Applied sciences

Archives of Foundry Engineering

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Archives of Foundry Engineering | 2020 | vol. 20 | Ahead of print |

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Abstract

The paper indicates the significance of the problem of foundry processes parameters stability supervision and assessment. The parameters, which can be effectively tracked and analysed using dedicated computer systems for data acquisition and exploration (Acquisition and Data Mining systems, A&D systems) were pointed out. The state of research and methods of solving production problems with the help of computational intelligence systems (Computational Intelligence, CI) were characterised. The research part shows capabilities of an original A&DM system in the aspect of selected analyses of recorded data for cast defects (effect) forecast on the example of a chosen iron foundry. Implementation tests and analyses were performed based on selected assortments for grey and nodular cast iron grades (castings with 50 kg maximum weight, casting on automatic moulding lines for disposable green sand moulds). Validation tests results, applied methods and algorithms (the original system’s operation in real production conditions) confirmed the effectiveness of the assumptions and application of the methods described. Usability, as well as benefits of using A&DM systems in foundries are measurable and lead to stabilisation of production conditions in particular sections included in the area of use of these systems, and as a result to improvement of casting quality and reduction of defect number.

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Authors and Affiliations

R. Sika
Z. Ignaszak
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Abstract

The article focuses on the analysis of the effect of Zr on the properties of the aluminium alloy AlSi9Cu1Mg. The effect of Zr was evaluated depending on the change in mechanical properties and heat resistance during a gradual addition of Zr with an increase of 0.05 wt. % Zr. Half of the cast experimental samples from each variant were heat treated by precipitation hardening T6 (hereinafter HT). The measured values in both states indicate an improvement of the mechanical properties, especially in the experimental variants with a content of Zr ≥ 0.20 wt. %. In the evaluation of Rm, the most significant improvement occurred in the experimental variant with an addition of Zr 0.25 wt. % after HT and E in the experimental variant with addition of Zr 0.20 wt. % after HT. Thus, a difference was found from the results of the authors defining the positive effect of Zr, in particular at 0.15 wt. %. When evaluating the microstructure of the AlSi9Cu1Mg alloy after Zr alloying, Zr phases are already eliminated with the addition of Zr 0.10 wt. %. Especially at higher levels of Zr ≥ 0.20 wt. %, long needle phases with slightly cleaved morphology are visible in the metal matrix. It can be stated that a negative manifestation of Zr alloying is expressed by an increase in gassing of experimental alloys, especially in variants with a content of Zr ≥ 0.15 wt. %. Experimental samples were cast into ceramic moulds. The development of an experimental alloy AlSi9Cu1Mg alloyed with Zr would allow the production of a more sophisticated material applicable to thin-walled Al castings capable of operating at higher temperature loads.

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Authors and Affiliations

M. Matejka
M. Kuriš
D. Bolibruchova
R. Pastirčák
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Abstract

The paper presents the results of an investigation of the gases emission of moulding sands with an inorganic (geopolymer) binder with a relaxation additive, whose main task is to reduce the final (residual) strength and improves knocking-out properties of moulding sand. The moulding sand without a relaxation additive was the reference point. The research was carried out using in accordance with the procedure developed at the Faculty of Foundry Engineering of AGH - University of Science and Technology, on the patented stand for determining gas emissions. Quantification of BTEX compounds was performed involving gas chromatography method (GC).The study showed that the introduction of relaxation additive has no negative impact on gas emissions - both in terms of the total amount of gases generated, as well as emissions of BTEX compounds. Among the BTEX compounds, only benzene is emitted from the tested moulding sands. Its emission is associated with the introduction a small amount of an organic hardener from the group of esters.

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Authors and Affiliations

A. Bobrowski
S. Żymankowska-Kumon
K. Kaczmarska
D. Drożyński
B. Grabowska
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Abstract

In the present work, different Cu-alloyed model ductile irons with ferritic (0%Cu-0.09%Mn), mixed ferritic-pearlitic (0.38%Cu-0.40%Mn) and pearlitic (0.69%Cu-0.63%Mn) microstructure were produced and analyzed in terms of their electrochemical corrosion behavior in a 3.5wt.%NaCl aqueous solution containing naturally dissolved oxygen at room temperature (25°C). The remaining elements such as Si and Mg were kept at balanced levels in an attempt to minimize variations in graphite size and distribution among different samples. The corrosion resistance was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization. Microstructure analysis of the cast alloys confirmed similarity in the graphite morphology among the different cast samples and the expected variations in the metallic matrix. In the absence of passivation, it was found that the addition of copper led to an increase in corrosion resistance, which could be attested by higher values polarization resistance and corrosion potential.

