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The paper presents the initial results of investigation concerning the abrasion resistance of cast iron with nodular, vermicular, or flake graphite. The nodular and vermicular cast iron specimens were cut out of test coupons of the IIb type with the wall thickness equal to 25 mm, while the specimens made of grey cast iron containing flake graphite were cut out either of special casts with 20 mm thick walls or of the original brake disk. The abrasion tests were carried out by means of the T-01M tribological unit working in the pin-on-disk configuration. The counterface specimens (i.e. the disks) were made of the JT6500 brand name friction material. Each specimen was abraded over a distance of 4000 m. The mass losses, both of the specimens and of the counterface disks, were determined by weighting. It was found that the least wear among the examined materials was exhibited by the nodular cast iron. In turn, the smallest abrasion resistance was found in vermicular cast iron and in cast iron containing flake graphite coming from the brake disk. However, while the three types of specimens (those taken from the nodular cast iron and from grey cast iron coming either from the special casts or from the brake disk) have almost purely pearlitic matrix (P95/Fe05), the vermicular cast iron matrix was composed of pearlite and ferrite occurring in the amounts of about 50% each (P50/Fe50). Additionally, it was found that the highest temperature at the cast iron/counterface disk contact point was reached during the tests held for the nodular cast iron, while the lowest one occurred for the case of specially cast grey iron.
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Results of a research on influence of chromium, molybdenum and aluminium on structure and selected mechanical properties of Ni-Mn-Cu cast iron in the as-cast and heat-treated conditions are presented. All raw castings showed austenitic matrix with relatively low hardness, making the material machinable. Additions of chromium and molybdenum resulted in higher inclination to hard spots. However, a small addition of aluminium slightly limited this tendency. Heat treatment consisting in soaking the castings at 500 °C for 4 h resulted in partial transformation of austenite to acicular, carbon-supersaturated ferrite, similar to the bainitic ferrite. A degree of this transformation depended not only on the nickel equivalent value (its lower value resulted in higher transformation degree), but also on concentrations of Cr and Mo (transformation degree increased with increasing total concentration of both elements). The castings with the highest hard spots degree showed the highest hardness, while hardness increase, caused by heat treatment, was the largest in the castings with the highest austenite transformation degree. Addition of Cr and Mo resulted in lower thermodynamic stability of austenite, so it appeared a favourable solution. For this reason, the castings containing the highest total amount of Cr and Mo with an addition of 0.4% Al (to reduce hard spots tendency) showed the highest tensile strength.
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Ablation casting is a technological process in which the increased cooling rate causes microstructure refinement, resulting in improved mechanical properties of the final product. This technology is particularly suitable for the manufacture of castings with intricate shapes and thin walls. Currently, the ablation casting process is not used in the Polish industry. This article presents the results of strength tests carried out on moulding sands based on hydrated sodium silicate hardened in the Floster S technology, intended for ablation casting of the AlSi7Mg (AK7) aluminium alloy. When testing the bending and tensile strengths of sands, parameters such as binder and hardener content were taken into account. The sand mixtures were tested after 24h hardening at room temperature. The next stage of the study describes the course of the ablation casting process, starting with the manufacture of foundry mould from the selected moulding mixture and ending in tests carried out on the ready casting to check the surface quality, structure and mechanical properties. The results were compared with the parallel results obtained on a casting gravity poured into the sand mould and solidifying in a traditional way at ambient temperature.
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Early Buddhism was a predominantly spiritual movement which should ideally culminate in Enlightenment. Yet, it was embedded in the specific social environment of ancient India which included a hereditary caste system. Using the Buddhist Pāli texts and non-Buddhist literature from up until the last centuries BCE the article examines the four main hereditary categories (vaṇṇa, jāti, gotta, and kula) and how Early Buddhism related to them. We conclude that the Buddha and Early Buddhism did not oppose but rather confirmed the hereditary systems in society as well as its designations within the monastic community. The Buddha hereby followed the customs of earlier ascetic movements and imposed no specific rules on the monastics to eradicate their former social identity.
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Investment casting combined with the additive manufacturing technology enables production of the thin-walled elements, that are geometrically complex, precise and can be easy commercialized. This paper presents design of aluminium alloy honeycombs, which are characterized with light structure, internal parallel oriented channels and suitable stiffness. Based on 3D printed pattern the mould was prepared from standard ceramic material subjected subsequently to appropriate heat treatment. Into created mould cavity with intricate and susceptible structure molten AC 44200 aluminium alloy was poured under low pressure. Properly designed gating system and selected process parameters enabled to limit the shrinkage voids, porosities and misruns. Compression examination performed in two directions showed different mechanisms of cell deformation. Characteristic plateau region of stress-strain curves allowed to determine absorbed energy per unit volume, which was 485 or 402 J/mm3 depending on load direction. Elaborated technology will be applied for the production of honeycomb based elements designated for energy absorption capability.
