The paper deals with the impact of technological parameters on the heat transfer coefficient and microstructure in AlSi12 alloy using squeeze casting technology. The casting with crystallization under pressure was used, specifically direct squeeze casting method. The goal was to affect crystallization by pressure with a value 100 and 150 MPa. The pressure applied to the melt causes a significant increase of the coefficient of heat transfer between the melt and the mold. There is an increase in heat flow by approximately 50% and the heat transfer coefficient of up to 100-fold, depending on the casting conditions. The change in cooling rate influences the morphology of the silicon particles and intermetallic phases. A change of excluded needles to a rod-shaped geometry with significantly shorter length occurs when used gravity casting method. By using the pressure of 150 MPa during the crystallization process, in the structure can be observed an irregular silica particles, but the size does not exceed 25 microns.
The paper presents the research results of horizontal continuous casting of ingots of aluminium alloy containing 2% wt. silicon (AlSi2). Together with the casting velocity (velocity of ingot movement) we considered the influence of electromagnetic stirring in the area of the continuous casting mould on refinement of the ingot’s primary structure and their selected mechanical properties, i.e. tensile strength, yield strength, hardness and elongation. The effect of primary structure refinement and mechanical properties obtained by electromagnetic stirring was compared with refinement obtained by using traditional inoculation, which consists in introducing additives, i.e. Ti, B and Sr, to the metal bath. On the basis of the obtained results we confirmed that inoculation done by electromagnetic stirring in the range of the continuous casting mould guarantees improved mechanical properties and also decreases the negative influence of casting velocity, thus increasing the structure of AlSi2 continuous ingots.
Substituting of ethyl silicate with ecologic sols of colloidal silica in the investment casting technology, resulting from the increased demands concerning environmental protection, caused the prolongation of production cycle for precision castings produced in multi-layer thin-walled ceramic shell moulds. Modification of Sizol 030 binder with benzoyl peroxide, proposed in the paper, was aimed at restriction of time needed for realization of a single layer of the shell mould, and by the same, of such a mould as a whole. Examination of kinetics of the drying process were held for the layers made of prepared moulding material and the influence of binder modification on the mould curing time was determined.
Metal casting process involves processes such as pattern making, moulding and melting etc. Casting defects occur due to combination of various processes even though efforts are taken to control them. The first step in the defect analysis is to identify the major casting defect among the many casting defects. Then the analysis is to be made to find the root cause of the particular defect. Moreover, it is especially difficult to identify the root causes of the defect. Therefore, a systematic method is required to identify the root cause of the defect among possible causes, consequently specific remedial measures have to be implemented to control them. This paper presents a systematic procedure to identify the root cause of shrinkage defect in an automobile body casting (SG 500/7) and control it by the application of Pareto chart and Ishikawa diagram. with quantitative Weightage. It was found that the root causes were larger volume section in the cope, insufficient feeding of riser and insufficient poured metal in the riser. The necessary remedial measures were taken and castings were reproduced. The shrinkage defect in the castings was completely eliminated.
The method of pressure die casting of composites with AlSi11 alloy matrix reinforced with 10 vol. % of SiC particles and the analysis of the distribution of particles within the matrix is presented. The composite castings were produced at various values of the piston velocity in the second stage of injection, at diverse intensification pressure values, and various injection gate width values. The distribution of particles over the entire cross-section of the tensile specimen is shown. The index of distribution was determined on the basis of particle count in elementary measuring fields. The regression equation describing the change of the considered index was found as a function of the pressure die casting parameters. The conclusion presents an analysis of the obtained results and their interpretation.