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Authors and Affiliations

P. Brito
W. Pereira
W. Santos
H. Gomes
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Abstract

The mathematical model and numerical simulations of the solidification of a cylindrical casting, which take into account the process of the mould cavity filling by liquid metal and the feeding of the casting through the conical riser during its solidification, are proposed in the paper. The interdependence of thermal and flow phenomena were taken into account because they have an essential influence on solidification process. The effect of the pouring temperature and pouring velocity of the metal on the solidification kinetics of the casting was determined. In order to obtain the casting without shrinkage defects, an appropriate selection of these parameters was tried, which is important for foundry practice. The velocity fields have been obtained from the solution of Navier-Stokes equations and continuity equation, while temperature fields from solving the equation of heat conductivity containing the convection term. In the solidification modelling the changes in thermo-physical parameters as a function of temperature were considered. The finite element method (FEM) was used to solve the problem.

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Authors and Affiliations

L. Sowa
T. Skrzypczak
P. Kwiatoń
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Abstract

The paper presents an analysis of a selected grade of high silicon cast iron intended for work in corrosive and abrasive conditions. The text describes its microstructure taking into account the process of crystallization, TDA analysis, EDS, XRD and the chemical composition analysis. In order to determine the phase composition, X-ray diffraction tests were carried out. The tests were executed on a Panalytical X'Pert PRO X-ray diffractometer with filtration of radiation from a lamp with copper anode and PIXcel 3D detector on the deflected beam axis. Completed tests allowed to describe the microstructure with detailed consideration of intermetallic phases present in the alloy. Results of the analysis of the examined alloy clearly show that we deal with intermetallic phases of Fe3Si, Fe5Si3 types, as well as silicon ferrite and crystals of silicon. In the examined alloy, we observed the phenomenon of segregation of carbon, which, as a result of this process, enriches the surface of silicon crystals, not creating a compound with it. Moreover, the paper demonstrates capability for crystallization of spheroidal graphite in the examined alloy despite lack of elements that contribute to balling in the charge materials.

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Authors and Affiliations

M. Stawarz
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Abstract

Filtration is one of the most efficient methods of removing Al2O3 inclusions from liquid steel. The efficiency of this process depends on the physicochemical parameters of liquid metal, inclusion and properties of the applied filters. The particles attracted during filtration undergo agglomeration, collisions and chemical reactions on the filter surface, with the emphasis on the mechanism of particle collisions and the role of material from which the filter was made. The aluminum oxide inclusions collide with the filter surface and as the growing process continues, the particles also collide with the previously adsorbed inclusions. At the interface of particle and filter the mixing of the metal bath is most intense, being a result of a sudden change of flow direction and breaking up the stream of liquid metal which is in a direct contact with material. The efficiency of filtration is defined not only by the behavior of individual particles but of all population. The simulations revealed that only a small fraction of these particles adheres directly to the filter material; most of them stick to the former ones. Attention should be also paid to the fact that some of the inclusions which contacted the filter walls do not form a permanent connection and are then entrained by metal. Authors solved the problem of agglomeration and collisions of Al2O3 inclusions with the ceramic surface of the filter with the PSG method, mainly used for the analysis of agglomeration of inclusions during steel refining in the ladle.

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Authors and Affiliations

D. Kalisz
K. Kuglin
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Abstract

The paper presents the results of research on microstructure and impact strength of AlSi13Cu2 matrix composite reinforced by Ni-coating carbon fibers (CF) with a volume fraction of 5%, 10% and 15%. The composite suspensions were prepared using by stirring method and subsequently squeeze casted under different pressures of 25, 50, 75 and 100 MPa. As part of the study, fiber distribution in aluminum matrix was evaluated and variation in impact strength of composite as a function of the carbon fibers volume fraction and pressure applied were determined. It has been found that the presence of Ni coating on carbon fibers clearly improves their wettability by liquid aluminum alloy and in combination with the stirring parameters applied, composite material with relatively homogeneous structure can be produced. Charpy's test showed that the impact strength of composite reaches the highest value by carrying out the squeeze casting process at 75 MPa. In the next stage of research, it was found that the impact strength of composites increases with the increase of carbon fibers volume fraction and for 15% of fibers is close to 8 J/cm2. Observations of fracture surfaces have revealed that crack growth in the composites propagates with a quasi-cleavage mechanism. During the creation of the fracture, all fibers arranged perpendicular to its surface were sheared. At the same time, the metal matrix around the fibers deformed plastically creating characteristic ductile breaks. The fracture surface formation through the fibers indicates a cohesive and strong connection of the reinforcement with the matrix. In addition to the phenomena mentioned, debonding the fiber-matrix interfaces and the formation of voids between components were observed on the fracture surface.

