Nauki Techniczne

Archives of Foundry Engineering

Zawartość

Archives of Foundry Engineering | 2018 | vol.18 | No 4 ahead of print |

Abstrakt

Production processes at KGHM are complex and require from customers products of constantly higher quality at relatively lowest prices. Such situation results in an increase of the importance of optimisation of processes. As products and technologies change rapidly, technologists at the plant in Głogów have less time to achieve optimisation basing on own experiences. Analysing a particular process, we can e.g. detect occurring disturbances, find factors having an influence on quality problems, select optimal settings or compare various production procedures. Analysis of the course of production process is the basis of process optimisation. One optimisation in case of the process of decopperisation of flash slag can be a change of a technological additive to a less energy-consuming one, and its final result can be an improvement of the productivity index, a change of the relation between final effects and born expenditures, as well as optimisation of production costs.

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With increasing technology development, an increasing emphasis is placed on the precision of products, but cannot be guaranteed without a stable production process. To ensure the stability of the production process, it is necessary to monitor it in detail, find its critical locations and eliminate or at least control it. With such a precise manufacturing method as investment casting, such a process is a must. This paper therefore deals with monitoring the production process of wax models of large turbine blades using infrared thermography. The aim was to evaluate the critical locations of this production and to propose recommendations for their elimination or, at the very least, significant mitigation of their impact on the final quality of the large turbine blade casting.

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Mechanical reclamation process of spent moulding sands generate large amounts dusts containing mainly rubbed spent binding agents and quartz dust. The amounts of post-reclamation dusts, depending of the reclamation system efficiency and reclaim dedusting system, can reach 5 -10% in relation to the total reclaimed moulding sand. This dust due to the high content of the organic substances is a threat to the environment and therefore requires the storage on landfills specially adapted for this type of waste. On the other hand, the presence of organic substances causes that these dusts have relatively high energy values that could be used. However, at present there is no coherent, environmentally friendly concept for the management of this type of dust. The paper presents the results of tests of thermal utilization the dusts (as a source of energy) were carried out at AGH University of Science and Technology. Thermal utilization of dusts was carried out in the co-burning with carbon carriers process or in individual burning (Patent PL 227878 B1 and patent application PL - 411 902).

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Inconel 713C alloy belongs to the group of materials with high application potential in the aerospace industry. This nickel alloy has excellent features such as high strength, good surface stability, high creep and corrosion resistance. The paper presents the results of metallographic examinations of a base material and padding welds made by laser beam on the Inconel 713C alloy. The tests were made on precisely cast test plates imitating low - pressure turbine blades dedicated for the aerospace industry. Observations of the macro- and microstructure of the padding welds, heat-affected zone and base material indicate, that the Inconel 713C alloy should be classified as a hard-to-weld material. In the investigated joint, cracking of the material is disclosed mainly in the heat-affected zone and at the melted zone interface, where pad weld crystals formed on partially melted grains. The results show that phases rich with chromium and molybdenum were formed by high temperature during welding process, which was confirmed by EDS analysis of chemical composition.

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Secondary or multiple remelted alloys are common materials used in foundries. For secondary (recycled) Al-Si-Cu alloys, the major problem is the increased iron presence. Iron is the most common impurity and with presence of other elements in alloy creates the intermetallic compounds, which may negatively affect the structure. The paper deals with effect of multiple remelting on the microstructure of the AlS9iCu3 alloy with increased iron content to about 1.4 wt. %. The evaluation of the microstructure is focused on the morphology of iron-base intermetallic phases in caste state, after the heat treatment (T5) and after natural aging. The occurrence of the sludge phases was also observed. From the obtained results can be concluded that the multiple remelting leads to change of chemical composition, changes in the final microstructure and also increases sludge phases formation. The use of heat treatment T5 led to a positive change of microstructure, while the effect of natural aging is beneficial only to the 3rd remelting.

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A common problem encountered in hydraulic valves is a progressing deterioration of tightness of their water flow cutting-off seats. The seats are provided usually with a copper-alloy insert joined mechanically with cast-iron valve housing. The problem of unreliability of such joints can be solved by providing surface of the seat with a coating, deposited with the use of HVOF method and resistant to abrasive and cavitation wear. The tests were carried out for a sealing-draining seat insert made of CuZn39Pb2Al brass used to date and a specimen taken from the cast-iron valve housing which was the substrate for a plasma-sprayed coating of powder containing 86.1% Cr, 7.2% Ni, and 6.7% C. The coating, 345 ± 15 μm thick, was characterized with good quality of bonding with cast-iron substrate and high compactness of the material. The cavitation wear test on materials used in the study were carried out with the use of Vibra-Cell ultrasonic liquid processor (Sonics) equipped with a piezoelectric probe operating at the frequency of 20 kHz. Based on profilograms taken along a line crossing centers of cavitation craters, measurements of the height parameter Rt, and microscopic observations of surfaces it has been found that the coating plasma-sprayed onto substrate of nodular cast iron demonstrated higher resistance to cavitation compared to copper-alloy inserts used so far in cast-iron hydraulic valves. Cavitation craters on the material used typically for valve seats to date were more distinctly outlined and deeper compared to craters observed on the coating. Larger were also sizes of local tear-outs which resulted in larger difference between the peaks line and the valleys line.