Diagnostics of composite castings, due to their complex structure, requires that their characteristics are tested by an appropriate description method. Any deviation from the specific characteristic will be regarded as a material defect. The detection of defects in composite castings sometimes is not sufficient and the defects have to be identified. This study classifies defects found in the structures of saturated metallic composite castings and indicates those stages of the process where such defects are likely to be formed. Not only does the author determine the causes of structural defects, describe methods of their detection and identification, but also proposes a schematic procedure to be followed during detection and identification of structural defects of castings made from saturated reinforcement metallic composites. Alloys examination was conducted after technological process, while using destructive (macroscopic tests, light and scanning electron microscopy) and non-destructive (ultrasonic and X-ray defectoscopy, tomography, gravimetric method) methods. Research presented in this article are part of author’s work on castings quality.
A cast iron is gradient material. This means that depending on the cooling rate it is possible, at the same chemical composition and the physicochemical state of molten metal, to obtain material with a different structure. The connection between the wall thickness of the casting and the speed of its cooling expresses the casting module. Along with the module escalation a cooling rate of the casting is reducing what can cause changes of the microstructure and the increased tendency to the crystallization of distorted graphite forms. Inspections of experimental castings from nodular cast iron with different modules were conducted to the graphite form.
Metallic foams are materials of which the research is still on-going, with the broad applicability in many different areas (e.g. automotive industry, building industry, medicine, etc.). These metallic materials have specific properties, such as large rigidity at low density, high thermal conductivity, capability to absorb energy, etc. The work is focused on the preparation of these materials using conventional casting technology (infiltration method), which ensures rapid and economically feasible method for production of shaped components. In the experimental part we studied conditions of casting of metallic foams with open pores and irregular cell structure made of ferrous and nonferrous alloys by use of various types of filler material (precursors).
In paper is presented results of studies concerning ingot of Al with a purity of 99.5% cast with use of stand of horizontal continuous casting. Mainly together with casting velocity was considered influence of electromagnetic stirrer, which was placed in continuous casting mould on refinement of ingots structure and theirs usability to plastic deformation. Effect of structure refinement and usability to plastic deformation obtained by influence of electromagnetic stirring was compared with refinement obtained by use of traditional inoculation, which consists in introducing of additives i.e. Ti and B to metal bath. On the basis of obtained results was affirmed that inoculation realized by electromagnetic stirring in range of continuous casting mould guarantees improvement in structure refinement and usability to rolling of pure Al continuous ingots.
In paper is presented idea of construction and influence of selected parts of stand of horizontal continuous casting on quality of pure Al and AlSi2 alloy ingots. The main parts of the made stand belong to induction furnace, which is also tundish, water cooled continuous casting mould, system of recooling, system of continuous ingot drawing and cutting. Mainly was considered influence of electromagnetic stirrer, which was placed in continuous casting mould on refinement of ingots structure. Effect of structure refinement obtained by influence of electromagnetic stirring was compared with refinement obtained by use of traditional inoculation, which consists in introducing of additives i.e. Ti and B to metal bath. The results of studies show possibility of effective refinement of Al and AlSi2 alloy primary structure, only with use of horizontal electromagnetic field and without necessity of application of inoculants. This method of inoculation is important, because inoculants decrease the degree of purity and electrical conductivity of pure aluminum and moreover are reason of point cracks formation during rolling of ingots.
The measurement results concerning the abrasive wear of AlSi11-SiC particles composites are presented in paper. The method of preparing a composite slurry composed of AlSi11 alloy matrix and 10, 20% vol.% of SiC particles, as well as the method of its highpressure die casting was described. Composite slurry was injected into metal mould of cold chamber pressure die cast machine and 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. Very good uniform arrangement of SiC particles in volume composite matrix was observed and these results were publicated early in this journal. The kinetics of abrasive wear and correlation with SiC particles arrangement in composite matrix were presented. Better wear resistance of composite was observed in comparison with aluminium alloy. Very strong linear correlation between abrasive wear and particle arrangement was observed. The conclusion gives the analysis and the interpretation of the obtained results.
