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.
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.
The work presents the results of the studies of Co-Cr-Mo casting alloys used in the production of frame casts of removable dentures, crowns and bridges in dental prosthetics. The studies were performed on four Co-Cr-Mo alloys of different contents of Mo, W and other additives. Electrochemical tests were performed, which aimed at examining the corrosion resistance of the alloys and observing the alloy structure after chronoamperometric tests with the potential in the area of the occurrence of the passive layer breakpoint. The alloy microstructure images after chronoamperometric tests show the presence of non-uniformly distributed general corrosion. Moreover, a project of cobalt alloy casting was elaborated using a ceramic mold casting. Additionally, analysis of the obtained microstructure was performed. The microstructure of the examined alloys was of the dendrite type. This microstructure was chemically inhomogeneous and consisted of an austenitic matrix formed by a solid cobalt solution and chromium in the core dendritic structure.
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 investigation results of the kinetics of binding ceramic moulds, in dependence on the solid phase content in the liquid ceramic slurries being 67, 68 and 69% - respectively, made on the basis of the aqueous binding agents Ludox AM and SK. The ultrasonic method was used for assessing the kinetics of strengthening of the multilayer ceramic mould. Due to this method, it is possible to determine the ceramic mould strength at individual stages of its production. Currently self-supporting moulds, which must have the relevant strength during pouring with liquid metal, are mainly produced. A few various factors influence this mould strength. One of them is the ceramic slurry viscosity, which influences a thickness of individual layers deposited on the wax model in the investment casting technology. Depositing of layers causes increasing the total mould thickness. Therefore, it is important to determine the drying time of each deposited layer in order to prevent the mould cracking due to insufficient drying of layers and thus the weakening of the multilayer mould structure.
Variation in final casting dimensions is a major challenge in the investment casting industry. Additional correction operations such as die tool reworking as well as coining operations affect foundry productivity significantly. In this paper influence of basic parameters such as wax material, mould material, number of ceramic coats and feed location on the dimensional accuracy of stainless-steel casting has been investigated. Two levels of each factor were chosen for experimental study. Taguchi approach has been used to design the experiment and to identify the optimal condition of each parameter for reduced dimensional deviation. Analysis of variance has been carried out to determine the contribution of each process parameter. The result reports that selected parameters have significant effect on the dimensional variability of investment casting. Mould material is the dominant parameter with the largest contribution followed by number of ceramic coats and wax material whereas feed location is having negligible contribution.
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.
Precision casting is currently motivated by high demand especially for castings for the aerospace, automotive and gas turbine industries. High demands on precision of this parts pressure foundries to search for the new tools which can help them to improve the production. One of these tools is the numerical simulation of injection process, whereas such software especially for investment casting wax injection, process does not exist yet and for this case must be the existing software, for alloys or plastic, modified. This paper focuses on the use of numerical simulations to predict the behavior of injected models of gas turbine blades segments. The properties of wax mixtures, which were imported into the Cadmould simulation software as a material model, were found. The results of the simulations were verified using the results of 3D scanning measurements of wax models. As a supporting technology for verifying the results was used the Infrared Thermography.