This paper presents the results of research which is part of studies
carried out under the project POIG.01.01.02-00-015/09 "Advanced
Materials and Technologies", one of the aims of which is to introduce new,
environment-friendly, inorganic binders to the production of castings from
non-ferrous metals. The paper presents the results of research on the
management of waste moulding sands prepared
according to the new technology, including their multiple reclamation and
management of post-reclamation waste. Studies of multiple
reclamation are a continuation of the preliminary research described earlier.
The programme of the studies described in this paper also
included validation of the results under industrial conditions.
Due to the presence of harmful substances in resins those mould sands may
be hazardous to the natural environment and workers. The
general assessment of harmfulness of sands used for molds and cores
encompasses 2 basic points: emission of hazardous substances during
processes of preparing sands, pouring mold with liquid metals (high
temperatures), cooling and shaking-out; possibility of washing out
hazardous substances from used sands to the environment, during storage or
economic use outside foundries. We present the results of research on the
emission of BTEX compounds from mould sands with phenolic resins during
pouring liquid metal of different temperature (cast iron and Al alloy).
The research was conducted according to the original method prepared by
the authors, which has been used for years in cooperation with various
foundries (Poland, abroad).
More and more foundry plants applying moulding sands with water-glass or
its substitutes for obtaining the high-quality casting surface at the
smallest costs, consider the possibility of implementing two-layer moulds,
in which e.g. the facing sand is a sand with an organic binder (no-bake
type) and the backing sand is a sand with inorganic binder. Both kinds of
sands must have the same chemical reaction. The most often applied system
is the moulding sand on the water-glass or geopolymer bases – as the
backing sand and the moulding sand from the group of self-hardening sands
with a resol resin – as the facing sand. Investigations were performed for
the system: moulding sand with inorganic GEOPOL binder or moulding sand
with water glass (as a backing sand) and moulding sand, no-bake type, with
a resol resin originated from various producers: Rezolit AM, Estrofen,
Avenol NB 700 (as a facing sand). The LUZ apparatus, produced by Multiserw
Morek, was adapted for investigations. A special partition with cuts was
mounted in the attachment for making test specimens for measuring the
tensile strength. This partition allowed a simultaneous compaction of two
kinds of moulding sands. After 24 hours of hardening the highest values
were obtained for the system: Geopol binder - Avenol resin.
In this paper the effects of titanium addition in an amount up to 0.13
wt.% have been investigated to determine their effect on the
microstructure and mechanical properties of Thin Wall Vermicular Graphite Iron
Castings (TWVGI). The study was performed for thinwalled iron castings
with 3-5 mm wall thickness and for the reference casting with 13 mm.
Microstructural changes were evaluated by analyzing quantitative data sets
obtained by image analyzer and also using scanning electron microscope
(SEM). Metallographic examinations show that in thin-walled castings there
is a significant impact of titanium addition to vermicular graphite
formation. Thinwalled castings with vermicular graphite have a homogeneous
structure, free of chills, and good mechanical properties. It may
predispose them as a potential use as substitutes for aluminum alloy
castings in diverse applications.
This publication describes research on the course of the process of
cross-linking new BioCo polymer binders - in the form of water-based
polymer compositions of poly(acrylic acid) or poly(sodium
acrylate)/modified polysaccharide - using selected physical and chemical
factors. It has been shown that the type of cross-linking factor used
influences the strength parameters of the moulding sand. The crosslinking
factors selected during basic research make it possible to obtain sand
strengths similar to those of samples of sands bonded with commercial
binders. Microwave radiation turned out to be the most effective
cross-linking factor in a binder-matrix system. It was proven that
adsorption in the microwave radiation field leads to the formation of
polymer lattices with hydrogen bonds which play a major role in
maintaining the formed cross-linked structures in the binder-matrix
system. As a result, the process improves the strength parameters of the
sand, whereas the hardening process in a microwave field significantly
shortens the setting time.
Magnesium alloys due to their low density and high strength-to-weight
ratio are promising material for the automotive and aerospace industries.
Many elements made from magnesium alloys are produced by means of sand
casting. It is essential to investigate impact of the applied mould
components on the microstructure and the quality of the castings. For the
research, six identical, 100x50x20mm plates has been sand cast from the
Elektron 21 magnesium casting alloy. Each casting was fed and cooled in a
different way: one, surrounded by mould sand, two with cast iron chills
20mm and 40mm thick applied, another two with the same chills as well as
feeders applied and one with only the feeder applied. Solid solution grain
size and eutectics volume fraction were evaluated quantitatively in
Met-Ilo program, casting defects were observed on the scanning electron
microscope Hitachi S3400N. The finest solid solution grain was observed in
the castings with only the chills applied. Non metallic inclusions were
observed in each plate. The smallest shrinkage porosity was observed in
the castings with the feeders applied.
