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1
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.
2
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.
3
Content available Prediction of Ferrite Content in Austenitic Cr-Ni Steel Castings During Production
Senberger J., Pernica V., Kana V., Zadera A.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 3
91--94
EN
Determination of the ferrite content in austenitic steels, which solidified under defined conditions. Ferrite content in austenitic matrix was determined from samples with wall thickness of 60 mm. Measured ferrite contents served to propose the regression equations for the calculation of the ferrite content in steels with Cr content of 18 up to 22 % and Ni of 9 up to 11 %. An additional regression equation was proposed for steels with a higher Ni content. The proposed regression equations have been checked up on the operating melts. In conclusion, the ferrite content in the axis of the casting of wall thickness of 500 mm has been calculated and it was compared to the ferrite determined in the usual way from the cast-on test.
4
Content available Influence of compound deoxidation of steel with Al, Zr, rare earth metals, and Ti on properties of heavy castings
Senberger J., Cech J., Zadera A.
Archives of Foundry Engineering
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2012
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Vol. 12, iss. 1
99-104
EN
Heavy steel castings deoxidized with aluminium are sometimes brittle intercrystalline failed during their service along primary grain boundaries what is initiated by aluminium nitrides and so called conchoidal fractures are formed. The tendency to forming the conchoidal fractures depends in particular on cooling rate (the casting modulus), aluminium and nitrogen contents in steel. During deoxidation, when manufacturing heavy castings, the elements with high affinity to nitrogen, zirconium or titanium, are added to steel that would decrease nitrogen activity by the bond on stable nitrides. The formation of stable nitrides should reduce the tendency of steel to the formation of conchoidal fractures. Deoxidation was thermodynamically analyzed at presence of the mentioned elements. For particular conditions a probable course of deoxidation was estimated at test castings. The deoxidation course was checked by microanalysis of deoxidation products (inclusions). For service and experimental castings the anticipated composition of inclusions was compared. It has been proved that in heavy castings with high aluminium contents in steel under studied conditions neither the addition of zirconium nor of titanium nor of rare earth metals will prevent the formation of conchoidal fractures.
5
Content available Increase of liquid metal utilization during production of bearing circle castings for cement furnaces
Zadera A., Senberger J., Carbol Z., Pluhaček J.
Archives of Foundry Engineering
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2012
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Vol. 12, iss. 2
111-116
EN
In manufacture of super heavy castings for cement furnaces a saving of liquid metal has been achieved by lowering the riser weight. By solidification modelling with the aid of the Niyama criterion a zone in the riser was designated where the occurrence of foundry defects (shrinkage porosity) can be expected. A plate of the material of dimensions ca 700*800*250 mm was taken from the riser. After thermal treatment the samples for making the bars for the static tensile test were taken from it. Based on done tests it has been found out that mechanical characteristics obtained from the static tensile test correlate, besides contraction, in the chosen level of statistical importance of p = 0.01 with carbon content. Neither in the zone of probable occurrence of defects designated by the Niyama criterion during solidification modelling the drop of strength characteristics was observed. Carbon content in a decisive extent influenced the strength characteristics. In case of ductility and contraction the convenient correlations with carbon content were observed from the riser height of 200 mm only. In the height of 400 mm there was already considerable variation of values and some values were lower ones than is demanded by standards.
6
Content available Development of a manufacturing technology of compacted graphite iron castings from a cupola furnace
Bouska O., Heunisch J., Zadera A., Nedelova K., Kobersky F.
Archives of Foundry Engineering
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2012
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Vol. 12, iss. 1
125-129
EN
Compacted graphite iron, also known as vermicular cast iron or semiductile cast iron is a modern material, the production of which is increasing globaly. Recently this material has been very often used in automotive industry. This paper reviews some findigs gained during the development of the manufacturing technology of compacted graphite iron under the conditions in Slévárna Heunisch Brno, Ltd. The new technology assumes usage of cupola furnace for melting and is beeing developed for production of castings weighing up to 300 kilograms poured into bentonite sand moulds.
7
Content available remote Solidification of heavy castings
Zadera A., Senberger J., Pluhacek J., Carbol Z.
