In this work, the influence of microwave drying parameters such as irradiation time and microwave power level on the properties of synthetic moulding sands is presented. Determination of compressive strength Rc s, shear strength Rt s and permeability Ps of synthetic moulding sands with the addition of two different bentonites, after drying process with variable microwave parameters were made. The research works were carried out using the microwave oven with regulated power range of the electromagnetic field. From the results obtained, the significant influence of both drying time and microwave power level on the selected properties of moulding sands was observed. In comparison to the conventional drying method, microwave drying allows to obtain higher compressive strength of the synthetic moulding sand. The influence of application microwave irradiation on permeability was not observed. Higher strength characteristics and shorter drying time are major advantages of application of the electromagnetic irradiation for drying of the synthetic moulding sand with regard to conventional drying method.

Within the research, selected multilayer technological systems created as combinations of water-glass containing moulding sand with

foundry tooling, were characterised on the grounds of their electrical properties. By measuring resonance frequency and quality factor of a

waveguide resonance cavity, real component of permittivity εr′ and loss tangent tgδ were determined for multilayer foundry systems with

various qualitative and quantitative compositions. It was demonstrated that combination of a sandmix and foundry tooling with known

dielectric properties results in a system with different physico-chemical properties, whose relation to the parameters of individual

components of the system is undefined at this research stage. On the grounds of measurement results, theoretical value of microwave

heating power, dissipated in unit volume of the selected multilayer foundry system, was determined. Knowledge of theoretical heating

power and evaluation of physical, chemical and structural changes occurring in moulding sands exposed to microwaves in such a

technological system makes a ground for empirical modelling of the process of microwave heating of foundry moulds and cores.

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.

The paper presents the results of basic research on the influence of the properties of sand grains on electrical properties of water glass

moulding sands. It shows electrical properties of the main component – sand grains, crucial to the kinetics of moulding sands heating, such

as permittivity εr and loss factor tgδ. Measurements were carried out with the use of the perturbation method for silica, chromite and

olivine sands of different mineral, chemical composition and particle size distribution, as well as for moulding sands with water glass

grade 145. Analysis of the results of measurements of electrical properties shows that all moulding sands are characterized by a similar

permittivity εr and loss factor tgδ. It was found that the electrical properties and the quantity and quality of other components may have

a decisive influence on the effectiveness and efficiency of the microwave heating of moulding sands with sand grains. In determining the

ability to efficiently absorb the microwave radiation for mixtures which moulding sands are, the impact of all components influencing their

individual technological parameters should be taken into account.

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.

Presented are results of a preliminary research on determining a possibility to use microwave radiation for drying casting protective

coatings applied on patterns used in the lost foam technology. Taken were measurements of permittivity εr and loss factor tgδ at 2.45 GHz,

as well as attempts were made of microwave drying of a protective coating based on aluminium silicates, applied on shapes of foamed

polystyrene and rigid polymeric foam. Time and results of microwave drying were compared with the results obtained by drying at 50 °C

by the traditional method commonly used for removing water from protective coatings. Analysis of the obtained drying kinetics curves

demonstrated that selection of proper operation parameters of microwave equipment permits the drying time to be significantly shortened.

Depending on kind of the pattern material, drying process of a protective coating runs in a different way, resulting in obtaining different

quality of the dried coating.

The research paper presents the results of testing the strength and technological properties of molding sand with gypsum binder, the bonding process proceeded: naturally or conventionally. The tests included mass containing (parts by weight): 78 pbw. Grudzeń-Las quartz sand, 22 pbw. plaster gypsum "Dolina Nidy” and 9 pbw. water. Measurements of compressive strength, shear, tensile and bending as well as permeability and looseness were carried out on standard cylindrical samples kept in the air for 1 - 96 hours or dried at 110 oC for 1 - 8 hours. The results of the analysis were analyzed in connection with the mass structure and construction binding bridges warp grains observed with a scanning microscope (SEM). The influence of drying intensity on the bonding process and related mass properties has been demonstrated, especially from the point of view of the possibility of selection and / or intensification of a specific curing method for use in the production of gypsum binger molds and cores.

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.

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.