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The mathematical model and numerical simulations of the solidification of a cylindrical shaped casting, which take into account the process of filling the mould cavity by liquid metal and feeding the casting through the riser during its solidification, are presented in the paper. Mutual dependence of thermal and flow phenomena were taken into account because have an essential influence on solidification process. The effect of the riser shape on the effectiveness of feeding of the solidifying casting was determined. In order to obtain the casting without shrinkage defects, an appropriate selection of riser shape was made, which is important for foundry practice. Numerical calculations of the solidification process of system consisting of the casting and the conical or cylindrical riser were carried out. The velocity fields have been obtained from the solution of momentum equations and continuity equation, while temperature fields from solving the equation of heat conductivity containing the convection term. Changes in thermo-physical parameters as a function of temperature were considered. The finite element method (FEM) was used to solve the problem.
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This article discusses issues related to continuous casting of brass. The tested material was CuZn39Pb2 brass with the use of continuous casting and different parameters of the process. The position consists of a melting furnace with a graphite refining pot of about 4000 cm3 chuting capacity, a graphite crystallizer of 9,5 mm nominal diameter, a primary and secondary cooling system and an extracting system as well. The analysis was carried out in terms of technological parameters of the process and type of charge. Highlighted: feedrate ingot, number of stops, and technological temperatures. The surface quality of the obtained ingots and the structure were analyzed. The most favorable conditions were indicated and technological recommendations indicated. They have been distinguished for ingots for plasticity and other technologies. Favorable casting conditions are low feed and low temperature. Due to the presence of impurities coming from the charge it is disadvantageous to have Ni greater than 0.053% by mass, and Fe more than 0.075% by mass. It is recommended to maintain a high zinc content in the melt which is associated with non-overheating of the metal during casting and earlier melting.
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Metallic bearing alloys have different types, most of which are tin (Babbitt) or bronze based. Bronze bearings are used at heavy duty conditions. The goal of this research is an investigation on the effect of cooling rate and pouring temperature (two important factors in casting production) on the Brinell hardness and pin-on-disc wear resistance (two important properties in bearing applications) of bronze SAE660. The melt had prepared by induction furnace. Then, it had poured in sand mold in four different casting conditions, including pouring temperatures of 950 oC and 1200 oC, and cooling with water and air. Finally, the microstructure, hardness and wear resistance of the SAE660 had investigated. The results indicated that if the maximum hardness, along with the minimum weight loss due to wear (or maximum wear resistance) is required; the contents of intermetallic compounds, lead phase and the solid solution phase should be more. In this way, the samples which are cooled in air and poured at 950 oC have the high hardness and the lowest weight loss.
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Internal casting defects that are detected by radiography may also be detected by ultrasonic method. Ultrasonic testing allows investigation of the cross-sectional area of a casting, it is considered to be a volumetric inspection method. The high frequency acoustic energy travels through the casting until it hits the opposite surface or an interface or defect. The interface or defect reflects portions of the energy, which are collected in a receiving unit and displayed for the analyst to view. The pattern of the energy deflection can indicate internal defect. Ultrasonic casting testing is very complicated in practice. The complications are mainly due to the coarse-grain structure of the casting that causes a high ultrasound attenuation. High attenuation then makes it impossible to test the entire volume of material. This article is focused on measurement of attenuation, the effect of probe frequency on attenuation and testing results.
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The casting workshop was discovered with numerous artifacts, confirming the existence of the manufacturing process of metal ornaments using ceramic molds and investment casting technology in Lower Silesia (Poland) in 7-6 BC. The research has yielded significant technological information about the bronze casting field, especially the alloys that were used and the artifacts that were made from them. Based on the analyses, the model alloys were experimentally reconstructed. Taking advantage of the computer-modeling method, a geometric visualization of the bronze bracelets was performed; subsequently, we simulated pouring liquid metal in the ceramic molds and observed the alloy solidification. These steps made it possible to better understand the casting processes from the perspective of the mold technology as well as the melting and casting of alloys.
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In contemporary high-pressure die casting foundries, the mastery of each sequence in the production cycle is more and more important. In the paper, an example of virtual analysis of gearbox casting from Al alloy will be presented. It includes a large variety of parameters, as follows: choosing of appropriate foundry technology, calculation of computer simulation of casting process which takes into account the filling process of cold chamber and filling of cavity, model description of three phases in high-pressure die casting, flow of molten metal, solidification, formation of stress and deformations. Additionally, the optimization of cooling and heating systems will be compared with calculated volume defects, dimensions of castings and their deformations with experimentally obtained values.
