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Number of results: 12
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Abstract

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.
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Authors and Affiliations

A. Záděra
V. Kaňa
V. Krutiš
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Abstract

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.
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Authors and Affiliations

A. Záděra
L. Čamek
V. Kaňa
M. Myška
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Abstract

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.
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Authors and Affiliations

A. Záděra
J. Šenberger
V. Pernica
V. Kaňa
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Abstract

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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Authors and Affiliations

A. Záděra
V. Kaňa
V. Pernica
M. Dulava
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Abstract

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.

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Authors and Affiliations

A. Záděra
V. Kaňa
B. Maroš
P. Blažík
J. Čech
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Abstract

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.

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Authors and Affiliations

J. Senberger
J. Cech
A. Zadera
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Abstract

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.

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Authors and Affiliations

V. Kaňa
V. Pernica
A. Zadera
V. Krutiš
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Abstract

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.

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Authors and Affiliations

J. Heunisch
O. Bouska
A. Zadera
K. Nedelova
F. Kobersky
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Abstract

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.
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Bibliography

[1] Xiao, A., Bryden, K.M. (2004). Virtual engineering: A vision of the next-generation product realization using virtual reality technologies. Proceedings of the ASME 2004 Design Engineering Technical Conferences – DETC’04, 28 September – 2 October, pp 1-9.Salt Lake City, Utah, #57698.
[2] Pekkola, S. & Jäkälä, M. (2007) From technology engineering to social engineering: 15 years of research on virtual worlds. The DATA BASE for Advances in Information Systems. 38(4), 11-16.
[3] Bao, Jin, J.S., Gu, Y., Yan, M.Q. & Ma, J.Q. (2002). Immersive virtual product development. Journal of Materials Processing Technology. 129(1-3), 592-596. DOI: 10.1016/S0924-0136(02)00655-6.
[4] Van der Auweraer, H. (2010). Virtual engineering at work: The challenges for designing intelligent products. In: Proceedings of the TMCE 2010 Symposium, April 12-16, (pp. 3-18), Ancona, Italy.
[5] Stawowy, A., Wrona, R., Brzeziński, M. & Ziółkowski, E. (2013). Virtual factory as a method of foundry design and production management. Archives of Foundry Engineering. 13(1), 113-118. DOI: 10.2478/afe-2013-0022
[6] Dépincé, P., Chablat, D., Woelk, P.O. (2004) Virtual manufacturing: tools for improving design and production, Dans International Design Seminar - CIRP International Design Seminar, Egypt.
[7] Kumar, P., Ahuja, I.P.S. & Singh, R. (2013). Framework for developing a hybrid investment casting process. Asian Review of Mechanical Engineering, 2(2), 49-55.
[8] Kügelgen, M. (2008). From 7 days to 7 hours – Investment casting parts within the shortest time, 68th WFC - World Foundry Congress, 7th - 10th February, 2008, (pp. 147-151).

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Authors and Affiliations

V. Krutiš
1
ORCID: ORCID
P. Šprta
1
V. Kaňa
1
ORCID: ORCID
A. Zadera
1
J. Cileček
2

  1. Brno University of Technology, Czech Republic
  2. Alucast s.r.o., Czech Republic
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Abstract

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.

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Authors and Affiliations

V. Kaňa
ORCID: ORCID
V. Krutiš
ORCID: ORCID
P. Bořil
ORCID: ORCID
A. Záděra
M. Rimko
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Abstract

This work deals with the problem of intermetallic phases in cast standard duplex steel ASTM A890 Gr 4A (generally known as 2205). The investigated steel was subjected to isothermal heat treatment in the range from 595 °C to 900 °C and in the duration from 15 minutes to 245 hours, and was also investigated in terms of anisothermal (natural) cooling after casting into the mould. The precipitation starts at grain boundaries with a consistent ferrite transformation. The work is focused on the precipitation of the sigma phase (σ) and the chi phase (χ). Examination of the microstructure was conducted using light and scanning electron microscopy. Their statistical analysis was carried out using the results of the investigations of precipitation processes in the microstructure, both within the grains and at the grain boundaries. To illustrate this impact, the surface area of precipitates was evaluated. The percentage of these intermetallic phases was calculated by measuring their area using a computer image analysis system. Based on their observations, a combined time-temperature transformation (TTT) diagram with continuous cooling transformation (CCT) curves was created.
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Authors and Affiliations

M. Myška
1
ORCID: ORCID
P. Bořil
1
ORCID: ORCID
V. Krutiš
1
ORCID: ORCID
V. Kaňa
1
ORCID: ORCID
A. Zádĕra
1
ORCID: ORCID

  1. Brno University of Technology, Czech Republic

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