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The work presents the test result of the influence of cooling rate on the microstructure of AZ91 alloy, Vickers micro-hardness and Brinell hardness. Studies cooling and crystallization of AZ91 alloy was cast into the ceramic shells pre-heated to 180 ° C and then air-cooled at ambient temperature or intensively super cooled in the liquid coolant. The TDA method was applied to record and characterize the thermal effect resulting from the phase transformations occurring during the crystallization of AZ91 alloy. The kinetics and dynamics of the thermal processes of crystallization of AZ91 alloy in the ceramic shells were determined. Metallographic tests were performed with the use of an optical microscope. A comparison of these test results with the thermal effect recorded by way of the TDA method was made. Influence of cooling rate of AZ91 on HV0, 01 micro-hardness and Brinell hardness alloy was examined.
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The performed examinations concerning the process of filling the plaster ceramic moulds with aluminium alloys allowed to assess the influence of various methods of introducing the metal into the mould cavity on the macro- and microstructure of the obtained experimental castings. The comparison was performed for castings with graded wall thickness made either of EN AC-44000 alloy or of EN AC-46000 alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the Vacumetal technology), or by counter-gravity casting. It was found that the silicon crystals grow in size with an increase in wall thickness due to the slower cooling and solidification of castings.
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The work deals with the influence of change in the filling conditions of the ceramic moulds with plaster binder on the presence of gaseous porosity and the microstructure of the achieved test castings with graded wall thickness. Castings made of EN AC-44000 alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the Vacumetal technology), or by counter-gravity casting were compared. The results of examinations concerning the density of the produced castings indicate that no significant change in porosity was found. The increased size of silicon crystals was found for the increased wall thicknesses due to the slower cooling and solidification of castings.
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The paper presents the use of rapid prototyping technology of three dimensional printing (3DP) to make a prototype shell casting mold. In the first step, for identification purposes, a mold was prepared to enable different alloys to be cast. All molds being cast were designed in a universal CAD environment and printed with the zp151 composite material (Calcium sulfate hemihydrate) with a zb63 binder (2- pyrrolidone). It is designated to be used to prepare colourful models presenting prototypes or casting models and molds. The usefulness of 3DP technology for use with copper alloys, aluminum and zinc was analyzed. The strength of the mold during casting was assumed as a characteristic comparative feature in the material resistance to high temperature, the quality of the resulting casting and its surface roughness. Casting tests were carried out in vacuum – pressure casting. The casting programs applied, significantly increased the quality of castings and enabled precise mold submergence. Significant improvement was noted in the quality compared to the same castings obtained by gravity casting.
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The study presents the results of the investigations of the effect of Cu, Ni, Cr, V, Mo and W alloy additions on the microstructure and mechanical properties of the AlSi7Mg0.3 alloy. The examinations were performed within a project the aim of which is to elaborate an experimental and industrial technology of producing elements of machines and devices complex in their construction, made of aluminium alloys by the method of precision investment casting. It was demonstrated that a proper combination of alloy additions causes the crystallization of complex intermetallic phases in the silumin, shortens the SDAS and improves the strength properties: Rm, Rp0.2,HB hardness. Elevating these properties reduces At, which, in consequence, lowers the quality index Q of the alloy of the obtained casts. Experimental casts were made in ceramic moulds preliminarily heated to 160 °C, into which the AlSi7Mg0.3 alloy with the additions was cast, followed by its cooling at ambient temperature. With the purpose of increasing the value of the quality index Q, it is recommended that the process of alloy cooling in the ceramic mould be intensified and/or a thermal treatment of the casts be performed (ageing)(T6).
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The study discusses the issues connected with the production of thin-walled ceramic slurry in the replicast cs technology. In the ceramic mould production process, a special role is played by the liquid ceramic slurry used to produce the first layer of the mould. The study examines selected technological properties of liquid ceramic slurries used to produce moulds in the replicas cs technology. The ceramic slurries for the tests were prepared based on the binders Ludox Px30 and Sizol 030, enriched with Refracourse flour. The wettability of the pattern's surface by the liquid ceramic slurry and the dependence of the apparent viscosity on the ceramic flour content in the mixture were determined. The wettability of the pattern surface by the liquid ceramic slurry was determined based on the measurement of the wetting angle. The angle was determined by means of an analysis of the computer image obtained with the use of a CDC camera.
