Archives of Foundry Engineering

Simplifications used in simulation program codes require the use of substitute parameters in the material databases (also called apparent or substitutive). On the one hand, they formally fit into the records used in the heat flow model, porosity, properties etc. and on the other hand they should be determined in conditions most similar to the real casting-mould system.

The article presents results of a research on thermophysical parameters of gypsum mould used for precision casting moulds. Experiments were carried out on a cylindrical mould made of Plasticast gypsum, in which the heat source was a cylinder filled with liquid aluminium alloy of the temperature of 655°C. Energetic validation was carried out by using the NovaFlow&Solid ver. 6.3 simulation code. As a result of validation tests, substitute thermophysical parameters of gypsum were determined. For determined parameters, best-fit of solidification time from the experiment and simulation was obtained and the curves of gypsum mass heating were satisfactorily recreate.

An overview of the bibliography regarding the connection of knowledge about precious metal alloys and aspects of the use of computer aided technologies to the optimization of the jewelry casting processes is presented. An analysis of the usability of selected CAx systems was made: 1) for spatial design, called Rhinoceros 6 and 2) CAE system: NovaFlow & Solid (NF&S). The authors describe own research including data acquisition and evaluation of temperature variations during solidification of the selected Au-Ag-Cu alloy, with the identification of the phase transformations of this alloy. The intensity of heat exchange was changed (cooling of specimens under ambient temperature conditions – "normal" intensity and with the furnace – very slow cooling). The problem of completing the simulation database was pointed out and analyzed. Examples of simulations of casting selected jewelry (ring and signet) were given and compared with the result of the experiment realized in real conditions. It was confirmed that the optimization by combining experimental and simulation studies allows for the acquisition of new knowledge, and also facilitates the creation of new artistic designs of jewelry as well as performing the feasibility check, and then optimizing the chosen technology.

The article presents the results of permeability measurements of a zirconium alcohol coating applied on moulds and cores. The introduction extensively discusses the reasons for the application of protective coatings, as well as their advantages and disadvantages. Also, the problems related to the application of protective coatings are presented i.e. limited permeability and thus the possibility of the presence of gas-originated defects in the casts. Next, the paper discusses the methods of measuring the permeability of protective coating proposed by Falęcki and Pacyniak. The study also presents an indirect permeability measurement method. For the investigations, zirconium alcohol coatings with the three conventional viscosities 10, 20 and 30s were used. The viscosity was determined by means of the Ford cup with the clearance of 4mm. The coatings were applied onto profiles of Φ 50 x 50 mm, made of moulding sand consisting of a sand matrix with the mean grain size of dL = 0,11, 17, 24, 31 and 34 mm and phenol-formaldehyde resin. The effect of the matrix grain size on the permeability of the sand with and without a coating was determined.

The paper presents the results of investigations concerning the influence of gray cast iron modification on free vibration frequency of the disc casting. Three different chemical composition melts of gray cast iron were prepared in induction furnace. During gravity casting 0.05% and 0.3% mass of the Inolate modifier was added on stream of metal for changing graphite flakes in castings. Sound signal vibration of cast iron sample was registered by means on microphone for free vibration frequency measurements. Decreasing of free vibration frequency of modified cast iron in comparison with non modified castings was observed. Higher contents of modifier causes more decreasing of free vibration frequency. Cast iron with smaller contents of carbon and silicon have higher free vibration frequency in comparison with eutectic composition cast iron. Hardness of examined cast iron is lower when the more modifier is added during modification process. Free frequency is smaller with smaller Brinell hardness of disc casting. It was concluded that control of free vibration frequency of disc castings by means of chemical composition and modification process can improved comfort and safety of working parts.

The objective of the study reported in this paper was to determine the effect of structure on thermal power of cast-iron heat exchangers which in this case were furnace chambers constituting the main component of household fireplace-based heating systems and known commonly as fireplace inserts. For the purpose of relevant tests, plate-shaped castings were prepared of gray iron with flake graphite in pearlitic matrix (the material used to date typically for fireplace inserts) as well as similar castings of gray cast iron with vermicular graphite in pearlitic, ferritic-pearlitic, and ferritic matrix. For all the cast iron variants of different structures (graphite precipitate shapes and matrix type), calorimetric measurements were carried out consisting in determining the heat power which is quantity representing the rate of heat transfer to the ambient environment. It has been found that the value of the observed heat power was affected by both the shape of graphite precipitates and the type of alloy matrix. Higher thermal power values characterize plate castings of gray iron with vermicular graphite compared to plates cast of the flake graphite gray iron. In case of plates made of gray cast iron with vermicular graphite, the highest values of thermal power were observed for castings made of iron with ferritic matrix.

