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.
Presented are results of a research on usability of an innovative reclamation process of microwave-hardened moulding sands containing
water-glass, combined with activation of binder. After each subsequent stage of reclamation, quality of the reclaimed material was
determined on the grounds of measurements of permeability and results of screen analysis. The reclaimed material was next used again to
prepare new moulding sand. The sandmix based on high-silica sand prepared with water-glass grade 145, was subject to the following
cyclical treatment operations: mixing components, consolidation, microwave hardening, cooling, heating the mould up to 800 °C, cooling
to ambient temperature, mechanical reclamation dry and wet. It was found that the used-up and reclaimed sandmix containing water-glass
is susceptible to the applied activation process of thermally reacted film of binder and, in addition, it maintains good quality and
technological properties of high-silica base. Observations of surfaces of reclaimed high-silica grains with activated film of reacted
inorganic binder were carried-out using a scanning microscope. Thanks to properly selected reclamation parameters, the high-silica base
can be reused even five times, thus reducing demand for fresh aggregate and inorganic binder.
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 longterm
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.
In this paper, the effect of changes the parameters of heat treatment on the structure and the degree of elements segregation was
determined, in the context of corrosion resistance of ductile iron Ni-Mn-Cu, containing 7.2% Ni, 2.6% Mn and 2.4% Cu. In the condition
after casting, castings of austenitic matrix and 160HBW hardness were obtained. The achieved castings were soaked at 450, 550 and
650°C for 4, 8 and 12 hours, then cooled down at the ambient air. In most cases, the heat treatment resulted in a change in the castings
matrix, had the consequence of increasing their hardness in comparison to raw castings. Increasing the temperature and prolonging soaking
time resulted in increasing the degree of transformation of austenite, while reducing the degree of elements segregation. This led to the
formation of slightly bigger number of pitting due to corrosion, but not so deep and more evenly distributed in comparison to raw castings.
Wherein the results of corrosion tests show that heat treatment of castings did not significantly change their corrosion resistance in
comparison to raw castings, in contrast to the significant increase in mechanical properties.
In recent years, an increasing interest in sandmixes containing inorganic binders has been observed. These binders, including water-glass, are harmless for the environment, neutral for humans, and relatively cheap. In spite of numerous advantages, their wide application is restricted by poor knock-out properties and problems related to rebonding. Therefore, numerous researches aimed at eliminating the disadvantages of water-glass binders are directed, among others, to modifying the structure of hydrated sodium silicate or to applying new hardening techniques. An innovative method of rapid hardening by microwave heating, permitting the restriction of the quantity of binder used and thus improving knock-out properties, meets the expectations of present-day foundries. In this paper, available information is compiled on microwave hardening of water-glass containing sandmixes; furthermore, the costs of practical application of this technology are evaluated on the grounds of the authors' own research.
The paper presents the results of preliminary research on the use of silica sands with hydrated sodium silicate 1.5% wt. of binder for the performance of eco-friendly casting cores in hot-box technology. To evaluate the feasibility of high quality casting cores performed by the use of this method, the tests were made with the use of a semiautomatic core shooter using the following operating parameters: initial shooting pressure of 6 bar, shot time 4 s and 2 s, core-box temperature 200, 250 and 300 °C and core heating time 30, 60, 90 and 150 s. Matrixes of the moulding sands were two types of high-silica sand: fine and medium. Moulding sand binder was a commercial, unmodified hydrated sodium silicate having a molar module SiO2/Na2O of 2.5. In one shot of a core-shooter were made three longitudinal samples (cores) with a total volume of about 2.8 dm3. The samples thus obtained were subjected to an assessment of the effect of shooting parameters, i.e. shooting time, temperature and heating time, using the criteria: core-box fill rate, bending strength (RgU), apparent density and surface quality after hardening. The results of the trials on the use of sodium silicate moluding sands made it possible to further refine the conditions of next research into the improvement of inorganic warm-box/hot-box technology aimed at: reduction of heating temperature and shot time. It was found that the performance of the cores depends on the efficiency of the venting system, shooting time, filling level of a shooting chamber and grains of the silica matrix used.
In the paper, an attempt is made to explain the previously observed increased effectiveness of utilising hydrated sodium water-glass grade
137 after hardening moulding sands with selected physical methods. In the modified process of preparing sandmixes, during stirring
components, water as a wetting additive was introduced to the sand-binder system. Presented are examination results of influence of faster
microwave heating and slower traditional drying of the so-prepared moulding sands on their tensile and bending strength, calculated per
weight fraction of the binder. The measurement results were confronted with SEM observations of linking bridges and with chemical
analyses of grain surfaces of high-silica base. On the grounds of comprehensive evaluation of hardened moulding sands, positive effects
were found of the applied physical process of binder dehydration and presence of the wetting additive. It was observed that introduction of
this additive during stirring, before adding the binder, improves flowing the binder to the places where durable linking bridges are created.
