Browsing by Subject "forma ceramiczna"

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Access status: Open Access ,
Dependence of tensile wet strength from regeneration time and grain size of the matrix ceramic moulds
(2011) Kamińska, Jadwiga; Kolczyk, Joanna; Żymankowska-Kumon, Sylwia
Production technology of nwestment casting involves transmitting the elements of shape, dimensions and properties by filling in the appropriate liquid metal ceramic forms reproduced by a model made of wax removed by melting it. The manufacturing process of inwestment casting in the lost wax technology consists of a number of technological operations: preparing of wax models and their assembling in the model units, the preparation of ceramic mixture, successive layers of debris, wax melting in an autoclave, drying the samples at 100 °C, heating the samples at temperatures ranging from 400 to 700 °C. So far, the technology was based on the use of ceramic mixture, which the bond was hydrolysed ethyl silicate. Currently, due to environmental protection and improvement of working conditions, more and more binders with alcohol is replaced with an aqueous solution of colloidal silica. In the study, to create the individual layers a ceramic form, used regenerated ceramic mixture derived from foundry and green ingredients. The regeneration time was respectively 5 and 15 minutes. Used ceramic moulds after mechanical reclamation was given to sieve analysis to determine the grain size (di). Grain sizes 0.2, 0.4 and 0.63 mm were used for the coating of ceramic moulds. The paper presents results of research aimed at the determination of the relationship between tensile wet strength and grain size of ceramic mould: Rm = f[dL). Tests were conducted on cylindrical samples, which deposited the layers of reclaimed ceramic material.
Access status: Open Access ,
Drying and hardening of ceramic moulds applied in the investment casting technology - investigations of the process kinetics
(2011) Zych, Jerzy; Snopkiewicz, Tomasz
Ceramic moulds applied in the investment casting technology are multilayer structures, built in an alternating process of depositing and drying of successive layers. Each individual layer is formed from a fluid (liquid) ceramic moulding sand and a grain matrix. In the current, environmentally technology fluid ceramic sands based on ethyl silicate are being substituted by ceramic sands containing colloidal silica as a binder. The ability and rates of drying and hardening of these new colloidal (water) ceramic moulding sands are quite different than of the ones which have a binder dissolved in alcohol. The kinetics of the process based on new binders is not well known. The technological principle requires that the successive layer deposition is done only when the one deposited previously is already sufficiently dry. Investigations of the possibility of application of some methods including: ultrasound, resistance and weigh method are presented in the paper. Advantages and disadvantages of each method are indicated as well as the assessment of their practical suitability is perfomed.
Access status: Open Access ,
Effect of grain size of the reclaimed matrix ceramic moulds used in the lost wax technology on the strength at high temperature
(Wydawnictwa AGH, 2010) Kamińska, Jadwiga; Kolczyk, Joanna; Żymankowska-Kumon, Sylwia
Production technology of investment casting involves transmitting the elements of shape, dimensions and properties by filling in the appropriate liquid metal ceramic forms reproduced by a model made of wax removed by melting it. The manufacturing process of investment casting in the 8 lost wax technology consists of a number of technological operations: preparing of wax models and their assembling in the model units, the preparation of ceramic mixture, successive layers of debris, wax melting in an autoclave, drying the samples at 100 °C, heating the samples at temperatures ranging from 400 to 700 °C. So far, the technology was based on the use of ceramic mixture, which the bond was hydrolysed ethyl silicate. Currently, due to environmental protection and improvement of working conditions, more and more binders with alcohol is replaced with an aqueous solution of colloidal silica. In the study, as the basic of individual layers a ceramic form, used regenerated ceramic mixture derived from foundry and green ingredients. Used ceramic moulds after mechanical reclamation was given to sieve analysis to determine the grain size $(d_{L})$. Grain sizes 0.2, 0.4 and 0.63 mm were used for the coating of ceramic moulds. The paper presents results of research aimed at the determination of the relationship between tensile wet strength and grain size of ceramic mould: $R_{m} = f(d_{L})$. Tests were conducted on cylindrical samples, which deposited a layer of reclaimed ceramic material.
Access status: Open Access ,
Przyczyny powstawania niedolewów w supercienkościennych elementach odlewanych z nadstopów na osnowie niklu
(2010-07-09) (Data obrony: 2010) Cygan, Rafał
Wydział Odlewnictwa
The research described in this doctoral thesis is a result of a wider project aimed at the description of physical and chemical phenomena occurring at the metal – ceramic mold and ceramic mold – environment boundary during the casting and solidification of investment castings (Research and development project R15 008 03 realized by the AGH in Cracow 2007 – 2010). The physical and chemical phenomena occurring at the metal-ceramic mold interface during the pouring of liquid metal into the mold influence the casting process significantly, and can constitute one of the main reasons for the forming of defects, including misruns and nonfills. In order to efficiently model and, as a result, optimize those technological processes, a series of experiments aimed at the investigation of metal-mold interface phenomena was conducted. The phenomenon of wetting of ceramic materials by liquid metals plays a major role in technological processes involving ceramics and liquid phase. The characteristic used most often to describe the degree of ceramic wetting by a liquid metal is the wetting angle $\theta$. The thermal and physical properties of shelling (molding) materials have a decisive influence on the structure and properties of a casting. That is so because they have the decisive influence on the thermal exchange processes between the casting and the ceramic mold. The exact importance of such properties can be especially appreciated when performing computer simulations of the casting solidification and cooling processes. The solidification process creates the original, primary structure, and the cooling of an already solidified casting creates the final structure of the casting alloy. The course of these processes, which decides about the obtained structure and properties of the casting, is largely dependant on the rate, at which the heat is being removed from the solidifying alloy. Very complicated geometries (super-thin sectioned castings with turbine blade sections measuring at times as little as 0,2 mm), less than perfect casting properties of superalloys and very strict quality standards contribute to the fact, that scrap rates for such castings can be very high. The purpose of a comparison between computer simulations and real-life experiments was to define the preliminary basic physical and chemical parameters, such as the thermal conductivity coefficient between the ceramic mold and insulation or between the ceramic mold and the environment; as well as to perform an initial verification of the ProCast simulation suite ceramic and thermally insulating materials database.