Describes how to obtain a soluble sodium silicate with a density of 1.40 g/cm3, 1.45 g/cm3, 1.50 g/cm3, and silica module M = 2.1 obtained from the silica- sodium glass with module M = 3.3 and M = 2.1. Residual (final) strength of molding samples made with these binders, were determined at temperatures corresponding to the characteristic temperatures of phase and temperature transitions of silica gel. Indicated the type of soluble sodium silicate capable of obtain the smallest value of the final strength of molding sand in the specified range of temperatures.

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, 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.

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 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 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.

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.

The aim of this study is to demonstrate the possibility of using moulds made from the environmentally friendly sands with hydrated sodium silicate in modified ablation casting. The ablation casting technology is primarily intended for castings with diversified wall thickness and complex shapes made in sand moulds. The article presents the effect of binder content and hardening time on the bending strength Rg u of moulding sands with binders based on hydrated sodium silicate hardened by microwave technology. The aim of the research was to develop an optimal sand composition that would provide the strength necessary to make a mould capable of withstanding the modified ablation casting process. At the same time, the sand composition should guarantee the susceptibility of the mould to the destructive action of the ablation medium, which in this case is water. Tests have shown that microwave hardening provides satisfactory moulds’ strength properties even at a low binder content in the sand mixture.

The presented in the paper investigations were aimed at the determination of the reclaimed material (obtained in the dry mechanical

reclamation process) addition influence on properties of moulding sands with hydrated sodium silicate modified by colloidal suspension

of zinc oxide nanoparticles in propanol. Nanoparticles originated from the thermal decomposition of alkaline zinc carbonate, were used.

The results of the reclamation of the spent moulding sand with hydrated sodium silicate performed in the AT-2 testing reclaimer are

presented in the paper. Both, spent sands from the Floster S technology and from the technology with the modified water-glass were

subjected to the reclamation processes. The following determinations of the reclaimed material were performed: pH reaction, acid demand,

ignition loss and Na2O content. The obtained reclaim was used as a matrix component of moulding sands with water-glass in the Floster S

technology, in which it constituted 60% and 50% of the sand matrix. The strength properties of the prepared moulding sands were

determined (bending strength Rg

u

, tensile strength Rm

u

) after samples storing times: 1h, 2h, 4h and 24 hours.

The ablation casting technology consists in pouring castings in single-use moulds made from the mixture of sand and watersoluble binder. After pouring the mould with liquid metal, while the casting is still solidifying, the mould destruction (washing out, erosion) takes place using a stream of cooling medium, which in this case is water. The following paper focuses on the selection of moulding sands with hydrated sodium silicate technologies for moulds devoted to the ablation casting of aluminum alloys. It has been proposed to use different types of moulding sands with a water-soluble binder, which is hydrated sodium silicate. The authors showed that the best kind of moulding sands for moulds for Al alloy casting will be moulding sands hardened with physical factors – through dehydration. The use of microwave hardened moulding sands and moulding sands made in hot-box technology has been proposed. The tests were carried out on moulding sands with different types of modified binder and various inorganic additives. The paper compares viscosity of different binders used in the research and thermal degradation of moulding sands with tested binders. The paper analyzes the influence of hardening time periods on bending strength of moulding sands with hydrated sodium silicate prepared in hot-box technology. The analysis of literature data and own research have shown that molding sand with hydrated sodium silicate hardened by dehydration is characterized by sufficient strength properties for the ablation foundry of Al alloys.

The ablation casting technology consists in pouring castings in single-use moulds made from the mixture of sand and water-soluble binder. After pouring the mould with liquid metal the mould is destructed (washed out) using a stream of cooling medium, which in this case is water. The process takes place while the casting is still solidifying.

The following paper focuses on testing the influence of the modified ablation casting of aluminum alloy on casts properties produced in moulds with hydrated sodium silicate binder. The authors showed that the best kind of moulding sands for Al alloy casting will be those hardened with physical factors – through dehydration. The analysis of literature data and own research have shown that the moulding sand with hydrated sodium silicate hardened by dehydration is characterized by sufficient strength properties for the modified ablation casting of Al alloys. In the paper the use of microwave hardened moulding sands has been proposed.

The moulds were prepared in the matrix specially designed for this technology. Two castings from the AlSi7Mg alloy were made; one by traditional gravity casting and the other by gravity casting using ablation.

The conducted casts tests showed that the casting made in modified ablation casting technology characterizes by higher mechanical properties than the casting made in traditional casting technology. In both experimental castings the directional solidification was observed, however in casting made by ablation casting, dimensions of dendrites in the structure at appropriate levels were smaller.