Due to the presence of harmful substances in resins those mould sands may
be hazardous to the natural environment and workers. The
general assessment of harmfulness of sands used for molds and cores
encompasses 2 basic points: emission of hazardous substances during
processes of preparing sands, pouring mold with liquid metals (high
temperatures), cooling and shaking-out; possibility of washing out
hazardous substances from used sands to the environment, during storage or
economic use outside foundries. We present the results of research on the
emission of BTEX compounds from mould sands with phenolic resins during
pouring liquid metal of different temperature (cast iron and Al alloy).
The research was conducted according to the original method prepared by
the authors, which has been used for years in cooperation with various
foundries (Poland, abroad).
The paper present the examination results concerning mechanical
properties of castings made of AlSi7MG alloy in correlation both with
the most significant squeeze casting parameters and with the modification
treatment. Experiments were planned and held according to the
2
3
factorial design. The regression equations describing the influence of the
squeeze pressure, the mould temperature, and the quantity
of strontium modifier on the strength and elongation of the examined alloy
were obtained. It was found that the main factor controlling
the strength increase is the squeeze pressure, while the plasticity (A5
) of the alloy is affected most advantageously by modification.
The application of modification treatment in squeeze casting technology
enables for production of the slab-type castings made of AlSi7Mg
alloy exhibiting strength at the level of 230 MPa and elongation exceeding
14%.
The Mg-RE alloys are attractive, constructional materials, especially
for aircraft and automotive industry, thanks to combination of low
density, good mechanical properties, also at elevated temperature, and
good castability and machinability. Present paper contains results of
fatigue resistance test carried out on Elektron 21 magnesium alloy,
followed by microstructural and fractographical investigation of
material after test. The as-cast material has been heat treated
according to two different procedures. The fatigue resistance test has
been conducted with 106 cycles of uniaxial, sine wave form stress
between 9 MPa and 90 MPa. Fractures of specimens, which ruptured during
the test, have been investigated with scanning electron microscope. The
microstructure of specimens has been investigated with light microscopy.
Detrimental effect of casting defects, as inclusions and porosity, on
fatigue resistance has been proved. Also the influence of heat
treatment's parameters has been described.
The new investigation method of a permeability of ceramic moulds applied
in the investment casting technology, is presented in the paper.
Some concepts of performing permeability measurements are shown.
Investigations in which the influence of the solid phase fraction in
the liquid ceramic moulding sand (LCMS) on a permeability of a multi-layer
ceramic mould were performed and discussed. The
permeability was estimated during two the most important stages of the
technological process: in the first – after wax melting and in the
second – after mould annealing. Also an influence of the matrix grain sizes
(material for sprinkling) on a ceramic mould permeability was
estimated.
Bending strength, thermal and electric conductivity and microstructure
examinations of Cu based composite materials reinforced with
Saffil alumina fibres are presented. Materials were produced by squeeze
casting method applying the designed device and specially
elaborated production parameters. Applying infiltration pressure of 90MPa and
suitable temperature parameters provided manufacturing of copper based
composite materials strengthened with Saffil alumina fibres
characterized by the low rest porosity and good fibre-matrix interface.
Three point bending tests at temperatures of 25, 100 and 300ºC were
performed on specimens reinforced with 10, 15 and 20% of Saffil fibres.
Introduced reinforcement effected on the relatively high bending
strengths at elevated temperatures. In relation to unreinforced Cu
casting strength of composite material Cu – 15vol.% Saffil fibres
increase by about 25%, whereas at the highest applied test temperature
of 300o C the improvement was almost 100%. Fibres by strengthening of
the copper matrix and by transferring loads from the matrix reduce its
plastic deformation and hinder the micro-crack developed during bending
tests. Decreasing of thermal and electrical conductivity of Cu after
incorporating fibres in the matrix are relatively small and these
properties can be acceptable for electric and thermal applications.
A technology of sands with water glass hardened by liquid esters is a
cheap and ecologic method of producing moulding sands. Due
to these advantages, this technology is still very important in several
foundry plants for production of heavy iron and steel castings.