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The work presents the results of the investigations of the effect of the nitrogen (N2) refining time „τraf” and the gas output on the course of the crystallization process, the microstructure and the gassing degree of silumin 226 used for pressure casting. The refinement of the examined silumin was performed with the use of a device with a rotating head. The crystallization process was examined by way of thermal analysis and derivative analysis TDA. The performed examinations showed that the prolongation of the N2 refining time causes a significant rise of the temperature of the crystallization end of the silumin, „tL”, as well as a decrease of its gassing degree, „Z”. An increase of the nitrogen output initially causes an increase of the temperature „tL” and a drop of the gassing degree „Z”, which reach their maximal values with the output of 20 dm3 /min. Further increase of the output causes a decrease of the value „tL” and an increase of „Z”. The examined technological factors of the refining process did not cause any significant changes in the microstructure of silumin 226.
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The paper presents the optimization of master alloy amount for the high nodular graphite yield (80-90%) in cast iron obtain in lost foam process. The influence of the gating system configuration and the shape of the reaction chamber, the degree of spheroidisation cast iron was examined. Research has shown that the, optimal of master alloy amount of 1.5% by mass on casting iron. The degree of spheroidisation is also influenced by the gating system configuration. The best spheroidisation effect was obtained for liquid cast iron was fed into the reaction chamber from the bottom and discharged from the top.
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Energy conservation is an important step to overcome the energy crisis and prevent environmental pollution. Casting industry is a major consumer of energy among all the industries. The distribution of electrical energy consumed in all the departments of the foundry is presented. Nearly 70% of the energy is consumed especially in the melting department alone. Production of casting involves number of process variables. Even though lot of efforts has been taken to prevent defects, it occurs in the casting due to variables present in the process. This paper focuses the energy saving by improving the casting yield and by reducing the rejections. Furthermore an analysis is made on power consumption for melting in the induction furnace to produce defective castings and improvement in the casting yield. The energy consumed to produce defective castings in all other departments is also presented. This analysis reveals that without any further investment in the foundry, it is possible to save 3248.15 kWh of energy by reducing the rejections as well as by improving the casting yield. The redesign of the feeding system and the reduced major rejection shrinkage in the body casting improved the casting yield from 56% to 72% and also the effective yield from 12.89% to 66.80%.
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The work presents the effect of strontium and antimony modification on the microstructure and mechanical properties of 226 silumin casts. The performed research demonstrated that strontium causes high refinement of silicon precipitations in the eutectic present in the microstructure of the examined silumin and it significantly affects the morphology of eutectic silicon from the lamellar to the fibrous one. Sr modification also causes an increase of: the tensile strength „Rm” by 12%; the proof stress „Rp0,2” by 5%; the unit elongation „A” by 36% and the hardness HB by 13%. Antimony did not cause a change in the microstructure of the silumin, yet it caused an increase in Rm and HB by 5%, in Rp0,2 by 7% and in A by 4%.
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The article presents an analysis of the applicability of the Replicast CS process as an alternative to the investment casting process, considered in terms of the dimensional accuracy of castings. Ceramic shell moulds were based on the Ekosil binder and a wide range of ceramic materials, such as crystalline quartz, fused silica, aluminosilicates and zirconium silicate. The linear dimensions were measured with a Zeiss UMC 550 machine that allowed reducing to minimum the measurement uncertainty.
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A significant part of the knowledge used in the production processes is represented with natural language. Yet, the use of that knowledge in computer-assisted decision-making requires the application of appropriate formal and development tools. An interesting possibility is created by the use of an ontology that is understandable both for humans and for the computer. This paper presents a proposal for structuring the information about the foundry processes, based on the definition of ontology adapted to the physical structure of the ongoing technological operations that make up the process of producing castings.
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Castability of thin-walled castings is sensitive to variation in casting parameters. The variation in casting parameters can lead to undesired casting conditions which result in defect formation. Variation in rejection rate due to casting defect from one batch to other is common problem in foundries and the cause of this variation usually remain unknown due to complexity of the process. In this work, variation in casting parameters resulting from human involvement in the process is investigated. Casting practices of different groups of casting operators were evaluated and resulting variations in casting parameters were discussed. The effect of these variations was evaluated by comparing the rejection statistics for each group. In order to minimize process variation, optimized casting practices were implemented by developing specific process instructions for the operators. The significance of variation in casting parameters in terms of their impact on foundry rejections was evaluated by comparing the number of rejected components before and after implementation of optimized casting practices. It was concluded that variation in casting parameters due to variation in casting practices of different groups has significant impact on casting quality. Variation in mould temperature, melt temperature and pouring rate due to variation in handling time and practice resulted in varying quality of component from one batch to other. By implementing the optimized casting instruction, both quality and process reliability were improved significantly.