Nowadays, there are growing demands on the accuracy of production. Most of this is reflected in precise manufacturing, such as the investment casting process. Foundries are looking for causes of defects in some cases for a very long time, and it may happen that the source of defects is completely different from what was originally assumed. During the casting process there exist potential causes of defects as oxygen inclusions. This paper represents a summary of the beginnings of a wider research that will address the problems of gating systems in investment casting technology. In general, the influence of the melt flow is underestimated and the aim of the whole scientific research is to demonstrate the significant influence of laminar or turbulent flow on the resulting casting quality. Specifically, the paper deals with the analysis of the most frequent types of defects found in castings made of expensive types of materials casted in an open atmosphere and demonstration of connection with the design of gating systems in the future.
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 tensile strength, the yield point, the elongation and hardness 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 mechanical properties 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.
The results of testing of the selected group of wax mixtures used in the investment casting technology, are presented in the paper. The measurements of the kinetics of the mixtures shrinkage and changes of viscous-plastic properties as a temperature function were performed. The temperature influence on bending strength of wax mixtures was determined.
Casting quality depends on many factors including the quality of the input materials, technology, material securing and last but not least, the mould into which the casting is casted. By pouring into a single-shot mould, based mainly on 1st generation binders, is is a very important factor. Basically, a bentonite mixture represents either a three- or four-component system, but each component of the system is a heterogeneous substance. This heterogeneity punctuates mainly a non-stationary heat field, presented throughout the whole process of the casting production. The most important component is a binder and in the case of first generation binders mostly bentonites are used - clays that contain minimum of 80% of montmorillonite
The powerful tool for defect analysis is an expert system. It is a computer programme based on the knowledge of experts for solving the quality of castings. We present the expert system developed in the VSB-Technical University of Ostrava called ‘ESWOD’. The ESWOD programme consists of three separate modules: identification, diagnosis / causes and prevention / remedy. The identification of casting defects in the actual form of the system is based on their visual aspect.
First part of the article describes how we can by change of gating system achieve better homogeneity of product made by investment casting. Turbine engine flap was made by investment casting technology – lost wax casting. The casting process was realised in vacuum. The initial conditions (with critical occurrence of porosity) was simulated in ProCAST software. Numerical simulation can clarify during analysis of melt turbulent flow in gate system responsible for creation of entrained oxide films. After initial results and conclusions, the new gating system was created with subsequent turbulence analysis. The new design of gating system support direct flow of metal and a decrease of porosity values in observed areas was achieved. Samples taken from a casting produced with use of newly designed gating system was processed and prepared for metallography. The second part of article deals with identification of structural components in used alloy - Inconel 718. The Ni – base superalloys, which are combined unique physical and mechanical properties, are used in aircraft industry for production of aero engine most stressed parts, as are turbine blades.
The paper presents the research results of the influence of the precipitation hardening on hardness and microstructure of selected Al-Si and Al-Cu alloys obtained as 30 mm ingots in a horizontal continuous casting process. The ingots were heat treated in process of precipitation hardening i.e. supersaturation with subsequent accelerated or natural ageing. Moreover in the range of the study it has been carried out investigations of chemical constitution, microscopic metallographic with use of scanning electron microscope with EDS analysis system, and hardness measurements using the Brinell method. On basis of obtained results it has been concluded that the chemical constitution of the investigated alloys enables to classify them into Al alloys for the plastic deformation as EN AW-AlSi2Mn (alternatively cast alloy EN AC-AlSi2MgTi) and as EN AW-AlCu4MgSi (alternatively cast alloy EN AC-AlCu4MgTi) grades. Moreover in result of applied precipitation hardening has resulted in the precipitation from a supersaturated solid solution of dispersive particles of secondary phases rich in alloying element i.e. Si and Cu respectively. In consequence it has been obtained increase in hardness in case of AlSi2Mn alloy by approximately 30% and in case of AlCu4MgSi alloy by approximately 20% in comparison to the as-cast state of continuous ingots.