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The results of estimation of home scrap addition in charge influence on durability and wear of casting instrumentation life in the highpressure casting technology using the hot chamber machine of alloy of AZ91 are presented. The wear of the following elements of the casting instrumentation so-called "casting set" as: syphon, plunger, sliding-rings, nozzle and injection moulding nozzle was estimated. A wear was estimated quantitative by registering the number of mould injections for different charges to the moment of element damage supervision. A damage had to be at such level that liquidated an element from further exploitation and necessary was an exchange on new or regeneration. In a final result allowed it the detailed determination of durability of the applied rigging elements in dependence on the type of the applied type of melt. It is noticed, that together with the increase of home-scrap participation in the charge wear of pressure machine instrumentation elements increases.
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The work is a continuation of research on the use water mist cooling in order to increase efficiency of die-casting aluminum alloys. The paper presents results of research and analysis process, spraying water and generated a stream of water mist, the effect of the type of nozzle, the nozzle size and shape of the emitting of the water mist on the wall surface of casting die on the microstructure and geometry of water mist stream and cooling efficiency. Tests were used to perform high-speed camera to record video in the visible and infrared camera. Results were used to develop a computerized image analysis and statistical analysis. The study showed that there are statistical relationships between water and air flow and geometry of the nozzle and nozzle emitting a stream of microstructure parameters of water mist and heat the incoming stream. These relationships are described mathematical models that allow you to control the generating of adequate stream of water mist and a further consequence, the cooling efficiency of casting die.
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The paper presents the results of studies on the development of correlation of solidification parameters and chemical composition of nickel superalloy IN-713C, which is used i.a. on aircraft engine turbine blades. Previous test results indicate significant differences in solidification parameters of the alloy, especially the temperatures Tliq and Tsol for each batch of ingots supplied by the manufacturer. Knowledge of such a relationship has important practical significance, because of the ability to asses and correct the temperatures of casting and heat treatment of casts on the basis of chemical composition. Using the statistical analysis it was found that the temperature of the solidification beginning Tliq is mostly influenced by the addition of carbon (similar to iron alloys). The additions of Al and Nb have smaller but still significant impact. Other alloying components do not have significant effect on Tliq. The temperature Teut is mostly affected by Ni, Ti and Nb. The temperature Tsol is not in any direct correlation with the chemical composition, which is consistent with previous research. The temperature Tsol depends primarily on the presence of non-metallic inclusions present in feed materials and introduced during the melting and casting processes.
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The paper presents the results of research on the determination of the effect of pouring temperature on the macrostructure of the castings subjected to complex (surface and volume) modification and double filtration. Tested castings were made of post-production scrap (gating system parts) of IN-713C superalloy. Tests included the evaluation of the number of grains per 1 mm2 , mean grain surface area, shape factor and tensile strength. Casting temperature below 1470 °C positively influenced the modification effect. The grains were finer and the mechanical properties increased, especially for castings with thicker walls. On the other hand, manufacture of thin walled castings of high quality require pouring temperature above 1480 °C.
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The aging granulate is to activate the blowing agent during the manufacturing process to granulate models can re-expand and shape the model of well-sintered granules, smooth surface and a suitable mechanical strength. The article presents the results of studies which aim was to determine the optimum time for aging pre-foamed granules for pre-selected raw materials. The testing samples were shaped in an autoclave, with constant parameters sintering time and temperature. Samples were made at 30 minute intervals. Models have been subjected to flexural strength and hardness.
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The work is a continuation of research on the use water mist cooling in order to increase efficiency of die-casting aluminum alloys using multipoint water mist cooling system. The paper presents results of investigation of crystallization process and microstructure of synthetic hypereutectic AlSi20 alloy. Casts were made in permanent mold cooled with water mist stream. The study was conducted for unmodified AlSi20 alloy and modified with phosphorus, titanium and boron on the research station allowing sequential multipoint cooling using a dedicated program of computer control. The study demonstrated that the use of mold cooled with water mist stream allows the formation of the microstructure of hypereutectic silumins. A wide range of solidification temperature of hypereutectic silumins increases the potential impact of changes in the cooling rate on a size, a number and a morphology of preeutectic silicon and eutectic α+β (Al+Si).
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Development of salt cores prepared by high-pressure squeezing and shooting with inorganic binders has shown a high potential of the given technology even for high-pressure casting of castings. Strength, surface quality of achieved castings, and solubility in water become a decisive criterion. The shape and quality of grain surface particularly of NaCl – cooking salts that can be well applied without anticaking additives has shown to be an important criterion. Thus the salt cores technology can cover increasingly growing demands for casting complexity especially for the automobile industry.