Archives of Foundry Engineering
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2011
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Vol. 11, iss. 1
109-112
EN
Quality of the casting material is influenced by great numbers of material properties, metallurgical treatment, and particular solidification conditions too. In the case of solidification of heavy castings the properties and quality of the casting material are considerably changed in consequence of running segregation phenomena, worsen metal feeding conditions, and microporosity formation etc. It can even result in defaulting the required strengths and plasticity of the casting material. The work deals with changes of chemical composition and changes of mechanical properties in places with a long solidification time corresponding to them.
8
Content available remote Checking the metallurgy with the aid of inclusion analysis
Senberger J., Zadera A., Cech J.
Archives of Foundry Engineering
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2011
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Vol. 11, iss. 1
118-122
EN
Results of studying the influence of inclusion morphology on properties of heavy casting are given. The inclusion morphology is dependent on content and kind of the deoxidizing element. Due to segregations the inclusions can be formed in heavy castings under different conditions (by concentration of deoxidizing elements) than in castings of common size. In heavy casting during deoxidation the inclusions of the IVth type occur more frequently. Deoxidation with zirconium shows to be for some heavy casting unsuitable one. Similarly in castings deoxidized with cerium and lanthanum the inclusions of greater sizes occur that can unfavourably influence the steel properties and increase the tendency to crack formation. The inclusion morphology after deoxidation with magnesium is also unsuitable for heavy castings.
9
Content available remote Behaviour of oxygen in cast irons
Elbel T., Senberger J., Zadera A., Hampl J.
Archives of Materials Science and Engineering
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2008
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Vol. 33, nr 2
111-116
EN
Purpose: Cast irons are the basic structural material and they form 75% of the world production of castings. The crystallization of cast iron and the formation of graphite are a complex process influencing by oxygen. The aim of our study is to identify the role of oxygen in Fe-C-Si melts. Design/methodology/approach: Continuous comparison of changes in metal composition and oxygen activity during melting, pouring, and solidification of experimental castings, using metallographic methods and microanalysis. Determination of total oxygen content in cast iron by the high temperature extraction method. Findings: Oxygen activity in graphitic cast irons is determined during manufacture of liquid metal and its pouring mainly by carbon and silicon activities. Silicon deoxidates cast irons at lower temperatures, at higher temperatures this function is taken over by carbon. Logarithmic dependences of oxygen activity on temperature for individual graphite forms (lamellar, vermicular, and spheroidal ones) have been obtained. Determination of total oxygen content in cast iron on the other hand gives valuable information for controlling surface and internal quality of cast irons. Practical implications: Possibility of control the cast iron structure and graphitization during crystallization by monitoring the oxygen content with an indirect method of oxygen activity measurement in the melt before metal pouring the mould. Originality/value: The used method gives reproducible results which are comparable under different conditions of metal melting and pouring. Obtained knowledge extends the understanding in the field of cast irons crystallization by less known influence of oxygen.
10
Content available remote State of the art of metal reoxidation study of iron castings
Elbel T., Senberger J., Zadera A., Vladik R.
Archives of Materials Science and Engineering
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2007
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Vol. 28, nr 11
649-652
EN
Purpose: Metal reoxidation causes a number of iron castings defects, particularly when pouring them in greensand moulds. One of them is pinholes the occurrence of which is explained by several hypotheses. One of possible causes is reoxidation processes in the foundry mould cavity. During its flowing in the gating system and in the mould cavity the liquid metal gets into contact with oxygen from air and water vapour. Secondary oxidation of elements takes place in sequence of their affinity to oxygen. Design/methodology/approach: Therefore the authors were aimed at cast irons. Besides indirect methods the reoxidation was researched mainly by direct measurement of oxygen activity during filling of a mould up to solidus temperature. Findings: The use of oxygen activity measurement for direct study of changes caused by reoxidation processes is limited and that it is more suitable for study of the influence of different factors on cast iron crystallization and graphite morphology. Practical implications: Obtained results have confirmed that oxygen activity measurement can serve to the casting quality control. But it is little sensitive for explanation of processes running in a cavity during metal casting. Originality/value: Continuous monitoring of oxygen activity changes in a foundry mould is an original solution since other authors have done their measurements only in a furnace with disposable sensors.
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