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The current work presents and describes the test bench for analyzing the lost foam process, especially measuring of the pressure of gases in the gas gap and continuous measuring of the rate of rise of the bath level when pouring the liquid metal into the mould. A series of preliminary research was carried out on the bench which was aimed at determining the influence of the basic parameters of the process, i.e. the density of the styrofoam pattern, thickness of the refractory coating applied on the pattern, kind of the alloy and the temperature of pouring on the mould cavity by the liquid metal and the pressure of gases in the gas gap.
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Defects affect the properties and behavior of the casting during its service life. Since the defects can occur due to different reasons, they must be correctly identified and categorized, to enable applying the appropriate remedial measures. several different approaches for categorizing casting defects have been proposed in technical literature. They mainly rely on physical description, location, and formation of defects. There is a need for a systematic approach for classifying investment casting defects, considering appropriate attributes such as their size, location, identification stage, inspection method, consistency, appearance of defects. A systematic approach for categorization of investment casting defects considering multiple attributes: detection stage, size, shape, appearance, location, consistency and severity of occurrence. Information about the relevant attributes of major defects encountered in investment casting process has been collected from an industrial foundry. This has been implemented in a cloud-based system to make the system freely and widely accessible.
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The paper presents the method of preparing a composite slurry composed of AlSi11 alloy matrix and 10 vol.% of SiC particles, as well as the method of its high-pressure die casting and the measurement results concerning the castability of the obtained composite. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. There were found the regression equations describing the change of castability of the examined composite as a function of pressure die casting process parameters. The conclusion gives the analysis and the interpretation of the obtained results.
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Homogeneity of die castings is influenced by wide range of technological parameters as piston velocity in filling chamber of die casting machine, filling time of mould cavity, temperature of cast alloy, temperature of the mould, temperature of filling chamber, surface pressure on alloy during mould filling, final pressure and others. Based on stated parameters it is clear, that main parameters of die casting are filling time of die mould cavity and velocity of the melt in the ingates. Filling time must ensure the complete filling of the mould cavity before solidification process can negatively influence it. Among technological parameters also belong the returning material, which ratio in charge must be constrained according to requirement on final homogeneity of die castings. With the ratio of returning material influenced are the mechanical properties of castings, inner homogeneity and chemical composition.
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Hot tearing severity was evaluated in this experiment by introducing a new apparatus called Constrained Rod Casting Modified Horizontal (CRCM-Horizontal). Six constraint bars with different lengths can produce hot tearing on the cast sample. Mold position was modified from vertical to horizontal and the shape was changed from a harp shape to a star shape, which allows for the liquid metal to feed into each rod cavity simultaneously. Hot tearing development was recorded along the bars by a digital camera. A new Hot Tearing Susceptibility (HTS) formula was developed for quantitative investigation of hot tearing on a cast sample. The parameters of the HTS formula are bar length of cast sample (Li), tear severity (Ci) and location of hot tear (Pi). Footprint charts and hot tear scales are used to illustrate hot tearing severity. The experiment was conducted with Al-1.36Zn-1.19Si and Al-5.9Cu-1.9Mg alloys to investigate the sensibility of the apparatus and modification its operation.
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The effect of cobalt aluminate inoculant addition and melt-pouring temperature on the structure and mechanical properties of Ni-based superalloy was studied. The first major move to control the quality of investment cast blades and vanes was the control of grain size. Cobalt aluminate (CoAl2O4) is the most frequently utilized inoculant in the lost-wax casting process of Ni-based superalloys. The inoculant in the prime coat of moulds and pouring temperature play a significant role in grain size control. The finest surface grains were obtained when the internal surface of shell mould was coated with cobalt aluminate and subsequently pouring was at 1480°C. The influence of selected casting parameters and inoculant addition on mechanical properties was investigated on the basis of tensile, creep and hardness testing. The effect of grain refinement on mechanical properties were consistent with established theories. Tests conducted at ambient temperature indicated a beneficial effect of grain refinement both on tensile strength and hardness. In contrast at elevated temperature during creep, the reverse trend was observed.
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The presented results of investigations are part of a larger study focused on the optimization of the flow and mixing of liquid steel in the industrial tundish of continuous casting machine. The numerical simulations were carried out concern the analysis of hydrodynamic conditions of liquid steel flow in a tundish operating in one of the national steelworks. Numerical simulations were performed using the commercial code ANSYS Fluent. The research concerns two different speeds of steel casting. In real conditions, these speeds are the most commonly used in the technological process when casting two different groups of steel. As a result of computational fluid dynamics (CFD) calculations, predicted spatial distributions of velocity and liquid steel turbulence fields and residence time distribution (RTD) curves were obtained. The volume fractions of different flows occurring in the tundish were also calculated. The results of the research allowed a detailed analysis of the influence of casting speed on the formation of hydrodynamic conditions prevailing in the reactor.
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