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The herein paper contains the results of investigations on a new type of cellulose blend used for the manufacture of profiles applied in the process of making gating systems in the foundry industry. A standard cellulose profile was subjected to an experiment. During the experiment the profile was filled with a liquid cast iron and at the same time the temperatures of the liquid metal crystallizing inside the profile were measured as well as the temperature of the outer layer of the profile was controlled. Further, the microstructure of the cast iron, which crystallized out inside the cellulose profile, was analysed and the cellulose, thermally degraded after the experiment, was verified with the use of the chemical analysis method. Moreover, a quality analysis of the original as well as the degraded cellulose profile was run with the use of the FTIR infrared spectroscopy. The presented results revealed that the cellulose blend is aluminium silicate enriched and contains organic binder additives. The cast iron, which crystallized out, tended to have an equilibrium pearlitic structure with the release of graphite and carbides. The generation of disequilibrium ausferrite phases was also observed in the structure.
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The work is a continuation of research on the use of water mist cooling in order to increase efficiency of the die-casting process for aluminum alloys. The paper describes the multipoint sequential cooling system of the casting die and its computer control and monitoring. It also includes results of the tests and analysis of cooling methods during making of the casting. These methods differ from each other in the sequence of casting die cooling and cause effective changes in microstructure and mechanical properties of castings made of AlSi11 alloy. The study demonstrated that the use of multipoint sequential cooling with water mist affects the microstructure refinement and reduces the segregation in the cast as well as more than by 20% increases the mechanical properties of castings in the rough state. The study also demonstrates that the sequential cooling of casting die accelerates the cooling of the casting and shortens die-casting cycle.
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The work is a continuation of research on the use of water mist cooling in order to increase efficiency of die-casting aluminum alloys using multipoint water mist cooling system. The paper presents results of investigation on crystallization process and microstructure of synthetic hypereutectic AlSi20 alloy. Casts were made in permanent mold cooled a with water mist stream. The study was conducted for unmodified AlSi20 alloy and a modified one with phosphorus, titanium and boron on the research station allowing sequential multipoint cooling using a dedicated program of computer control. The study demonstrated that the use of mold cooled with water mist stream and solution heat treatment allows in wide range for the formation of the microstructure of hypereutectic silumins. It leads to the growth of microstructure refinement and spheroidizing of phases in the casting.
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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.
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The development of economy and industry introducing new technologies and materials often means the increased threat of occurrence of factors harmful to humans and environment. Workers employed in foundries as mould pourers are the group of high professional risk. Foundry moulding sands when poured with liquid metal are a source of the emission of harmful, toxic and carcinogenic (benzene, PAHs) compounds. The paper presents the results of studies on the concentration of chemical compounds emitted in the process of casting aluminium alloy and brass using moulding sands with the new inorganic binders. The specific values of the exposure indices were compared with the limit values. This enabled an assessment of the impact of moulding sands on work environment. The obtained results were compared with the values of contaminants emitted when pouring foundry moulds made from furan sands and bentonite sands with an addition of coal dust. Studies were carried out under the project POIG.01.01.02-00-015/09 "Advanced materials and technologies."
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The work presents the results of the investigations of the effect of inhibitors coated on the internal walls of a ceramic mould on the quality of the obtained casts made of the AM60 alloy containing additions of chromium and vanadium. In order to reduce the reactivity of magnesium alloy cast by the technology of investment casting with the material of the mould and the ambient atmosphere, solid inhibitors were applied in the form of a mixture of KBF4 and H3BO3 after the stage of mould baking and before the mould’s being filled with the liquid alloy. For the purpose of examining the effect of the inhibitors on the surface quality of the obtained casts, profilometric tests were performed and the basic parameters describing the surface roughness, Ra, Rz and Rm, were determined.
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In current casting technology of cored, thin walled castings, the modifying coating is applied on the surface of wax pattern and, after the removal of the wax, is transferred to inner mould surface. This way the modification leading to grain refinement occur on the surface of the casting. In thin walled castings the modification effect can also be seen on the other (external) side of the casting. Proper reproduction of details in thin walled castings require high pouring temperature which intensify the chemical reactions on the mould – molten metal interface. This may lead to degradation of the surface of the castings. The core modification process is thought to circumvent this problem. The modifying coating is applied to the surface of the core. The degradation of internal surface of the casting is less relevant. The most important factor in this technology is “trough” modification – obtaining fine grained structure on the surface opposite to the surface reproduced by the core.