One of the methods to prevent unsuitable lubrication of moving components of devices and machinery is using bi-metal and three-metal bearings. Centrifugal casting process is one of the manufacturing methods that is used for such bearings. In this study, the purpose is microstructure evaluation of the bonding location and length determination of diffusion bond in structural steel-bronze. A mold made of structural steel with inner diameter of 240mm, length of 300mm and thickness of 10mm was coated by a 6mm film of bronze under centrifugal casting process. At first, a bronze ingot with dimension of 5mm×10mm×20mm is located inside of the hollow cylindrical mold and then the two ends of it will be sealed. During mold rotation with the rate of 800 rpm, two high power flames are used for heating the mold under Ar gas atmosphere to melt the bronze ingot at 1000˚C. After 15minutes, the system is cooled rapidly. Results showed that the diffusion bonding of bronze in structural steel to depth of 1.2µm from the bonding line was obtained. In this bonding, copper element was diffused to 50% of its initial concentration.
The article contains basic information associated with the impact of the FSW process parameters on the forming of a weld while friction welding of aluminium casting alloys. Research was conducted using specially made samples containing a rod of casting alloy mounted in the wrought alloy in the selected area of FSW tool acting. Research has thrown light on the process of joining materials of significantly dissimilar physical properties, such as casting alloys and wrought alloys. Metallographic testing of a weld area has revealed the big impact of welding conditions, especially tool rotational speed, on the degree of metal stirring, grain refinement and shape factor of a weld. As the result of research it has been stated that at the high tool rotational speed, the metals stirring in a weld is significantly greater than in case of welding at low rotational speeds, however this fails to influence the strength of a weld. Plastic strain occurring while welding causes very high refinement of particles in the tested area and changing of their shape towards particles being more equiaxial. In the properly selected welding conditions it is possible to obtain joints of correct and repeatable structure, however in the case of the accumulation of cavities in the casting alloy the FSW process not always eliminates them.
The paper presents the results of investigation into the technological possibility of making light-section castings of GX2CrNiMoN25-6-3 cast steel. For making castings with a wall thickness in the thinnest place as small as below 1 mm, the centrifugal casting technology was employed. The technology under consideration enables items with high surface quality to be obtained, while providing a reduced consumption of the charge materials and, as a result, a reduction in the costs of unit casting production.
Investment casting technology that utilizes lost-wax casting is one of the most-important achievements of ancient society. In Lower Silesia, Poland (Grzybiany, Legnica county), a 7-6 BC casting workshop was discovered with numerous artifacts, confirming the existence of the manufacturing process of metal ornaments using ceramic molds. The paper presents the research of molds and casts from the Bronze and Early Iron Ages. Microscopic analyses of the casting molds were performed, along with radiographic and chemical composition tests of the artifacts (the latter employing the use of the X-ray fluorescence spectroscopy method). The clustering method was used for alloy classification. The microstructure was analyzed by means of Scanning Electron Microscopy with Energy Dispersive Spectroscopy. Conclusions from the research were utilized in further experiments
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.
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).
The FMEA (Failure Mode and Effects Analysis) method consists in analysis of failure modes and evaluation of their effects based on determination of cause-effect relationships for formation of possible product or process defects. Identified irregularities which occur during the production process of piston castings for internal combustion engines were ordered according to their failure rates, and using Pareto-Lorenz analysis, their per cent and cumulated shares were determined. The assessments of risk of defects occurrence and their causes were carried out in ten-point scale of integers, while taking three following criteria into account: significance of effects of the defect occurrence (LPZ), defect occurrence probability (LPW) and detectability of the defect found (LPO). A product of these quantities constituted the risk score index connected with a failure occurrence (a so-called “priority number,” LPR). Based on the observations of the piston casting process and on the knowledge of production supervisors, a set of corrective actions was developed and the FMEA was carried out again. It was shown that the proposed improvements reduce the risk of occurrence of process failures significantly, translating into a decrease in defects and irregularities during the production of piston castings for internal combustion engines.