The problem of harmful casting resins has been present in foundries for many years. Manufacturers are introducing new products that contain in their composition environmentally and eco-friendly ingredients. Unfortunately, not all types of technology can be used, sometimes environmental benefits are disproportionate to the quality of castings and their price. In the foundry industry, the most popular binders are based on organic compounds (often carcinogenic) and other harmful substances. Due to strict legal regulations regarding environmental protection, as well as care for the foundry's workers' comfort - their occurrence should be reduce to a minimum. These compounds often behave also depending on the conditions of use (temperature, atmosphere). The application of various methods of thermal analysis and spectroscopic methods allows to verify the mechanism of resin decomposition process in relation to conditions in the form in both inert and oxidizing atmosphere. For analysis the resins from cold-box technology, were used TG–DTG–DSC, Py-GC/MS methods and specified the course of changes occurring in combination of different atmosphere.

Presented paper shows the mathematical and numerical approaches for modelling of binary alloy solidification solved by the Finite Element Method (FEM). The phenomenon of shrinkage cavities formation process is included in the numerical model. Multiple macroscopic cavities can be modelled within the single casting volume. Solid, liquid and gaseous phases with different material properties are taken into account during solidification process. Mathematical model uses the differential equation of heat diffusion. Modification of specific heat is used to describe the heat releasing during liquid-solid phase change. Numerical procedure of shrinkage cavities evolution is based on the recognition of non-connected liquid volumes and local shrinkage computation in the each of them. The recognition is done by the selection of sets of interconnected nodes containing liquid phase in the finite element mesh. Original computer program was developed to perform calculation process. Obtained results of temperature and shrinkage cavities distributions are presented and discussed in details.

The paper presents a production scheduling problem in a foundry equipped with two furnaces and one casting line, where the line is a bottleneck and furnaces, of the same capacity, work in parallel. The amount of produced castings may not exceed the capacity of the line and the furnaces, and their loads determine metal type from which the products are manufactured on the casting line. The purpose of planning is to create the processing order of metal production to prevent delays in the delivery of the ordered products to the customers. The problem is a mix of a lot-sizing and scheduling problems on two machines (the furnaces) run in parallel. The article gives a mathematical model that defines the optimization problem, and its relaxed version based on the concept of a rolling-horizon planning. The proposed approaches, i.e. commercial solver and Iterated Local Search (ILS) heuristic, were tested on a sample data and different problem sizes. The tests have shown that rolling horizon approach gives the best results for most problems, however, developed ILS algorithm gives better results for the largest problem instances with tight furnace capacity.

This article presents the preparation of composite casts made using the technology of precise casting by the method of melted models. The composite was reinforced with the ceramic sinter from Al2O3 particle shaped in a printed polystyrene female mould, which was fired together with precured ceramics. The resulting ceramic preform, after being saturated with paraffin and after the filling system is installed, was filled with liquid moulding sand and fired together with the mould. The reinforcement was saturated by means of the counter-pressure exerting action on the metal column, being a resultant of pressures inside and outside the chamber. The preliminary assessment showed no apparent defects in the shape of the cast. The casting was measured and the figures were compared with the dimensions of the matrix in which the reinforcing preform was made, the preform after firing and after saturation with paraffin. The results were presented in a table and dimensional deviations were determined. The composite casting was subjected to metallographic tests, which excluded any porous defects or damage to the reinforcement. It can therefore be said that, according to the predictions resulting from the previous calculations, the pressure values used allowed for complete filling of the reinforcement capillaries. The proposed method is therefore suitable for the preparation of precision composite castings with complex shapes.

A significant development of the foundry industry contributes to the creation of high reliability and operational strength castings so that they meet specific standards in accordance with customers’ needs. This technology, however, is inseparably connected with casting defects in finished products. Cast products are subject to various defects which are considered acceptable or not, which is conditioned by the alloy chemical composition and strength characteristics, that is, generally – qualities to be agreed between the foundry and the customer. It is the latter that led the authors to research on designing a tool enabling the most reliable possible assessment of the emerging casting defects, which after proper consultations can be repaired and the casting – sold. The paper presents an original tool named the Open Atlas of Defects (OAD), developed for the last few years to support the evaluation of cast iron defects using Non-Destructive Testing (NDT) casting defects analysis tools (DCC card – Demerit Control Chart, Pareto-Lorenz analysis and ABC analysis). The OAD tool structure was presented as an integral part of the original system module for acquisition and data mining (A&DM) in conjunction with the possibilities of using selected tools for defect analysis support on the example of cast iron casting.