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Authors and Affiliations

A. Zyska
Z. Konopka
M. Łągiewka
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Abstract

The removal of inclusions is a major challenge prior to the casting process, as they cause a discontinuity in the cast material, thereby lowering its mechanical properties and have a negative impact on the feeding capability and fluidity of the liquid alloys. In order to achieve adequate melt quality for casting, it is important to clean the melts from inclusions, for which there are numerous methods that can be used. In the course of the presented research, the inclusion removal efficiency of rotary degassing coupled with the addition of different fluxes was investigated. The effects of various cleaning fluxes on the inclusion content and the susceptibility to pore formation were compared by the investigation of K-mold samples and the evaluation of Density Index values at different stages of melt preparation. The chemical composition of the applied fluxes was characterized by X-ray powder diffraction, while the melting temperature of the fluxes was evaluated by derivatographic measurements. It was found that only the solute hydrogen content of the liquid metal could be significantly reduced during the melt treatments, however, better inclusion removal efficiency could be achieved with fluxes that have a low melting temperature.

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Authors and Affiliations

M. Máté
M. Tokár
G. Fegyverneki
G. Gyarmati
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Abstract

The paper presents the preliminary results of research on determining the possibilities of using available on the market commercial gypsum kinds as a binder for foundry moulding and core sandmixes. Construction gypsum and plaster gypsum, finishing coat and jewelry casting gypsum were tested. Elemental composition of gypsum kinds were carried out using a scanning electron microscope (SEM) with EDS/EDX probe, their crystal structure and phase composition was determined by analyzing the results of X-ray diffraction measurements (XRD) and thermogravimetric studies (TG-DTA). Evaluation of the mechanical properties of selected materials was carried out at the tensile strength test of the dog-bone samples after initial hardening of gypsum mortar at 25 °C for 5 h and drying at 110 °C for 24 hours. The impact of the properties of the used commercial gypsum kinds on the possibility of their use as a valuable binders in the manufacture of the foundry sandmixes for moulds and cores was evaluated. Construction gypsum and finishing coat have the highest tensile strength. Plaster gypsum and finishing coat have the longest setting time. In all tested types of gypsum, the initial water loss during heating occurs at a temperature of about 200 °C. The lowest valuable properties as a binder for sand moulding mixtures has jewelry casting gypsum mass.

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Authors and Affiliations

P. Paduchowicz
M. Stachowicz
A. Baszczuk
M. Hasiak
K. Granat
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Abstract

This article presents a study of the crystallization and microstructure of the AlSi9 alloy (EN AC-AlSi9) used for the alfin processing of iron ring supports in castings of silumin pistons. Alfin processing in brief is based on submerging an iron casting in an Al-Si bath, maintaining it there for a defined time period, placing it in a chill mould casting machine and immersing it in the alloy. This technology is used for iron ring supports in the pistons of internal combustion engines, among others. Thermal analysis shows that when the AlSi9 alloy contains a minimal content of iron, nucleation and increase in the triple (Al)+Fe+(Si) eutectic containing the -Al8Fe2Si phase takes place at the end of the crystallization of the double (Al)+(Si) eutectic. Due to the morphology of the ”Chinese script” the -Al8Fe2Si phase is beneficial and does not reduce the alloy’s brittleness. After approx. 5 hours of alfin processing, the -Al5FeSi phase crystallizes as a component of the +Al5FeSi+(Si) eutectic. Its disadvantageous morphology is ”platelike” with sharp corners, and in a microsection of the surface, ”needles” with pointed corners are visible, with increases the fragility of the AlSi9 alloys.

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Authors and Affiliations

J. Piątkowski
M. Czerepak
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Abstract

The analysis of after reclamation dusts generated during the reclamation treatment of test portions of two kinds of polydispersive material in the Regmas device, is presented in the hereby paper. For the comparative purpose the fresh moulding sand marked as quartz sand „Sibelco” –1K 0.40/0.32/0.20, J88, >14000C, WK = 1.20 (acc. PN-83/H-11077), as well as the spent moulding sand, which was previously subjected to the primary reclamation and to dedusting, were used. Conditions of the process treatment were forced by the frequency of supplying the vibratory drive motors being successively 40, 50 and 60Hz for 5, 10 and 15 min. and by causing a diversified material flow through the functional system of the device (charging hopper, abrasive chamber acting as a buffer space). Two states of the process treatment, when a material was flowing through the chamber, were applied. In the first one, an intergranular surface abrasion of grains occurred as a result of the granular material circulation in the chamber forced by the vibratory drive. In the second one, the forced material flow was performed in the presence of crushing elements (steel balls), additionally introduced into the abrasive chamber. Analyses of the device influence were performed by determinations of the amount of dusts separated in the pneumatic classifier and analysis of their grain sizes by means of Analysette 22NanoTec.