It was also found that the applied methods of hardening by dehydration enable creation of very durable linking bridges, strongly connected
with the sand base, which results in damages of high-silica grain surfaces, when the bridges are destroyed.
Presented are results of a research on the possibility of using artificial neural networks for forecasting mechanical and technological
parameters of moulding sands containing water-glass, hardened in the innovative microwave heating process. Trial predictions were
confronted with experimental results of examining sandmixes prepared on the base of high-silica sand, containing various grades of
sodium water-glass and additions of a wetting agent. It was found on the grounds of obtained values of tensile strength and permeability
that, with use of artificial neural networks, it is possible complex forecasting mechanical and technological properties of these materials
after microwave heating and the obtained data will be used in further research works on application of modern analytic methods for
designing production technology of high-quality casting cores and moulds.
This paper presents the results on the effects of die-casting process on the strength parameters of castings of the aluminium AlSi9Cu3 alloy
belonging to the group of EN AB-46000, made on renovated high pressure die-casting machine. Specimens for quality testing were taken
from the places of the casting most loaded during the service. The aim of a research was to prove how the new die-casting process control
capabilities influence on the tensile strength of the cast material defined as a value of the breaking force of the specimens. It has been
found that it is possible to specify a set of recommended settings valves of second (II) and third (III) phase, which are responsible for
filling the metal mould on die-casting pressure machine. From the point of view of the finished cast element, it was noticed that exceeding
the prescribed values of valve settings does not bring further benefits and even causes unnecessary overload and reduce the durability of
the mold. Moreover, it was noticed that reduction of the predetermined setting of the second phase (II) valve leads to the formation of
casting defects again.
In the paper, an attempt was made to evaluate the effect of preliminary wetting of high-silica base during preparation of moulding sands
containing a selected grade of sodium water-glass, designed for hardening by traditional drying or by electromagnetic microwaves at 2.45
GHz. In the research, some water was dosed during stirring the sandmix before adding 1.5 wt% of the binder that was unmodified sodium
water-glass grade 137, characterised by high molar module within 3.2 to 3.4. Scope of the examinations included determining the effect of
wetting the base on mechanical parameters like compression, bending and tensile strength, as well as on technological parameters like
permeability, abrasion resistance and apparent density. The research revealed a significant positive effect of adding water to wet surfaces
of high-silica base grains on mechanical properties and quality of moulding sands hardened by physical methods, in particular by
microwave heating
The paper presents results of initial research on the possibility of applying microwave radiation in an innovative process of making casting
moulds from silica sand, where gypsum CaSO4∙2H2O was acting as a binding material. In the research were compared strengths and
technological properties of moulding mixture subjected to: natural bonding process at ambient temperature or natural curing with
additional microwave drying or heating with the use of microwaves immediately after samples were formed. Used in the research
moulding sands, in which dry constituents i.e. sand matrix and gypsum were mixed in the ratio: 89/11. On the basis of the results of
strength tests which were obtained by various curing methods, beneficial effect of using microwaves at 2.45 GHz for drying up was
observed after 1, 2 and 5 hours since moisture sandmix was formed. Applying the microwaves for hardening just after forming the samples
guarantees satisfactory results in the obtained mechanical parameters. In addition, it has been noted that, from a technological and
economic point of view, drying the silica sand with gypsum binder in microwave field can be an alternative to traditional molding sand
technologies.
This paper presents initial findings from research into the possibility of using gypsum binders in quartz moulding sand that could be used in the production of casting moulds and cores. For the purposes of the research two commercial types of gypsum were used as binders: building gypsum and gypsum putty. Dry components of moulding sand i.e. medium quartz sand and gypsum were mixed in proportion of 89/11 parts by weight. In order to achieve bonding properties for the binders, 5 parts by weight of water was added to the mixture of dry components. After 24 hours of adding water and mixing all the components, the moulding sand, naturally hardened, was subjected to high temperature. The moulding sand thus produced, i.e. with cheap and environmentally-friendly gypsum binders, was eventually analysed after heating (at temperatures of 300oC, 650oC and 950oC) and cooling in order to determine changes in the following parameters: LOI – loss on ignition, chemical composition and pH. Moreover, investigated were bonding bridges, before and after the moulding sand was roasted. The research results revealed differences in the structure of bonding bridges and the occurrence of automatic adhesive destruction for both types of gypsum binders. For two types of moulding sands under the investigation of the LOI exceeded 2.59wt.% (with building gypsum) or 2.84wt.% (with putty gypsum) and pH increased to ca. 12 as a result of increasing roasting temperature from 300oC to 650oC. Next, roasting at 950oC decrease value of LOI in both types of moulding sands. Moulding sand with builoding gypsum roasted at 950oC revealed a return to the value of pH parameter measured prior to annealing.