Reclamation of the mixed moulding and core sands generates significant amounts
of dusts, which require further treatments for their reuse. The results
of investigations of a pressureless granulation of dusts generated in
the dry mechanical reclamation process of the mixture consisting in app.
90 % of moulding sands from the Floster S technology and in 10 % of core
sands with phenolic resin resol type, are presented in the hereby paper.
Investigations were aimed at obtaining granulates of the determined
dimensional and strength parameters. Granules were formed from the
mixture of dusts consisting of 75 mass% of dusts after the reclamation
of sands mixture and of 25 mass% of dusts from bentonite sands
processing plant. Wetted dusts from bentonite sands were used as a
binding agent allowing the granulation of after reclamation dusts
originated from the mixed sands technology.
Determined was quantitative effect of nickel equivalent value on austenite
decomposition degree during cooling-down castings of Ni-MnCu cast iron.
Chemical composition of the alloy was 1.8 to 5.0 % C, 1.3 to 3.0 % Si, 3.1
to 7.7 % Ni, 0.4 to 6.3 % Mn, 0.1 to 4.9 % Cu, 0.14 to 0.16 % P and 0.03
to 0.04 % S. Analysed were castings with representative wall thickness 10,
15 and 20 mm. Scope
of the examination comprised chemical analysis (including WDS), microscopic
observations (optical and scanning microscopy, image analyser), as well as
Brinell hardness and HV microhardness measurements of structural
components.
The possibility of controlling the solidification and cooling time of
castings creates prospects of improving their structure and by the same
their properties. Thermal properties of the mould constitute therefore
an important factor which is necessary to consider while seeking for the
mentioned improvement. The presented work illustrates the method of
determining some basic thermal coefficients of moulding material, i.e.
the coefficient of temperature equalisation a2, known also as the
temperature diffusivity, and the heat accumulation coefficient b2, which
characterises the ability of moulding material to draw away the heat
from a casting. The method consists in experimental determining the
temperature field within the mould during the processes of pouring,
solidification and cooling of the casting. The performed measurements
allow for convenient and exact calculations of the sought-after
coefficients. Examinations were performed for the oil bonded moulding
sand of trade name OBB SAND ‘E’. The experiment showed that the obtained
value of b2 coefficient differs from the value calculated on the basis
of theoretical considerations available in publications. Therefore it
can be stated that theoretical calculations of the heat accumulation
coefficient are thus far not sufficient and not quite reliable, so that
these calculations should be verified experimentally.
Organic binders applied in foundry plants based on synthetic resins,
from the one side influence obtaining the required technological
properties by the moulding sand and – in consequence – obtaining good quality
castings, and on the other side are the source of volatile
organic compounds (VOC). Together with synthetic resins their hardeners, which
although added in very small amounts emit during their thermal
decomposition substances negatively influencing the natural environment,
are also used. Both, resins and hardeners only at the influence of high
temperatures accompanying moulds pouring with liquid metal generate
harmful volatile organic compounds including compounds from the BTEX
group. Investigations of the temperature influence on the kind and
amount of organic compounds formed during the thermal decomposition of
selected binders and hardeners and their mixtures allow to determine
temperature ranges the most favourable for emitting harmful substances
as well as to compare their emission from the selected materials. The
aim of this study was the determination the temperature influence on
formation substances from the BTEX group, during thermal decomposition
of the selected binder, its hardener and their mixture. The BTEX group
emission constitutes one of the basic criteria in assessing the
harmfulness of materials applied for moulding and core sands and it can
undergo changes in dependence of the applied system resin-hardener.
Investigations were carried out on the specially developed system for
the thermal decomposition of organic substances in the temperature
range: 5000 C – 13000 C, at the laboratory scale. The investigations
subject was the furan resin, its hardener and hardened furan resin. The
assessment of the emission degree of the BTEX group in dependence of the
system subjected to the temperature influence was performed, within the
studies. The temperature range, in which maximal amounts of benzene,
toluene, ethylbenzene and xylenes were emitted from tested materials –
was defined. The qualitative and quantitative analysis of the BTEX group
were carried out with using the gas chromatography technique coupled
with the mass spectrometry (GC/MS).
Substituting of ethyl silicate with ecologic sols of colloidal silica in
the investment casting technology, resulting from the increased demands
concerning environmental protection, caused the prolongation of
production cycle for precision castings produced in multi-layer
thin-walled ceramic shell moulds. Modification of Sizol 030 binder with
benzoyl peroxide, proposed in the paper, was aimed at restriction of
time needed for realization of a single layer of the shell mould, and by
the same, of such a mould as a whole. Examination of kinetics of the
drying process were held for the layers made of prepared moulding
material and the influence of binder modification on the mould curing
time was determined.
