Until now, the mould sand in general use in the foundry industry are based on bentonite, which resulted from the fact that a good recognition properties and phenomena associated with this material. Come to know and normalized content of montmorillonite and carbonates and their important role in the construction of bentonite, and mass properties of the participation of compressive strength or scatter. Halloysite is widely used in industry and beyond them. However, little is known about its use in the foundry in Poland and abroad. This article presents preliminary research conducted at the Foundry Department of Silesian University of Technology on this material. Will raise the question of the representation of this two materials, which contains information connected with history and formation of materials, their structure and chemical composition. In the research, the results of compressive strength tests in wet masses of quartz matrix, where as a binder is used halloysite and bentonite in different proportions.
Moulding properties of Isasa River Sand bonded with Ipetumodu clay (Ife-North Local Government Area, Osun State, Nigeria) were
investigated. American Foundry men Society (AFS) standard cylindrical specimens 50mm diameter and 50mm in height were prepared
from various sand and clay ratios (between 18% and 32%) with 15% water content. The stress-strain curves were generated from a
universal strength testing machine. A flow factor was calculated from the inclination of the falling slope beyond the maximum
compressive strength. The result shows that the flowability of the samples increases from 18% to 26% clay content, its maximum value
was attained at 26% and then it decreases from 30% to 32% clay content. The green compressive strength, dry compressive strength and
air permeability values obtained from the mould samples were in accordance with standard values used in foundry practice. The x-ray
diffraction test shows that the sand contains silicon oxide (SiO2), Aluminium oxide (Al2O3), and Aluminium silicate (Al6Si2O13). The
mould samples were heated to a temperature of 1200 o
C to determine the sintering temperature; fussion did not take place at this
temperature. The results showed that the sand and clay mixture can be used to cast ferrous and non-ferrous alloys.
The aim of the study was to determine the applicability of a new product added to water glass-containing foundry sands hardened with
ethylene glycol diacetate. The new additive designated by the symbol "B" is a composition of aqueous solutions of modified polyalcohols,
improving the sand knocking out properties. The scope of studies included testing various mechanical and technological properties
of foundry sand mixtures, such as permeability, friability, life cycle of cores and knocking out properties.
In the technological studies, two types of water glass with different values of the silica modulus and density, designated as R145 and R150,
were used. Moulding sands were prepared with the additive "B". For comparison, reference sands with water glass but without the additive
"B" were also made. In Part I of the article, the results of studies of the effect of additive "B" on the properties of foundry sands with water
glass hardened by CO2 blowing were discussed.
Modern investigation methods and equipment for the quality estimation of the moulding sands matrices with organic binders, in their circulation process, are presented in the paper. These methods, utilising the special equipment combined with the authors investigation methods developed in the Faculty of Foundry Engineering, AGH the University of Science and Technology, allow for the better estimation of the matrix quality. Moulding sands systems with organic binders require an in-depth approach to factors deciding on the matrix technological suitability as well as on their environmental impact. Into modern methods allowing for the better assessment of the matrix quality belongs the grain size analysis of the reclaimed material performed by means of the laser diffraction and also the estimation of the moulding sand gas evolution rate and identification of the emitted gases and their BTEX group gases content, since they are specially hazardous from the point of view of the Occupational Safety and Health.
Using the available analytical methods, including the determination of chemical composition using wavelength-dispersive X-ray
fluorescent spectroscopy technique and phase composition determined using X-ray diffraction, microstructural observations in a highresolution
scanning microscope equipped with an X-ray microanalysis system as well as determination of characteristic softening and
sintering temperatures using high-temperature microscope, the properties of particular chromite sands were defined. For the study has been
typed reference sand with chemical properties, physical and thermal, treated as standard, and the sands of the regeneration process and the
grinding process. Using these kinds of sand in foundries resulted in the occurrence of the phenomenon of the molding mass sintering.
Impurities were identified and causes of sintering of a moulding sand based on chromite sand were characterized. Next, research methods
enabling a quick evaluation of chromite sand suitability for use in the preparation of moulding sands were selected.