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The work is a continuation of research concerning the influence of intensive cooling of permanent mold in order to increase the casting efficiency of aluminium alloys using the multipoint water mist cooling system. The paper presents results of investigation of crystallization process and microstructure of synthetic hypereutectic alloys: AlSi15 and AlSi19. Casts were made in permanent mold cooled with water mist stream. The study was conducted for unmodified silumins on the research station allowing the cooling of the special permanent probe using a program of computer control. Furthermore the study used a thermal imaging camera to analyze the solidification process of hypereutectic silumins. The study demonstrated that the use of mold cooled with water mist stream allows in wide range the formation of the microstructure of hypereutectic silumins. It leads to higher homogeneity of microstructure and refinement of crystallizing phases and also it increases subsequently the mechanical properties of casting.
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This article presents the results of studies in the hypoeutectic silumin destined for pressure die casting with the simultaneous addition of chromium and tungsten. The study involved the derivative and thermal analysis of the crystallization process, metallographic analysis and mechanical properties testing. Silumin 226 grade was destined for studies. It is a typical silumin to pressure die casting. AlCr15 and AlW8 preliminary alloys were added to silumin. Its quantity allowed to obtain 0.1, 0.2, 0.3 and 0.4% of Cr and W in the tested alloy. Studies of the crystallization process as well as the microstructure of the silumin poured into DTA sampler allowed to state the presence of additional phase containing 0.2% or more Cr and W. It has not occurred in silumin without the addition of above mentioned elements. It is probably the intermetallic phase containing Cr and W. DTA studies have shown this phase crystallizes at a higher temperature range than α (Al) solid solution. In the microstructure of each pressure die casting containing Cr and W the new phases formed. Mechanical properties tests have shown Cr and W additives in silumin in an appropriate amount may increase its tensile strength Rm (about 11%), the yield strength Rp0.2 (about 21%) and to a small extent elongation A.
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The paper analyses specific defects of castings produced by semi-solid casting process, especially rheocasting method SEED, which uses mechanical swirling for reaching proper structure in semisolid state with high content of solid fraction. Heat treated alloy AlSi7Mg0.3 was applied for producing an Engine Bracket casting part. For observing structure, metallographic observation by light and SEM microscopy was used. To analyse the process, software ProCAST was used to simulate the movements in shot chamber and filling of the mold.
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The paper presents the microstructure and selected properties of ausferritic nodular cast iron annealed at the temperature 520 and 550°C. This choice was dictated by the temperatures used in the practice of nitriding. Nodular graphite in cast iron was obtained with use of Inmold process. Cast iron containing molybdenum and copper ensuring obtaining an ausferrite in the cast iron matrix without the use of heat treatment of castings was tested. The effect of annealing temperature on the microstructure and the kind of fracture of the ausferritic nodular cast iron was presented. The effect of an annealing temperature on hardness, impact strength and the microhardness of ausferritic nodular cast iron matrix was shown too. The lamellar structure of phases in the cast iron matrix after annealing has been ascertained. There has been an increase in hardness of an annealed cast iron and microhardness of its matrix. The reduction in the impact strength of the cast iron annealed at 520 and 550°C was approximately 10-30%. Both an increase in the hardness of cast iron as well as an decrease in its impact strength is probably due to the separation of secondary carbides during the heat treatment.
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In highly developed countries, a significant progress in the use of alternative and clean energy sources has recently been observed. The European Union has implemented a programme to build wind turbines. It is estimated that in the coming years, thanks to the support in tax and credit, the global energy will develop very intensively. Many components of the wind turbines are castings. The basic material used for these castings is ductile iron, which in this particular case must meet high requirements imposed by the operating conditions of wind turbines. Anticipating an increase in customer demand for this type of castings, Krakodlew SA has decided to modernize its foundry using the ability to obtain external financing. The ductile iron manufacturing technology is now being developed and adapted to the specific conditions of the foundry plant, including the melting process yielding cast material with the required chemical composition, the technology of moulding, and the conditions for possible secondary metallurgy, spheroidizing treatment and graphitizing inoculation. The fulfilment of the imposed conditions for the casting production demands the use of advanced casting technologies introduced to the manufacturing process. The development of technology to launch the production of ductile iron castings for the wind power industry was supported by The National Centre for Research and Development (NCBiR). This article presents part of research on the binding kinetics of furan resin sands and choice of their composition for moulds and cores to make heavy castings used as components of equipment for the wind power industry.
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