The paper summarises results of measurements of remelting area geometry,
thermal efficiency and melting efficiency
characterising the surface remelting process applied to castings of MAR-M-509
cobalt alloy. The remelting process was
carried out with the use of GTAW (Gas Tungsten Arc Welding) method in
protective atmosphere of helium, at the electric
current intensity in the range from 100 A to 300 A, and the electric arc
scanning velocity vs in the range from 200 mm/min to
800 mm/min. The effect of current intensity and electric arc scanning velocity
on geometrical parameters of remeltings,
thermal efficiency, and melting efficiency characterising the remelting
process has been determined.
The study presents the results of research aimed at the construction of
a model of the relationship between the physical properties of metal and
the types of toughening treatment and modifiers used in the modification
of BA1044 alloy.
Samples of melts were subjected to four variants of the heat treatment and to
five types of modification. Studies of the samples consisted in
measurements of five physical parameters. Consequently, it was necessary
to seek a relationship between the nine input parameters and five output
parameters. With this number of the variables and a limited number of
samples, searching for the relationships by way of statistical methods
was obviously impossible, so it was decided to create an approximate
model through the use of fuzzy logic. This study describes the process
of creating a model and presents the results of some simulation
experiments that confirm the validity of the correct approach.
The purpose of the presented experiment was to develop an effective
water glass modifier. In the conducted research, an attempt was made to
determine the effect of modifier addition on the wettability of quartz
grains, viscosity and cohesion of binder and strength Rm
U of the sand mixture. Water glass modification was carried out with, obtained
in electrochemical process [1], colloidal suspension of ZnO
nanoparticles in methanol (modifier I) or propanol (modifier II),
characterised by a constant molar concentration of c = 0.3 M. It was
demonstrated that the addition of a colloidal suspension of ZnO
nanoparticles in propanol (modifier II) had a significant effect on
wettability of quartz grains improvement without the accompanying
increase in binder viscosity. Testing the mechanical properties Rm
U of sand mixtures containing modified binder (modifier II) hardened at
ambient conditions showed an approximately 28% increase in strength
compared with the Rm U of the sand bonded with an unmodified binder.
High-vanadium cast iron is the white cast iron in which the regular
fibrous γ + VC eutectic with the volume fraction of vanadium carbide
amounting to about 20% crystallises. This paper presents the results of
studies on high-vanadium cast iron subjected to the inoculation
treatment with magnesium master alloy. The aim of this operation is to
change the morphology of the crystallising VC carbides from the fibrous
shape into a spheroidal one. The study also examines the effect of the
amount of the introduced inoculant on changes in the morphology of the
crystallising VC carbides. To achieve the goals once set, metallographic
studies were performed on high-vanadium cast iron of eutectic
composition in base state and after the introduction of a variable
content of the inoculant.
The introduction of magnesium-based master alloy resulted in the expected
changes of microstructure. The most beneficial effect was
obtained with the introduction of 1.5% of magnesium master alloy, since nearly
half of the crystallised vanadium carbides have acquired a spheroidal
shape.
The high mechanical properties of the Al-Li-X alloys contribute to their
increasingly broad application in aeronautics, as an alternative forthe
aluminium alloys, which have been used so far. The aluminium-lithium
alloys have a lower specific gravity, a higher nucleation andcrack spread
resistance, a higher Young’s module and they characterize in a high crack
resistance at lower temperatures. The aim of theresearch planned in this
work was to design an aluminium alloy with a content of lithium and other
alloy elements. The research includedthe creation of a laboratorial melt,
the microstructure analysis with the use of light microscopy, the
application of X-ray methods to identify the phases existing in the alloy,
and the microhardness test.
A proper management of sand grains of moulding sands requires knowing
basic properties of the spent matrix after casting knocking out. This
information is essential from the point of view of the proper performing
the matrix recycling process and preparing moulding sands with reclaimed
materials. The most important parameter informing on the matrix quality –
in case of moulding sands with organic binders after casting knocking out
– is their ignition loss. The methodology of estimating ignition loss of
spent moulding sands with organic binder– after casting knocking out -
developed in AGH, is presented in the paper. This method applies the
simulation MAGMA software, allowing to determine this moulding sand
parameter already at the stage of the production preparation.