The cumulative results of investigations of the possibility of using the reclaimed materials after the mechanical, thermal or
mechanical-thermal reclamation for making cores by means of the blowing method in the alkaline CO2 technology, are
presented in the paper. Three kinds of spent sands: with furfuryl resin, bentonite and alkaline phenolic resin, obtained from
the foundry, were subjected to three kinds of reclamation: mechanical, thermal and combined mechanical-thermal, applying
for this aim adequate experimental devices. The obtained reclaims were assessed with regard to the degree of the matrix
liberation from the determined binding material. Reclaims of moulding sands with binders of the form of resin were assessed
with regard to ignition loss values and pH reaction, while reclaims of moulding sands with bentonite with regard to the
residual clay content and pH value. In all cases the results of the performed sieve analyses were estimated and the average
characteristic diameter dl was determined. The reclaimed matrix was applied as a full substitute of the fresh high-silica sand in typical
procedures of preparing core sands used for making shaped samples for bending strength investigations, Rg
u
.
The aim of the hereby paper is to present the developed model of determining the volume and surface porosity based on the main fraction
of polifractional materials, its experimental verification and utilisation for the interpretation of effects accompanying the formation of a
moulding sand apparent density, porosity and permeability in the blowing processes of the core and moulds technology.
The results of testing the strength properties of experimental ceramic materials containing spending moulding sand after initial mechanical reclamation as a material for subsequent layers of the stucco composition were presented. Tests were carried out on spent moulding sands from various foundry technologies, i.e. sand with furfuryl resin and sand with hydrated sodium silicate. The spent, agglomerated moulding sand has undergone a crushing process. Next, the required granular fractions used for individual layers of the stucco material were separated. Ceramic samples, in which the spent moulding sand was a substitute for fresh silica sand in successive layers of the stucco composition, were prepared. As a reference material, identical ceramic samples were used but with all layers made from the fresh silica sand. Samples prepared in this way were used to determine the bending strength of ceramic materials in the temperature range from 20 to 900ºC. The obtained values of the bending strength have demonstrated that spent moulding sand can be used in investment casting with no adverse effect on the strength of ceramic materials.
It was found that the addition of carbon fibers (CFs) does not affect the crosslinking process in the microwave radiation (800 W, 2.45
GHz) of the BioCo2 binder, which is a water solution of poly(acrylic acid) and dextrin (PAA/D). It has influence on BioCo2 thermal
properties. The CFs addition improves the thermostability of a binder and leads to the reduction of gas products quantity generated in the
temperature range of 300-1100°C (TG-DTG, Py-GC/MS). Moreover, it causes the emission of harmful decomposition products such as
benzene, toluene, xylene and styrene to be registered in a higher temperatures (above 700°C). BioCo2 binder without CFs addition is
characterized by the emission of these substances in the lower temperature range. This indicates the positive effect of carbon fibers
presence on the amount of released harmful products.
The selected technological tests (permeability, friability, bending strength, tensile strength) have shown that the moulding sand with the
0.3 parts by weight carbon fibers addition displays the worst properties. The addition of 0.1 parts by weight of CFs is sufficient to obtain a
beneficial effect on the analyzed moulding sands properties. The reduction of harmful substances at the higher temperatures can also be
observed.
Bentonite is clay rock, which is created by decomposition of vulcanic glass. It is formed from mixture of clay minerals of smectite group,
mainly montmorillonite, beidellite and nontronite. Its typical characteristics is, that when in contact with water, it intensively swells. First
who used this term was W.C. Knight in 1887. The rock had been named after town Fort Benton in American state Montana. For its
interesting technological properties and whiteness has wide technological use. Bentonite is selectively mined and according to its final use
separately modified, which results in high quality product with specific parameters.
In the beginning of 21st century belong bentonite moulding mixtures in foundry to always perspective. Mainly increased ratio of ductile
cast iron castings production cannot be ensured without the need of quality bentonite. Great area of scope remains to further research of
moulding materials, which return also to bentonite producers.
The paper presents the results of laboratory tests into the effects of moisture and the content of two types of bentonite on dielectric properties of moulding sand. The use of electromagnetic waves in foundry industry is becoming more and more popular, which provides to some extent alternatives to conventional drying methods. Experimental studies published so far have shown the validity of using microwaves for drying classic moulding sands with bentonite. However, these studies lack data on the effect of moisture or bentonite content in moulding sand on the real component ε' or imaginary component ε'' of the relative complex electrical permittivity. The presented results may become in the future the basis for the evaluation of the composition of moulding sands, taking into account the phenomena occurring under the influence of electromagnetic field, which directly translates into the quality of the castings made and may constitute an attempt to develop a mathematical model of electric properties of moulding sands.
en
pl
