Jana Sviželová

The article focuses on the mechanical properties of mould parts created using 3D printing technology, for use in the production of castings by High-Pressure Die Casting (HPDC). The mould shapes produced by 3D printing technology bring innovative approaches to optimising production processes. H13 tool steel is widely used for its excellent mechanical properties and resistance to thermal stress. The study focuses on the comparison of the mechanical properties of mould parts produced by traditional methods and 3D printing, with emphasis on their strength, hardness and wear resistance under repeated working cycles. The experimental part includes roughness measurements and tests of mechanical properties, which provide important data on the ability of these components to withstand high mechanical loads and temperature fluctuations during the HPDC process. The results of the study show the advantages and limitations of 3D printing compared to traditional manufacturing processes and give insight into the use of additive technologies in industrial manufacturing. Specifically, the study identified clear quantitative differences in mechanical properties: the 3D printed mould parts had comparable ultimate tensile strength and yield strength to conventionally manufactured parts, but significantly lower ductility (below 1% compared to about 20% in traditional parts) due to higher porosity (0.25–0.30% compared to 0.03–0.04%). Additive mould parts exhibited higher hardness (approximately 510 HV) compared to conventional parts (approximately 450 HV). Surface roughness of the 3D printed parts was more variable, highlighting the need for optimising printing parameters. Thus, additive technology offers benefits in stable hardness and comparable strength, albeit at the expense of reduced ductility and increased variability in surface quality. The research also includes an analysis of the effect of repetitive loading on the mechanical properties of the mould parts made of H13, which provides valuable information for improving their durability and reliability in practice. This research contributes to the development of 3D printing technologies in the field of HPDC and offers new opportunities for improving the efficiency and quality of manufacturing processes in industrial applications.

A physical model of a foundry degassing unit (FDU) uses a simplified approach to melt modelling and degassing. While maintaining the realistic geometry of the rotor, the shape and size of the refining ladle, and the type and amount of inert gas, the original melt is replaced by water. The experimentally evaluated quantity is the degassing efficiency of the melt. Assessing the flow and pressure characteristics in the refining ladle is very complicated experimentally, and it is necessary to use numerical modelling. Numerical modelling of multiphase flow allows the identification, comparison, and quantification of individual flow and pressure characteristics, which can be verified by mutual correlation on basic experimental measurements. Validation of the numerical model is crucial both from the point of view of comparing different states and from the point of view of more advanced multiphase simulations based on this basic model. This article aims to describe the basic numerical model of multiphase flow using the Volume of Fluid (VOF) method for the physical model of the FDU and its verification against experimental measurements.

The paper deals with monitoring the quality of a shaped part of a mould made from H13 tool steel using additive manufacturing. The shaped part of the mould is a key element in the casting of aluminium alloys by high pressure die casting (HPDC) technology and has a major influence on achieving the desired quality of the casting. This paper presents an evaluation methodology which includes the results of surface quality analysis and dimensional accuracy and stability of additively manufactured parts. These analyses were carried out from the production of the mould part to its application in the foundry operating conditions. The comprehensive analyses offer an overall view of the changes caused by individual technological operations. These operations are additive manufacturing, heat treatment, machining, and final coating before implementation into the operating conditions of the foundry. The paper also describes monitoring the quality of the mould part in regular cycles during the production of aluminium castings. This methodology and the results provide new insights in the field of engineering metallurgy.

The paper describes the design of conformal cooling of an aluminium die-casting mold component using numerical simulations along with validation under industrial conditions. The subject of modifications was the insert. The insert comes into direct contact with the metal during the filling of the mold and solidification of the casting and determines the internal shape of the casting. The aim was to optimize the operating temperatures of the insert, reduce thermal stress in the most exposed area, achieve a more even distribution of temperatures in its volume, and maintain the casting quality. Shape modifications were made by topology optimization to reduce the volume of the insert and achieve material savings. 3D printing was chosen as the production technology due to the wider possibilities regarding the variability of the shape of the internal cooling channels. Three geometric designs of the insert were created, and numerical simulations of the temperature field of the mold were carried out in ProCAST software for each variant. Numerical simulations were validated through the temperature field of the mold detected by a thermal camera during the casting cycle. Based on the results, the final design D was selected, for which a complete numerical simulation was performed, including the filling and solidification of the castings. The results were compared with the original variant A. By adjusting the cooling, temperatures were reduced in the most temperature-exposed area of the insert. The new insert variant D showed higher temperatures in the rest of the volume, resulting from material volume reduction. However, the temperatures became even, and the temperature gradients that existed in the original insert variant A were reduced. The simulation also showed that changes in the temperature field of variant D will not negatively affect the quality of the castings. The component will be manufactured and tested in operational conditions in the next research phase.

The paper presents the results of dimensional and shape analysis of additively manufactured shaped parts of foundry moulds; specifically, shaped gate valve inserts made of DIEVAR steel used in the die-casting process of aluminium alloys. The paper aims to provide a comprehensive overview of dimensional and shape analysis during the manufacturing of shaped mould parts before their use in foundry operating conditions. The manufacturing operations include additive manufacturing, heat treatment, machining, and applying a protective coating. Based on these technological operations, the required component accuracy is achieved before application in the operating conditions. The dimensional and shape analysis was measured by 3D scanning and 3D measuring methodology on a coordinate measuring machine. The ROMER ABSOLUTE ARM 3D scanning arm and the THOME PRÄZISION coordinate measuring machine were used for the measurements. The paper presents findings in the development and application of additive manufacturing technologies in engineering metallurgy.