For quality grey cast iron production, the challenging issues are to avoid cementite structure and obtain the desired graphite morphology with proper matrix as well as hardness. The objective of the present research is to find out the right combination of preconditioner and inoculant that may help to overcome the challenges. In this work, sulphur content is kept low (0.01%). Two preconditioners namely metallurgical SiC and zirconium bearing FeSi with two types of inoculant are individually used to make four combinations of sample and for each case metal is poured into the green sand mould. Finally Brinell hardness and graphite morphology is observed in the thickest and thinnest portions of the castings. Metallurgical SiC with barium bearing inoculant gives better graphite morphology and hardness than strontium bearing inoculant, on the other hand zirconium bearing FeSi gives more satisfying result than SiC with every type of inoculant. Among all of the combinations Zr bearing preconditioner with Ba bearing inoculant gives good graphite morphology with best mechanical properties in both thickest and thinnest portions of the casting.

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 paper presents the results of experimental-numerical tests of firing at aluminum composite materials. The test materials were manufactured by pressure infiltration of porous ceramic preforms made of -Al2O3 particles in the amount of 30% and 40% by volume. The EN AW-7075 alloy was chosen as the material matrix, and the steel 7.62×39 mm (M 43) FMJ (Full Metal Jacket) intermediate ammunition was selected for firing. In the result of the experiment, the samples were perforated with a clear difference in the muzzle diameter. The projectile with fragments caused damage to up to three reference plates placed behind the samples (witness plates) in composites with 40% of particles by volume. The mechanics of crack propagation during ballistic impacts of the projectile was characterized based on microstructure studies. Then, using numerical analysis of impact load, the examination of composite materials puncture in the ABAQUS environment was carried out. The Finite Element Method (FEM) was employed for the discretization of geometric models using Hex elements. The Johnson-Cook constitutive model describing the relationship between stress and strain in metal-ceramic composites was applied for the analyses. Numerical models were then subjected to numerical verification using smoothed particle hydrodynamics (SPH). Based on the obtained results, it was found that the hybrid FEM/SPH method correlates significantly with the experimental results.

Monitoring the solidification process is of great importance for understanding the quality of the melt, for controlling it, and for predicting the true properties of the alloy. Solidification is accompanied by the development of heat, the magnitude of which depends on the different phases occurring during solidification. Thermal analysis is now an important part of and tool for quality control, especially when using secondary aluminium alloys in the automotive industry. The effect of remelting on the change of crystallization of individual structural components of experimental AlSi9Cu3 alloy was determined by evaluation of cooling curves and their first derivatives. Structural analysis was evaluated using a scanning electron microscope. The effect of remelting was manifested especially in nucleation of phases rich in iron and copper. An increasing number of remelts had a negative effect after the fourth remelting, when harmful iron phases appeared in the structure in much larger dimensions.

In order to identify the influence of different Mn, Cd, V and Zr content on the properties of Al-Cu casting alloys in hydraulic valves, orthogonal test methods were used to prepare alloy test bars with different elements and contents. Tensile tests were performed on the test bars so obtained. The microstructure of alloys with different compositions is studied. The results show that adding approximately 0.4% of Mn can not only form a strengthening phase but also reduce the excessive segregation of the matrix along the grain boundary. A Cd content of 0.2% can promote the formation of micro Cd spheres in the softer aluminum matrix. Hard spots increase the wear resistance of the material; however, an excess of Cd will cause element segregation and deteriorate the mechanical properties of the valve body. Zr and V refine the grains in the alloy; however, an excess of these elements will lead to a large area of segregation. If proper heat treatment is lacking, the mechanical properties of the valve body deteriorate.

Consecutive casting of bimetallic applies consecutive sequences of pouring of two materials into a sand mold. The outer ring is made of NiHard1, whereas the inner ring is made of nodular cast iron. To enable a consecutive sequence of pouring, an interface plate made of low carbon steel was inserted into the mold and separated the two cavities. After pouring the inner material at the predetermined temperature and the interface had reached the desired temperature, the NiHard1 liquid was then poured immediately into the mold. This study determines the pouring temperature of nodular cast iron and the temperature of the interface plate at which the pouring of white cast iron into the mold should be done. Flushing the interface plate for 2 seconds by flowing nodular cast iron liquid as inner material generated a diffusion bonding between the inner ring and interface plate at pouring temperatures of 1350 °C, 1380 °C, and 1410 °C. The interface was heated up to a maximum temperature of 1242 °C, 1260 °C, and 1280 °C respectively. The subsequent pouring of white cast iron into the mold to form the outer ring at the interface temperature of 1000 °C did not produce a sufficient diffusion bonding. Pouring the outer ring at the temperature of 1430°C and at the interface plate temperature of 1125 °C produced a sufficient diffusion bonding. The presence of Fe3O2 oxide on the outer surface of the interface material immediately after the interface was heated above 900 ⁰C has been identified. Good metallurgical bonding was achieved by pouring the inner ring at the temperature of 1380°C, interface temperature of 1125 °C and then followed by pouring of the outer ring at 1430⁰C and flushing time of 7 seconds.

