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1
Content available Study of the Properties of the AlSi9Cu3 Alloy Depending on the Ratio of Returnable Material in the Batch
Matejka M., Bolibruchová D., Chalupová M.
Archives of Metallurgy and Materials
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2021
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Vol. 66, iss. 1
15--23
EN
Recycling of aluminium returnable material through its reuse is now an essential component of the production of aluminium alloy castings. The main goal is to find a suitable ratio of the primary alloy and the returnable material in the batch, thus determining the right compromise between the price and the quality of the casting. Experimental alloys were evaluated by thermal analysis, combination of structural analytical techniques and selected mechanical properties. The alloys were also subjected to tearing susceptibility testing. The increase in the returnable material amount resulted in changes in the alloy properties at the first increase in volume to 20%. After exceeding the balanced ratio (50:50), there was considerable degradation of the microstructure, failure to achieve the minimum values of some mechanical properties required by the standard, and the alloy showed increased susceptibility to tearing.
2
Content available Modification of Constrained Rod Casting Mold for New Hot Tearing Measurement
Malau V., Akhyar H., Iswanto P. T.
Archives of Metallurgy and Materials
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2018
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Vol. 63, iss. 3
1201--1208
EN
Hot tearing severity was evaluated in this experiment by introducing a new apparatus called Constrained Rod Casting Modified Horizontal (CRCM-Horizontal). Six constraint bars with different lengths can produce hot tearing on the cast sample. Mold position was modified from vertical to horizontal and the shape was changed from a harp shape to a star shape, which allows for the liquid metal to feed into each rod cavity simultaneously. Hot tearing development was recorded along the bars by a digital camera. A new Hot Tearing Susceptibility ( HTS) formula was developed for quantitative investigation of hot tearing on a cast sample. The parameters of the HTS formula are bar length of cast sample (Li), tear severity (Ci) and location of hot tear (Pi). Footprint charts and hot tear scales are used to illustrate hot tearing severity. The experiment was conducted with Al-1.36Zn-1.19Si and Al-5.9Cu-1.9Mg alloys to investigate the sensibility of the apparatus and modification its operation.
3
Content available Effect of Strontium Inoculation on Hot Tearing in Aluminium Alloys
Bolibruchová D., Bruna M., Pastirčák R., Major-Gabryś K.
Archives of Metallurgy and Materials
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2018
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Vol. 63, iss. 4
1837--1842
EN
Main aim of submitted work is evaluation and experimental verification of inoculation effect on Al alloys hot-tear sensitivity. Submitted work consists of two parts. The first part introduces the reader to the hot tearing in general and provides theoretical analysis of hot tearing phenomenon. The second part describes strontium effect on hot tearing susceptibility, and gives the results on hot tearing for various aluminium alloys. During the test, the effect of alloy chemical composition on hot tearing susceptibility was also analyzed. Two different Al-based alloys were examined. Conclusions deals with effect of strontium on hot tearing susceptibility and confirms that main objective was achieved.
4
Content available Development of hot tearing evaluation method for Al-based alloys
Brůna M.
Archives of Metallurgy and Materials
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2017
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Vol. 62, iss. 1
345--349
EN
This paper focuses on developing an advanced test method and its use to study hot tearing defects in aluminium alloy castings. The paper consists of two parts. The first part introduces the reader to hot tearing in general, and provides theoretical analysis of the hot tearing phenomenon. The second part describes a newly developed method for assessing hot tearing susceptibility, and also gives the results on hot tearing for various aluminium alloys. During the test, the effect of alloy chemical composition on hot tearing susceptibility was analyzed. Three different Al-based alloys with varying Si, Cu and Ti contents were examined. Conclusions deal with the effect of individual elements on hot tearing susceptibility, and confirm that the main objective was achieved and the proposed method proves to be repeatable and reliable.
5
Content available Observation of Hot Tearing in Sr-B Modified A356 Alloy
Uludağ M., Çetin R., Dışpınar D.
Archives of Foundry Engineering
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2017
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Vol. 17, iss. 4
165--168
EN
In this work, T-shaped mould design was used to generate hot spot and the effect of Sr and B on the hot tearing susceptibility of A356 was investigated. The die temperature was kept at 250ºC and the pouring was carried out at 740ºC. The amonut of Sr and B additions were 30 and 10 ppm, respectively. One of the most important defects that may exist in cast aluminium is the presence of bifilms. Bifilms can form by the surface turbulence of liquid metal. During such an action, two unbonded surfaces of oxides fold over each other which act as a crack. Therefore, this defect cause many problems in the cast part. In this work, it was found that bifilms have significant effect over the hot tearing of A356 alloy. When the alloy solidifies directionally, the structure consists of elongated dendritic structure. In the absence of equiaxed dendrites, the growing tips of the dendrites pushed the bifilms to open up and unravel. Thus, leading to enlarged surface of oxide to become more harmful. In this case, it was found that these bifilms initiate hot tearing.
6
Content available High temperature brittleness of cast alloys
Telejko I., Adrian H., Guzik B.
Archives of Metallurgy and Materials
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2013
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Vol. 58, iss. 1
83-87
EN
Over-all mechanical properties of alloys are extremely low at the last stage of solidification where alloy exists at brittle temperature range (BTR). When the solidification process is completed a sudden and marked change in strength and ductility of metal is observed. It means that as long as liquid phase is present, metal will fail in a brittle manner. There are known different theories of brittleness of alloys in existence of liquid phase. The idea involved by authors of the paper is as follows: three major factors caused by presence of liquid may be taken into account: - decreasing the energy needed for crack nucleation, - increasing atomic diffusional flux out of the crack tip, - creating a path for abnormally quick diffusion of atoms from the crack tip.
