible tests were adapted so that carbon basic refractories was isolated from the atmosphere by high alumina cast able cover. For such reason the high accent is put to the charge of refractory lining during the campaign which is connected with permanent increment of gunning repair refractory materials consumption. Continual increment of refractory bricks quality leads to the prolongation of time of the basic oxygen furnace campaigns.

7

Vplyv zvyšovania ocel'oveho šrotu vo vsadzke na mechanicke vlestnosti a štruktúru liatiny

Bobok L., Futaš P., Vaskova I.

Archiwum Odlewnictwa

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2004

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R. 4, nr 11/1

59--63

SK

Liatina s gulockovym grafitom (LGG) si nasla od polovice 20. storocia svoje miesto na ukor liatiny s lupienkovym grafitom (LLG) a takmer celkom vytlacila temperovanu liatinu. Nast vyroby LGG v priemyselne vyspelych statoch Europy [...]

EN

The iron casting in the long term keep up primacy the cast stock to base of iron. The cast stock from spheroidal graphite cast iron have technical and technological properties. Economic development in at the manufacturing department force the entrepreneur and manufacturer to rationalization producing at therely decreasing manufacturing costs. In term of manufacturing costs the world-wide trend take off on the way raising share steel scrap on the production of technology rises. The intention of study was finding out the effect various changing composition batch, especially steel scrap to consequential properties of spheroidal graphite cast iron.