This paper presents the problems related to smelting gray and ductile cast iron. Special attention is paid to the metallurgical quality of cast iron. It depends on the type of furnace, charge materials and the special combination of charge, overheating and holding temperature, melting time, modification and spheroidization method. The evaluation of metallurgical quality has been performed by using derivativethermal analysis (DTA). During the smelting process and secondary metallurgy, the ITACA system was used allowing to obtain information on alloy characteristic temperatures (Tliquidus, TeMin, TeMax, Tsolidus), VPS value, recalescence value, IGQ coefficient, nucleation gauge, porosity etc. The results of investigations and calculations are displayed in the form of graphs and dependencies. It has been shown that the derivative-thermal analysis (DTA) is an effective complement of chemical analysis and it has been found that both the increase in temperature and metal holding time have a negative impact on the metallurgical quality of liquid metal. The metallurgical quality can be improved by using proper composition of charge materials and modifiers.

Bentonites and clays are included in the group of drilling fluids materials. The raw materials are mainly clay minerals, which are divided into several groups, like montmorillonite, kaolinite, illite, biotite, muscovite, nontronite, anorthoclase, microcline, sanidine or rutile, differing in chemical composition and crystal lattice structure. Clay minerals have a layered structure forming sheet units. The layers merge into sheets that build up to form the structure of the mineral.

The aim of the studies carried out in the ŁUKASIEWICZ Research Network - Foundry Research Institute is to explore the possibility of using minerals coming from Polish deposits.

The article outlines the basic properties of hybrid bentonites, which are a mixture of bentonite clay called beidellite, originating from overburden deposits of the Turoszów Mine, and foundry bentonite from one of the Slovak deposits. As part of the physico-chemical tests of minerals, measurements included in the PN-85/H-11003 standard, i.e. montmorillonite content, water content and swelling index, were carried out. Additionally, the loss on ignition and pH chemical reaction were determined. Based on the thermal analysis of raw materials, carried out in the temperature range from 0 to 1000oC, changes occurring in these materials during heating, i.e. thermal stability in contact with liquid metal, were determined.

Examinations of the sand mixture based on pure clay and bentonite and of the sand mixture based on hybrid bentonites enabled tracing changes in permeability, compressive strength and tensile strength in the transformation zone as well as compactability referred to the clay content in sand mixture. Selected technological and strength parameters of synthetic sands are crucial for the foundry, because they significantly affect the quality of the finished casting.

Based on the analysis of the results, the optimal composition of hybrid bentonite was selected.

The paper deals with the effect of heating of various prepared batch materials into semisolid state with subsequent solidification of the cast under pressure. The investigated material was a subeutectic aluminium alloy AlSi7Mg0.3. The heating temperature to the semisolid was chosen at 50% liquid phase. The used material was prepared in a variety of ways: heat treatment, inoculation and by squeeze casting. Also the influence of the initial state of material on inheritance of mechanical properties and microstructure was observed. The pressure was 100 MPa. Effect on the resulting casting structure, alpha phase distribution and eutectic silicon was observed. By using semisolid squeeze casting process the mechanical properties and microstructures of the casts has changed. The final microstructure of the casts is very similar to the microstructure that can be reached by technology of thixocasting. The mechanical properties by using semisolid squeeze casting has been increased except the heat treated material.

The article presents investigation results of the effect of sand fluidization on the structure and mechanical properties of AlSi9 aluminum alloy. Castings were made by lost foam casting process with sand fluidization in mold at the stages of their solidification and cooling. Sand fluidization was achieved by blowing sand bed with compressed air in a foundry container. The metallographic study was carrying out on samples cut from different sections of the castings. Mechanical properties were determined on specimens made from cast samples. Microstructural analysis showed that sand fluidization increases the cooling rate, as a result, the main microstructural components of the alloy – SDAS, eutectic silicon and needles of the rich-iron phase – decrease. Moreover, in different sections of the casting structure is more uniform. With an increasing the air flow rate, a greater refinement of the structure is observed. Through the use of sand fluidization, the mechanical properties of LFC aluminum alloys increase to the level of gravity die castings.