The paper presents the preliminary results of research on determining the possibilities of using available on the market commercial gypsum kinds as a binder for foundry moulding and core sandmixes. Construction gypsum and plaster gypsum, finishing coat and jewelry casting gypsum were tested. Elemental composition of gypsum kinds were carried out using a scanning electron microscope (SEM) with EDS/EDX probe, their crystal structure and phase composition was determined by analyzing the results of X-ray diffraction measurements (XRD) and thermogravimetric studies (TG-DTA). Evaluation of the mechanical properties of selected materials was carried out at the tensile strength test of the dog-bone samples after initial hardening of gypsum mortar at 25 °C for 5 h and drying at 110 °C for 24 hours. The impact of the properties of the used commercial gypsum kinds on the possibility of their use as a valuable binders in the manufacture of the foundry sandmixes for moulds and cores was evaluated. Construction gypsum and finishing coat have the highest tensile strength. Plaster gypsum and finishing coat have the longest setting time. In all tested types of gypsum, the initial water loss during heating occurs at a temperature of about 200 °C. The lowest valuable properties as a binder for sand moulding mixtures has jewelry casting gypsum mass.
The paper presents the results of preliminary research on the application of olivine moulding sands with hydrated sodium silicate containing 1.5 % wt. of binder to perform ecological casting cores in hot-box technology using a semi-automatic core shooter. The following parameters were used in the process of core shooting: initial shot pressure of 6 bar, shot time 3 s, the temperature of the corebox: 200, 250 and 300 °C and the core curing time: 30, 60, 90, 120 and 150 s. The matrix of the moulding mixture was olivine sand, and the binder of the sandmix was commercial, unmodified hydrated sodium silicate with molar module SiO2/Na2O of 2.5. In one shot of the automatic core-shooter were formed three longitudinal specimens (cores) with a dimensions 22.2×22.2×180 mm. The samples obtained in this way were subjected to the assessment of the influence of the shooting parameters, i.e. shooting time, temperature and curing time in core-box, using the following criteria: core box fill rate, mechanical strength to bending Rg U, apparent density, compaction degree and susceptibility to friability of sand grains after hardening. The results of trials on the use of olivine moulding sands with hydrated sodium silicate (olivine SSBS) in the process of core shooting made it possible to determine the conditions for further research on the improvement of inorganic hot-box process technology aimed at: reduction of the heating temperature and the curing time. It was found that correlation between the parameters of the shooting process and the bending strength of olivine moulding sands with sodium silicate is observed.
This paper outlines issues associated with gas-shielded braze welding of CU-ETP copper with austenitic steel X5CrNi18-10 (1.4301) using a consumable electrode. The possibilities for producing joints of this type using innovative low-energy welding methods are discussed. The paper provides an overview of the results of metallographic and mechanical (static shear test, microhardness) tests for braze welded joints made on an automated station using the Cold Metal Transfer (CMT) method. Significant differences in the structure and mechanical properties are indicated, resulting from the joint configuration and the type of shielding gas (argon, helium).
In the paper, a research on effects of baking temperature on chromite sand base of moulding sands bonded with sodium silicate is
presented. Pure chromite sand and its chromite-based moulding sand prepared with use of sodium silicate were subjected to heating within
100 to 1200 °C. After cooling-down, changes of base grains under thermal action were determined. Chromite moulding sand was prepared
with use of 0.5 wt% of domestic made, unmodified sodium silicate (water-glass) grade 145. After baking at elevated temperatures, creation
of rough layer was observed on grain surfaces, of both pure chromite sand and that used as base of a moulding sand. Changes of sand
grains were evaluated by scanning microscopy and EDS analyses. It was found that changes on grain surfaces are of laminar nature. The
observed layer is composed of iron oxide (II) that is one of main structural components of chromite sand. In order to identify changes in
internal structure of chromite sand grains, polished sections were prepared of moulding sand hardened with microwaves and baked at
elevated temperatures. Microscopic observations revealed changes in grains structure in form of characteristically crystallised acicular
particles with limited magnesium content, intersecting at various angles. EDS analysis showed that these particles are composed mostly of
chromium oxide (III) and iron oxide (II). The temperature above that the a.m. changes are observed in both chromite-based moulding sand
and in pure chromite sand. The observed phenomena were linked with hardness values and mass of this sand.
In the paper presented are results of a research on influence of electrical and physico-chemical properties of materials being parts of
multicomponent and multimaterial systems used in foundry practice on efficiency and effectiveness of microwave heating. Effectiveness
of the process was evaluated on the grounds of analysis of interaction between selected parameters of permittivity and loss factor, as well
as collective index of energy absorbed, reflected and transmitted by these materials. In the examinations used was a stand of waveguide
resonance cavity for determining electrical properties and a stand of microwave slot line for determining balance of microwave power
emitted into selected materials. The examinations have brought closer the possibility of forecasting the behaviour of multimaterial systems
like e.g. model, moulding sand or moulding box in microwave field on the grounds of various electrical and physico-chemical properties.
On the grounds of analysis of the results, possible was selecting a group of materials designed for building foundry instrumentation to be
effectively used in electromagnetic field.