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Authors and Affiliations

M. Skrzyński
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Abstract

The effect of vanadium microaddition on the strength of low-carbon cast steel containing 0.19% C used, among others, for castings of slag ladles was discussed. The tested cast steel was melted under laboratory conditions in a 30 kg capacity induction furnace. Mechanical tests were carried out at 700, 800 and 900°C using an Instron 5566 machine equipped with a heating oven of  2C stability. Non-standard 8- fold samples with a measuring length of 26 mm and a diameter of 3 mm were used for the tests. It has been shown that, compared to cast steel without vanadium microaddition, the introduction of vanadium in an amount of 0.12% to unalloyed, low carbon cast steel had a beneficial effect on the microstructure and properties of this steel not only at ambient temperature but also at elevated temperatures when it promoted an increase in UTS and YS. The highest strength values were obtained in the tested cast steel at 700C with UTS and YS reaching the values of 193 MPa and 187.7 MPa, respectively, against 125 MPa and 82.8 MPa, respectively, obtained without the addition of vanadium. It was also found that with increasing test temperature, the values of UTS and YS were decreasing. The lowest values of UTS and YS obtained at 900°C were 72 MPa and 59.5 MPa, respectively, against 69 MPa and 32.5 MPa, respectively, obtained without the addition of vanadium.

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Authors and Affiliations

B.E. Kalandyk
R.E. Zapała
P. Pałka
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Abstract

The usage of the reduced pressure in the processes of smelting and refining of metal alloys allow to remove not only the gases dissolved in the metal bath, but also the impurities having a higher vapour pressure than the matrix metal. Blister copper produced in flash furnace contains many impurities such as lead, bismuth and arsenic. Some of them must be removed from molten metals, because of their deleterious effects on copper electrical properties. When the smelting process is carried out in the induction vacuum furnaces, the abovementioned phenomenon is being intensified, one or another mixing of bath and increase in the surface area of mass exchange (liquid metal surface). The latter results from the formation of a meniscus being an effect of the electromagnetic field influence on the liquid metal. In the work, the results of refining blister copper in terms of removing lead from it, are presented. The experiments were carried out in the induction crucible vacuum furnace at temperatures of 1473 and 1523 K, and operating pressures in a range of 8 - 533 Pa.

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Authors and Affiliations

A. Smalcerz
L. Blacha
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Abstract

The morphology of G20Mn5 specimens made of non-modified and rare earth metals (REM) modified cast steel was investigated. Molten metal was treated with a cerium-rich mischmetal contain 49.8% Ce, 21.8% La, 17.1% Nd, 5.5% Pr and 5.35% other rare earth metals making up the balance. The melting, quenching (920°C/water) and tempering (720°C/air) were performed under industrial conditions. Analysis included G20Mn5 cast steel fracture specimens subjected to Charpy V-notch impact testing at 20°C, -30°C and -40°C. The purpose of the analysis was to determine the influence of REM on the microstructure and mechanical properties of G20Mn5 cast steel and the REM effect on the morphology, impact strength and character of the fracture surfaces. In addition, a description of the mechanism by which fracture occurred in the two materials was proposed. The author demonstrated the beneficial effects of adding REM to molten steel, manifested by a 20 - 40% increase in impact toughness, depending on test temperature, as compared to the non-modified cast steel. Important findings included more than 100% increase in impact strength in comparison with the required impact toughness of 27J at -40C for heat treated steels (EN 10213).

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Authors and Affiliations

J. Kasińska

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J. Szajnar
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Theoretical Aspects of Casting Processes
K. Eigenfeld – Freiberg, Germany
E. Guzik – Kraków, Poland
T. G. Mathia - Lyon, France
W. Wołczyński – Kraków, Poland
Innovative Foundry Technologies and Materials
T. Elbel – Ostrava, Czech Republic
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O. P. Pandey – Punjab, India
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B. Mochnacki – Częstochowa, Poland
J. Roučka – Brno, Czech Republic
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J. Bast – Freiberg, Germany
R. Wrona – Kraków, Poland
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J. Dańko – Kraków, Poland
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