PL
Własności mechaniczne stopów są bardzo niskie w ostatnim stadium krzepnięcia, w którym stop wykazuje kruchość wysokotemperaturową. Przy końcu procesu krzepnięcia obserwuje się nagłą zmianę wytrzymałości i plastyczności metalu. Dopóki występuje faza ciekła metal ulega zniszczeniu w sposób kruchy. Przyczyna tego mogą być trzy główne czynniki związane z obecnością fazy ciekłej: a) spadek energii potrzebnej do zarodkowania pęknięcia, b) wzrost strumienia dyfuzji atomów od wierzchołka pękniecia, c) utworzenie ścieżki do anomalnie szybkiej dyfuzji atomów od wierzchołka pękniecia.
7
Content available A New Stress Criterion for Hot-Tearing Evaluation in Solidifying Casting
Szczygiol N.
Acta Mechanica et Automatica
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2012
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Vol. 6, no. 4
56-62
EN
This work concerns a new criterion for hot-tearing evaluation in castings. Algorithm describing the conduction of computer simulations of phenomena accompanying the casting formation, which performing is the preparation stage for using of this criterion, is also described. According to the low recurrence of phenomena occurring during solidification (e.g. grained structure parameters, stresses distribution) the casting’s hot-tearing inclination can be estimated only in approximated manner. Because of still following at present rapid computer processors development, and techniques of its programming, enables to suppose that in short time the efficiency of computer simulations will arise so much, the problem of hot-tearing evaluation newly became interesting for the team working on computer simulations at the Institute for Computer and Information Sciences at Częstochowa University of Technology.
8
Content available remote Numeryczna ocena skłonności do pękania odlewów o strukturze równoosiowej
Szwarc G., Sczygiol N.
Archiwum Odlewnictwa
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2004
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R. 4, nr 14
526-531
PL
W pracy przedstawiono lokalny współczynnik skłonności do pękania na gorąco odlewów o równoosiowej strukturze wewnętrznej. Do wyznaczenia tego współczynnika niezbędna jest znajomość stanu naprężenia odlewu w czasie gdy znajduje się on w stanie dwufazowym (mieszanina stało-ciekła). W pracy zaprezentowano metodykę wyznaczania tego stanu naprężenia z uwzględnieniem zmian kinetyki krzepnięcia na poziomie ziaren struktury wewnętrznej odlewu (skala mikro). Do obliczeń numerycznych wykorzystano metodę elementów skończonych.
EN
In this paper a local coefficient of tendency of casts with equiaxial structure to hot tearing is presented. In order to compute this coefficient knowledge about stress state in the cast at the moment when it is semi-solid is needed. Methodology of its calculation, taking change of solidification kinetics at the level of grains of internal structure of the cast (micro-scale) into account, is described. The finite element method is used for numerical computations.
9
Content available remote Wysokotemperaturowy zakres kruchości staliwa
Telejko I.
Archiwum Odlewnictwa
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2003
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R. 3, nr 10
261--266
PL
Zakres temperatur kruchości jest tożsamy z zakresem pękania na gorąco odlewanej, a także spawanej stali. Szerokość tego zakresu dla tego samego gatunku staliwa zależy przede wszystkim od jego niższej temperatury - rzeczywistej temperatury solidus – która może się wahać od odczytanej z układu równowagi Fe-C, (segregacja składników ograniczona do węgla, manganu i krzemu) do określonej dla staliwa zawierającego silnie segregującą domieszkę o bardzo małej rozpuszczalności w fazie stałej. We wszystkich gatunkach staliwa węglowego i niskostopowego domieszką taką jest siarka, w staliwie Hadfielda – fosfor. W wyniku dodatku pierwiastka zapobiegającemu wzrostowi przed frontem krzepnięcia stężenia siarki możliwe jest podwyższenie rzeczywistej temperatury solidus staliwa nawet do wartości bliskiej równowagowej. Efektem jest znaczne ograniczenie pękania stali przy jej odlewaniu i spawaniu.
EN
Cracking susceptibility of alloys depends mainly on the brittleness solidification range BTR. As the process of microsegregation of elements of steel is negligible during the early period of solidification, the upper limit of BTR changes mainly with the change in carbon content. The transition from brittle state to ductile appears when the liquid phase disappears from the grain boundaries. Under the conditions of non-segregation, the brittle-ductile transition temperature (the end of BTR) is very close to solidus calculated from an Fe-C diagram. Under segregate conditions (a real condition of solidification of industrial steel) the composition of liquid during the final period of solidification is closed to Fe-C-S. The brittle-ductile transition temperature is equal to the solidification temperature of the sulphides.
10
Content available remote Próby technologiczne w badaniu procesu tworzenia się pęknięć na gorąco w odlewach staliwnych
Telejko I., Chojecki A.
Archiwum Odlewnictwa
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2001
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R. 1, nr 2
571--576
PL
Analizowano przydatność prób technologicznych i specjalnych, dla oceny skłonności staliwa do tworzenia pęknięć w zakresie krzepnięcia. Stwierdzono, że uzyskane za pomocą tych prób wyniki wykazują znaczne różnice, a niekiedy są wręcz przeciwstawne. Rzeczywistą odporność stopu na pękanie można ocenić jedynie na podstawie pomiaru właściwości mechanicznych w tym zakresie, w którym tworzą się pęknięcia. Takie badania dostarczają danych dla oceny prawdopodobieństwa pękania konkretnych odlewów.
EN
Usefulness of the technological tests in the examination of hot tearing tendency of cast steel has been studied. It was found that the large scattering of results appears in such tests. The study of mechanical properties of an alloy in the brittle temperature range can furnish a proper information about the probability of hot tears nucleation and propagation.
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