The present paper describes a comparison of the efficiency of different types of rotors used in the refining of aluminium melt at a foundry degassing unit (FDU). Physical modelling was used to obtain data for six different rotor types under defined experimental conditions. In order to evaluate the data from the physical model, an evaluation method based on the interpolation of degassing curves was developed in such a way that the resulting characteristic can be expressed by a single parameter. Using the new methodology, the datasets were replaced by a single dimensionless parameter, a, which characterizes the rotor performance at a given gas flow rate. Based on the comparison of these performance parameters, it was possible to mutually compare the rotor efficiency depending on the selected conditions. The comparison is also demonstrated on the expected degassing time to a certain required concentration. Based on the physical model results, the study found that rotor D had the highest degassing efficiency, followed by rotors F and A. Rotors B and E had similar efficiency at a flow rate of 17 Nl·min⁻¹. However, rotor B showed better efficiency at higher inert gas flow rates (19 and 21 Nl·min⁻¹), while rotor E showed better efficiency at lower flow rates (13 and 15 Nl·min⁻¹).

Foundry Degassing Units (FDU) are used for refining aluminum alloys. For an ideal refining process using an FDU unit, it is necessary to select several parameters, which are linked to each other. For a rotary impeller, we searched for several parameters, such as its optimal shape, speed in the liquid alloy, and distance from the bottom of the refining ladle, where the aforementioned parameters contribute to the overall wear and life of the rotor and, consequently, of the rotor shaft. The Computational Fluid Dynamics (CFD) method can be used to determine the above-mentioned parameters. This paper describes the particular steps of preparation of rotor geometry for the subsequent setting up of the basic numerical model.

The article deals with the use of computed tomography, an advanced method for evaluating the quality of aluminium castings. Casting quality is a key factor in ensuring safety and reliability in industrial applications. Computed tomography is a comprehensive method allowing a three-dimensional, high-resolution view of the internal structure of materials. The main focus of this paper is the study of BRACKET REAR aluminium castings, manufactured in two-piece moulds using a high-pressure die-casting technology. In this paper, four castings have been analysed which are produced in one cycle. The focus is on the problem of porosity and open stagnation in the castings. A numerical simulation has also been used to illustrate the occurrence of porosity, which can be used to determine both the occurrence of porosity and the occurrence of unfilled volume. The experimental part of the paper describes the methods used to evaluate the BRACKET REAR castings. The numerical simulation was performed in ProCAST 18.0 to determine the occurrence of porosity in the castings under study. The evaluation of computed tomography was performed in myVGL 3.0 2023 software to analyse the internal defects in the castings. The evaluation focused on assessing internal defects and their subsequent effect on the functionality of the final casting.

Both the wear and the geometry of the rotor determine the efficiency of the process of aluminum refining. The paper presents wear tests of two different rotors: I (pump type) and II (propeller type). The operation of both rotors in industrial conditions was compared and their service life was examined. It was found that rotor I is more durable than the tested rotor II, and at the same time it provides a good level of hydrogen removal throughout the operation period, i.e., 1112 refining cycles. Rotor wear after refining was calculated by 3D scanning. The study also investigated the impact of rotor geometry on the efficiency of the refining process. The degassing efficiency was determined during refining in a foundry using the Dichte Index (DI). The alloy density and the volume of hydrogen removed were also tested for five stages of rotor wear: 0%, 25%, 50%, 75% and 100%. Both new rotors performed worse in removing hydrogen from the liquid alloy than the worn rotors due to their humidity which cannot be eliminated in the initial stage of their operation. A Dross Test was also performed to determine non-metallic impurities and compare size and number of cavities for rotor I and II. The best results of removing non-metallic inclusions by flotation were obtained for rotor I at the end of its operation.

Concern for the environment and rational management of resources requires the development of recoverable methods of obtaining metallic materials. This also applies to the production of aluminium and its alloys. The quality requirements of the market drive aluminium producers to use effective refining methods, and one of the most commonly used is blowing an inert gas into liquid aluminium via a rotating impeller. The efficiency and cost of this treatment depends largely on the application of the correct ratios between the basic parameters of the process, which are the flow rate of the inert gas, the speed of the rotor and the duration of the process. Determining these ratios in production conditions is expensive and difficult. This article presents the results of research aimed at determining the optimal ratio of the inert gas flow rate to the rotary impeller speed, using physical modeling techniques for the rotor as used in industrial conditions. The tests were carried out for rotary impeller speeds from 150 to 550 rpm and gas flow rates of 12, 17 and 22 dm³/min. The research was carried out on a 1:1 scale physical model, and the results, in the form of visualization of the degree of gas-bubble dispersion, were assessed on the basis of the five typical dispersion patterns. The removal of oxygen from water was carried out analogously to the process of removing hydrogen from aluminium. The curves of the rate of oxygen removal from the model liquid were determined, showing the course of oxygen reduction during refining with the same inert gas flows and rotor speeds mentioned above.