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1
Content available Corrosion Resistance of Cast Duplex Steels
Müller Peter, Pernica V., Kaňa V.
Archives of Foundry Engineering
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2022
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Vol. 22, iss. 3
5--10
EN
The aim of this work is to investigate the resistance of cast duplex (austenitic-ferritic) steels to pitting corrosion with respect to the value of PREN (Pitting Resistance Equivalent Number). Pitting corrosion is one of the most common types of corrosion of stainless steels. In most cases, it is caused by the penetration of aggressive anions through the protective passive layer of the steel, and after its disruption, it leads to subsurface propagation of corrosion. The motivation for the research was a severe pitting corrosion attack on the blades of the gypsum-calcium water mixer in a thermal power plant operation. In order to examine the corrosion resistance, 4 samples of 1.4517 steel with different concentrations of alloying elements (within the interval indicated by the steel grade) and thus with a different PREN value were cast. The corrosion resistance of the samples was evaluated by the ASTM G48 – 11 corrosion test in a 6% aqueous FeCl3 solution at room and elevated solution temperatures. To verify the possible effect of different alloying element concentrations on the mechanical properties, the research was supplemented by tensile and Charpy impact tests. Based on the results, it was found that a significant factor in the resistance of duplex steels to pitting corrosion is the temperature of the solution. For the components in operation, it is therefore necessary to take this effect into account and thoroughly control and manage the temperature of the environment in which the components operate.
2
Content available Influence of Heat Treatment and Nickel Content on the Properties of the GX4CrNi13-4 Steel
Kaňa V., Krutiš V., Bořil P., Záděra A., Rimko M.
Archives of Metallurgy and Materials
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2021
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Vol. 66, iss. 1
37--41
EN
For the EN GX4CrNi13-4 martensitic stainless steel, research was conducted to investigate the impact of the quenching intensity and the content of nickel on the mechanical properties and amount of retained austenite. It was found that the amount of retained austenite significantly increases with growing nickel concentration. On the other hand, the cooling rate at quenching makes a difference only if the cooling is intensive, then amount of retained austenite decrease. A higher nickel content improves the mechanical properties. With more intensive cooling, the tensile strength decreases while the yield strength increases. The ductility is not significantly affected by the cooling intensity.
3
Content available Integration of Virtual Engineering and Additive Manufacturing for Rapid Prototyping of Precision Castings
Krutiš V., Šprta P., Kaňa V., Zadera A., Cileček J.
Archives of Foundry Engineering
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2021
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Vol. 21, iss. 1
51--55
EN
The present paper is concerned with the practical interconnection between virtual engineering tools and additive model manufacturing technologies and the subsequent production of a ceramic shell by rapid prototyping with the use of Cyclone technology to produce the aluminium casting prototype. Prototypes were developed as part of the student formula project, where several parts originally produced by machining were replaced by castings. The techniques of topological optimization and the combination with the tools of the numerical simulation were used to optimise the virtual prototype before a real production of the first prototype. 3D printing of wax pattern ensured direct and fast assembly of the cluster without any additional operations and troubles during dewaxing. The shell was manufactured in 6 hours thanks to a system of quick-drying of individual layers of ceramic shell. It has been verified that the right combination of individual virtual tools with the rapid prototyping can shorten the development time and delivery of the first prototypes from a few months to a few weeks.
4
Content available Comparison of Methods for Determining the Ferrite Content in Duplex Cast Steels
Kaňa V., Pernica V., Zadera A., Krutiš V.
Archives of Foundry Engineering
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2019
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iss. 2
85--90
EN
The paper is concerned with comparing the methods for determining the ferrite content in castings from duplex stainless steels. It uses Schaeffler diagram, empirical formula based calculation, image analysis of metallographic sample, X-ray diffraction and measurement with a feritscope. The influence of wall thickness of the casting on the ferrite content was tested too. The results of the experiments show that the casting thickness of 25 or 60 mm does not have a significant effect on the measured amount of ferrite. The image analysis of metallographic sample and the measurement with the feritscope appear to be the most suitable methods. On the contrary, predictive methods, such as Schaeffler diagram or empirical formula based calculation are only indicative and cannot replace the real measurements. X-ray diffraction seems to be the least suitable measuring method. Values of ferrite content measured in such a way often deviated from the values measured by image analysis and with feritscope.
5
Content available Properties of Type SiMo Ductile Irons at High Temperatures
Roučka J., Abramová E., Kaňa V.
