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Artificial Intelligence Approaches to Determine Graphite Nodularity in Ductile Iron

Brait Maximilian, Koppensteiner Eduard, Schindelbacher Gerhard, Li Jiehua, Schumacher Peter

Journal of Casting & Materials Engineering

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2021

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Vol. 5, no. 4

94--102

EN

The complex metallurgical interrelationships in the production of ductile cast iron can lead to enormous diﬀerences in graphite formation and local microstructure by small variations during production. Artiﬁcial intelligence algorithms were used to describe graphite formation, which is inﬂuenced by a variety of metallurgical parameters. Moreover, complex physical relationships in the formation of graphite morphology are also controlled by boundary conditions of processing, the eﬀect of which can hardly be assessed in everyday foundry operations. The inﬂuence of relevant input parameters can be predetermined using artiﬁcial intelligence based on conditions and patterns that occur simultaneously. By predicting the local graphite formation, measures to stabilise production were deﬁned and thereby the accuracy of structure simulations improved. In course of this work, the most important dominating variables, from initial charging to ﬁnal casting, were compiled and analysed with the help of statistical regression methods to predict the nodularity of graphite spheres. We compared the accuracy of the prediction by using Linear Regression, Gaussian Process Regression, Regression Trees, Boosted Trees, Support Vector Machines, Shallow Neural Networks and Deep Neural Networks. As input parameters we used 45 characteristics of the production process consisting of the basic information including the composition of the charge, the overheating time, the type of melting vessel, the type of the inoculant, the fading, and the solidification time. Additionally, the data of several thermal analysis, oxygen activity measurements and the final chemical analysis were included. Initial programme designs using machine learning algorithms based on neural networks achieved encouraging results. To improve the degree of accuracy, this algorithm was subsequently adapted and reﬁned for the nodularity of graphite.

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Initial Assessment of Graphite Precipitates in Vermicular Cast Iron in the As-Cast State and after Thermal Treatments

Soiński M. S., Jakubus Aneta, Borowiecki B., Mierzwa P.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 4

131--136

EN

The purpose of the work was to determine the morphology of graphite that occurs in vermicular cast iron, both in the as-cast state and after heat treatment including austenitization (held at a temperature of 890°C or 960°C for 90 or 150 min) and isothermal quenching (i.e. austempering, at a temperature of 290°C or 390°C for 90 or 150 min). In this case, the aim here was to investigate whether the heat treatment performed, in addition to the undisputed influence of the cast iron matrix on the formation of austenite and ferrite, also affects the morphology of the vermicular graphite precipitates and to what extent. The investigations were carried out for the specimens cut from test coupons cast in the shape of an inverted U letter (type IIb according to the applicable standard); they were taken from the 25mm thick walls of their test parts. The morphology of graphite precipitates in cast iron was investigated using a Metaplan 2 metallographic microscope and a Quantimet 570 Color image analyzer. The shape factor F was calculated as the quotient of the area of given graphite precipitation and the square of its perimeter. The degree of vermicularization of graphite was determined as the ratio of the sum of the graphite surface and precipitates with F <0.05 to the total area occupied by all the precipitations of the graphite surface. The examinations performed revealed that all the heat-treated samples made of vermicular graphite exhibited the lower degree of vermicularization of the graphite compared to the corresponding samples in the as-cast state (the structure contains a greater fraction of the nodular or nearly nodular precipitates). Heat treatment also caused a reduction in the average size of graphite precipitates, which was about 225μm2 for the as-cast state, and dropped to approximately 170-200 μm2 after the austenitization and austempering processes.

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Influence of Structure on the Thermophisical Properties of Thin Walled Castings

Górny M., Lelito J., Kawalec M., Sikora G.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 2 spec.

23--26

EN

This study addresses the effect of the cooling rate and of titanium additions on the thermophysical parameters of thin-walled compacted graphite iron (TWCGI) castings. Various molding materials were used (silica sand and insulating sand LDASC- Low-Density Alumina-Silicate Ceramic) to achieve different cooling rates. Different titanium additions were caused by various amount of Ferro Titanium. The research work was conducted for thin-walled iron castings with a 3-mm wall thickness. The tested material represents the occurrence of graphite in the shape of flakes (C and D types, according to the ISO Standard), nodules or compacted graphite with a percent of nodularity and different shape factor. Thermal conductivity has been determined by the laser flash technique in a temperature range of 22-600°C. The results show that the cooling rates together with the titanium content largely influence the graphite morphology and finally thermal conductivity of thin walled iron castings.

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Influence of electromagnetic field parameters on the morphology of graphite in grey cast iron

Szajnar J., Stawarz M., Wróbel T., Sebzda W.

Archives of Foundry Engineering

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2009

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Vol. 9, iss. 1

181-184

EN

One way to improve the unification of the casting structure may be the application of forced convection of liquid metal during the crystallization in the form or continuous casting mould. This paper presents the results describing the influence of selected parameters of rotating electromagnetic field enforcing the movement of liquid metal in the form on the morphology of graphite in grey cast iron. The results were fragmented graphite flakes in conditions of regulating the rate of cooling in the range of temperature [...] and casting with the influence of electromagnetic field.

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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.

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The influence of external factors on morphology of graphite in grey cast iron

Szajnar J., Stawarz M., Wróbel T.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 3s

159--162

EN

One of the methods, which improved unification of structure may be application of forced movement in time of metal crystallization. In studies to generating of forced movement of liquid metal was applied electromagnetic filed. In aim of determination of electromagnetic field influence on morphology of graphite was made a comparison between microstructure of cast iron ingots, which were poured in conventional conditions and with action of electromagnetic field. The results of studies show improvement in graphite morpholgy on condition that suitably slow process of casting solidification.

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Wpływ pola magnetycznego na morfologię grafitu w żeliwie szarym

Stawarz M., Szajnar J.

Archiwum Odlewnictwa

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2006

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R. 6, nr 22

461-466

PL

Jednym ze sposobów poprawy jednorodności struktury odlewów może być zastosowanie podczas krystalizacji wymuszonej konwekcji. W przeprowadzonych badaniach do wytwarzania wymuszonego ruchu ciekłego metalu w formie zastosowano pole magnetyczne. W tym celu porównano morfologię grafitu we wlewkach wytworzonych tradycyjnie oraz pod wpływem pola elektromagnetycznego. Wirujące pole elektromagnetyczne pozwala na poprawienie morfologii grafitu.

EN

One of the ways to improve structural homogeneity is application of forced convection during solidification of the casting. In presented studies forced convection was obtained by use of electromagnetic field. The graphite morphology of gray cast iron under electromagnetic rotating field was studied. In the studies alloy ingots were poured with and without electromagnetic rotating field and then the graphite morphology was analysed. The electromagnetic rotating field can improve the graphite morphology.