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The Influence of Selected High – Pressure Die Casting Parameters on the Porosity of EN AB-46000 Alloy Castings

Piątkowski Jarosław, Roskosz Stanisław, Stach Sebastian

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no. 5

361--371

EN

The EN AB-46000 alloy castings are widely used in automotive industry due to their relative good strength combined with a low density and an excellent conductivity. Porosity of EN AB-46000 alloys is one of the most important defects, responsible for the low strength and poor plastic properties of castings as well as their tightness. Quantitative porosity measurement were performed using quantitative metallography and image analysis methods using ImageJ. The study shows that such parameters of high-pressure die casting are the piston speed in the second casting phase and the final pressure increase in the pressing phase. It has been shown that the appropriate selection of these parameters can significantly reduce the porosity of castings made of alloy EN AB-46000.

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Evaluation of Wear Mechanisms of Graphites Used for Crystallisers for Continuous Casting

Brudny Anna, Kulasa Joanna, Juszczyk Barbara, Myalski Jerzy, Roskosz Stanisław, Wycisk R., Kwaśniewski Paweł, Strzępek Paweł, Poręba Marek

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

109--115

EN

This paper presents the results of research concerning the evaluation of tribological properties of graphite materials used, among others, for crystallisers for continuous casting of non-ferrous metals and their alloys. Graphite materials differing not only in their physical properties but also in the technology of their production were selected from a wide range of commercially available products. Wear resistance investigations of the tested graphite materials were carried out on a pin-on-disc tribometer under technically dry friction conditions on a sliding distance of 1000 m. A constant load but variable speed was used in the tests. The mean value of the coefficient of friction and the wear of the material were determined based on the tribological tests carried out. It was observed that as the speed increases, the average value of the coefficient of friction decreases, while the wear increases. A microstructural analysis of the wear track showed that the friction mechanism depends mainly on the graphite formation technology, which is related to the microstructure of the tested materials, and to a lesser extent to their physical and mechanical properties. Varying the speed values made it possible to trace changes in the wear mechanism, on the basis of which it is possible to predict the durability and reliability of graphite crystalliser operation.

3

Evaluation of capabilities of the nanoindentation test in the determination of flow stress characteristics of the matrix material in porous sinters

Madej Lukasz, Legwand Adam, Setty Mohan, Mojzeszko Mateusz, Perzyński Konrad, Roskosz Stanisław, Chrapoński Jacek

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e21, 2022

EN

Herein, we evaluate the nanoindentation test capabilities in the determination of flow stress characteristics of the matrix material in porous sinters. The Distaloy AB sample with 15% porosity after the sintering operation is selected as a case study for the investigation. 2D and 3D imaging techniques are employed first to highlight difficulties in identifying reliable nano hardness measurement zones for further properties evaluation. Then, nanoindentation test results are acquired with Berkovich tip pressed under various loads at different locations in the sample. Systematic indentations in the quartz sample are used as a cleaning procedure to minimize the effect of the possible build-up around the indenter tip. The representative indentation load range is selected based on the extracted material characteristics. With that, the stress–strain response of the sinter matrix material is identified. The reliability of the determined flow stress curve is confirmed with the use of conical nanoindentation measurement results and finite element simulations. Obtained results show that it is possible to calculate reliable flow stress characteristics of the matrix in the porous samples, with the assumption that experiments under various loading conditions and from various locations in the matrix are performed. It is also pointed out that various indentation loads should be used to eliminate the influence of the pile-up or scale effects that affect the overall material response.

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Wybrane zagadnienia doboru materiałów inżynierskich na przykładzie wymienników ciepła

Richter Janusz, Roskosz Stanisław, Ashby Michael F.

Hutnik, Wiadomości Hutnicze

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2020

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Vol. 87, nr 1-2

2-12

PL

W artykule opisano podstawy jednej z najważniejszych metod doboru materiałów opartej na wykresach doboru, tzw. wykresach Ashby’ego i wskaźnikach funkcjonalności. Przykładową procedurę doboru materiałów na wymienniki ciepła przeprowadzono z zastosowaniem programu Cambridge Engineering Selector. Zdefiniowano i przedstawiono wymagania projektowe (cieplne, mechaniczne, korozyjne i ekonomiczne). Wyprowadzono trzy odpowiednie wskaźniki funkcjonalności, które umożliwiły wybór, ocenę i końcowy ranking różnych tworzyw metalowych. Procedurę uzupełniono zaleceniami metodycznymi dotyczącymi doboru materiałów inżynierskich na wymienniki ciepła.

EN

The paper describes the rudiments of one of the most important materials selection methods employing materials selection graphs, so called Ashby’s charts, and performance indices. The example procedure of materials selection for heat exchangers has been performed using Cambridge Engineering Selector software. The design and material requirements (thermal, mechanical, corrosion, economic) have been defined and presented. The relevant three performance indices, enabling selection, assessment and final ranking of various metallic materials, have been developed. The final selection was supplemented with the methodological recommendations concerning the selection procedure of materials for heat exchangers.

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The 2D characterization of pores shape in sintered material before and after deformation

Chrapoński Jacek, Roskosz Stanisław, Madej Łukasz

Inżynieria Materiałowa

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2019

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Vol. 40, nr 4

98--102

EN

The specimens sintered from Distaloy AB iron powder have been examined to evaluate evolution of morphological characteristics under complex deformation conditions. The sintering procedure, in particular, the pressure and the temperature have been adjusted in order to obtain about a 15% porosity level. All examinations were performed on the specimen in as-sintered state, as well as after plastic deformation (compression with cyclic torsion). The volume fraction and pores shape have been described quantitatively before and after deformation. On the basis of statistical analysis, it was found that compression with cyclic torsion with amplitude 3° and frequency 0.5 Hz better reduce porosity than deformation with amplitude 6° and frequency 1 Hz. All shape factors that were used to describe pores geometry, except convexity, differ significantly after plastic deformation in comparison to values before deformation. The Principal Component Analysis of the pores shape factors showed, that it is possible to reduce the characterization of the pores to two principal components. Alternatively, it is sufficient to fully characterize pores shape with three shape factors: circularity, Malinowska’s factor and not correlated with them aspect ratio.

PL

Właściwości materiałów porowatych silnie zależą od cech geometrycznych porów: ich objętości względnej, wielkości, kształtu, rozmieszczenia itp. Odkształcenie plastyczne materiałów porowatych jest procesem, który zmienia ich właściwości, również wskutek zmiany cech porowatości. W trakcie odkształcenia plastycznego morfologia i liczba porów zmienia się, wpływając na właściwości materiału. Kontrola i możliwość kształtowania właściwości materiałów porowatych wymaga wiedzy dotyczącej zmian morfologii porów, przede wszystkim kształtu określanego na podstawie pomiarów na obrazach mikrostruktury zarejestrowanych podczas badań zgładów metalograficznych. Celem pracy było określenie zmian objętości względnej i kształtu porów po ściskaniu z cykliczną rotacją spiekanych próbek oraz dobór współczynników kształtu porów najlepiej charakteryzujących morfologię porów po odkształceniu plastycznym.