Archives of Metallurgy and Materials
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2018
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Vol. 63, iss. 2
601--607
EN
Ductile irons of the type of Si-Mo are characterized by increased resistance to long-term influence of high temperatures and cyclic temperature changes. They are mainly used in castings of combustion engine exhaust piping and other castings utilized at temperatures of up to 850°C. The aim of the study is to verify the mechanical properties of non-alloyed cast iron EN CSN GJS 450, SiMo4-0.5 and SiMo5-1 ductile irons at temperatures of 700 to 800°C, and the extent of their superficial oxidation after longterm annealing at a temperature of 900°C. Via chemical microanalysis the composition of oxidation products in the surface layer was evaluated.
6
Content available Effect of Alloying Elements on Properties and Structure of High Chromium Cast Irons
Kaňa V., Záděra A., Krutiš V.
Archives of Metallurgy and Materials
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2018
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Vol. 63, iss. 2
609--614
EN
The paper deals with hypereutectic high chromium cast irons. The subject of examination was the effect of various alloying elements (Ti, W, Mo, V) on the size of primary carbides and on the resultant material hardness. Using a scanning electron microscope with a wave dispersion analyser, the carbon content in carbides was established. To determine the other elements, an energy dispersion analyser was used. It was found that both the primary and the eutectic carbides were of the M7C3 type and very similar in composition. The carbides always contained Cr and Fe, and also W, Mo, V or Ti, in dependence on the alloying elements used. The structure of materials containing only chromium without any alloying additions exhibited coarse acicular primary carbides. The structure of materials alloyed with another element was always finer. Marked refinement was obtained by Ti alloying.
7
Content available Prediction of the Mechanical Properties of Chrome-Nickel Austenitic Stainless Steels with Respect to their Chemical Composition
Záděra A., Maroš B., Blažík P., Čech J., Kaňa V.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 1
217--221
EN
The research was concerned with the influence of chemical composition of austenitic steels on their mechanical properties. Resulting properties of castings from austenitic steels are significantly influenced by the solidification time that affects the size of the primary grain as well as the layout of elements within the dendrite and its parts with regard to the last solidification points in the interdendritic melt. During solidification an intensive segregation of all admixtures occurs in the melt, which causes a whole range of serious metallurgical defects and it has also a significant influence on subsequent precipitation of carbides and intermetallic phases. Chemical heterogeneity then affects the structure and mechanical properties of the casting. In a planned experiment, we cast melted steels containing 18 to 28 % Cr and 8 to 28 % Ni with variable carbon and nitrogen contents. Testing the tensile strength of the cast specimens we could determine the Rp0.2, Rm, and A5 values. The dependence of the mechanical properties on the chemical content was described by regression equations. The planned experiment results allow us to control the chemical content for the given austenitic steel quality to achieve the required values of the mechanical properties.
8
Content available Influence of Heat Treatments and Ni Content on Properties of Martensitic Stainless Steel
Čamek L., Kaňa V., Záděra A., Myška M.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 2
220--225
EN
The article deals with the influence of chemical composition of martensitic stainless steel for castings GXCrNi13-4 (the 1.4317 material) on mechanical properties and structure of as cast steel after heat treatment. Properties of these martensitic stainless steel are heavily influenced by chemical composition and structure of the material after heat treatment. Structure of these steels after quenching is formed with martensite and residual austenite. When tempering the steel the carbon content in martensite is reduced and gently deposited carbides occur. The way of heat treatment has a major impact on structure of martensitic steels with low carbon content and thus on strength, hardness and elongation to fracture of these steels. Chemical composition of the melt has been treated to the desired composition of the lower, middle and upper bounds of the nickel content in the steel within the limits allowed by the standard. Test blocks were gradually cast from the melt. The influence of the nickel equivalent value on structure and properties of the 1.4317 steel was determined from results of mechanical tests.
9
Content available Oxygen Activity in Melts of Fe-C-Cr-Ni Based Alloys
Záděra A., Dulava M., Pernica V., Kaňa V.
Archives of Foundry Engineering
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2016
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Vol. 16, iss. 4
181--186
EN
Oxygen is an element that is first purposely brought into the steel melt to remove some unwanted elements or to reduce their concentration (oxidation). In the made cast steel there is on the contrary necessary to reduce the oxygen content with the use of deoxidation to such a level in order to avoid a reaction with carbon with the formation of CO bubbles. Concentration of oxygen in steel before casting is given, in particular, by the manner of metallurgical processing and the used deoxidation process. Oxygen is found in molten steels both as chemically bound in the form of oxides and in the form of oxygen dissolved in the solution – the melt. Chemical composition of the melt strongly influences the activity of oxygen dissolved in the melt and further on the composition of oxidic inclusions forming in the melt during the reaction with oxygen. In the Fe-C-Cr-Ni based alloys in the reaction with oxygen greatly participates also chrome, whose products are often in solid state and they are the cause of forming such defects as e.g. oxidic films.
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