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The paper deals with the issue of potential for improvement of resistance of wood chip fine grinders to abrasive wear by providing them with WCCoCr coating applied with the use of atmospheric plasma spraying (APS). The study focused on establishing parameters of the technological process of spraying a 250–270 μm thick coating onto surface of ductile cast iron castings used to date as grinder linings. The presented data include results of microstructure examination, chemical composition analysis, HV hardness measurements, and scratch tests for both previous and new variant of linings. The obtained scratch test results indicate that the material of the coating is characterized with definitely lower susceptibility to scratching. The scratch made on coating was 75–84 μm wide and 7.2–8.2 μm deep, while the scratch on cast iron was distinctly wider (200–220 μm) and deeper (8.5–12.8 μm). In case of cast iron, the range of variability in scratch width and depth was definitely larger. This can be explained with large difference in hardness of individual components of microstructure of cast iron and significantly larger plastic deformation of cast iron compared to the coating revealed in the course of indenter motion over surfaces of the two materials. It has been found that application of WCCoCr coating offered better resistance of lining surfaces to scratching which can be considered a rationale for undertaking in-service tests.

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The article presents the investigations of 7xxx aluminium alloys performed by the method of thermal and derivational analysis. The studies made it possible to identify the effect of the changes in the Cu concentration, the total Zn and Mg weight concentrations and the Zn/Mg weight concentration ratio on their crystallization process: the cooling as well as the kinetics and dynamics of the thermal process of cooling and crystallization. Metallographic studies were performed on the microstructure of the examined alloys and their HB hardness was measured. The evaluation of the changes was presented in reference to the model alloys EN AW-7003 and EN AW-7010, whose microstructure under the conditions of thermodynamic equilibrium are described by the phase diagrams: Al-Zn-Mg and Al-Zn-Mg-Cu. The performed investigations confirmed that the hardness HB of the examined alloys is mainly determined by the reinforcement of the matrix αAl by the introduced alloy additions and the presence of phases Θ(Al2Cu) and S(Al2CuMg) rich in copper, as well as η(MgZn2), in the examined alloys' microstructure. The increase of the amount of intermetallic phases precipitated in the microstructure of the examined alloys is caused, beside Cu, by the characteristic change of Zn wt. concentration and Mg. It was proposed that the process of one-stage thermal treatment of the examined alloys be introduced at a temperature of up to tJ-20 °C, which will prevent the exceedance of the solidus temperature.

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The use of environmentally friendly inorganic binders and new technologies for cores production is widely discussed topic in recent years. This paper contains information about new hot curing process for core making with alumina-silicate based inorganic binders – geopolymers. Main differences between hot cured geopolymers and hot cured alkali silicate based inorganic binders are discussed. The main objective of this research paper was to investigate basic technological properties of geopolymer binder system such as strength, compaction, storage ability and knock-out properties. For this purpose, three mixtures with different powder additives were prepared and tested in laboratory conditions using specific methods. Strength properties evaluation showed sufficient levels as well as knock-out properties measurement, even with additives B and C originally designed for the use with alkali silicate based two component binder systems. Additives B and C were considered compatible with geopolymer binders after casting production trial results. Storage ability of geopolymers seems to be more sensitive than of alkali silicate based binders in the same tested conditions. Mixtures with geopolymer binder showed 20% more decrease of strength compared to alkali silicate binders after 24 hours in conditions of 25 °C and 65 %RH.

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In the family of iron-based alloys, ductile iron enjoys the highest rate of development, finding application in various industries. Ductile iron or the cast iron with spheroidal graphite can be manufactured by various methods. One of them is the Inmold spheroidization process characterized by different technological solutions, developed mainly to increase the process efficiency. So far, however, none of the solutions has been based on the use of a reactor made outside the casting mould cavity. The method of spheroidization inside the casting mould using a reaction chamber developed at the Foundry Research Institute is an innovative way of cast iron treatment. The innovative character of this method consists in the use of properly designed and manufactured reactor placed in the casting mould cavity. Owing to this solution, the Inmold process can be carried out in moulds with both horizontal and vertical parting plane. The study presents the results of examinations of the microstructure of graphite precipitates and metal matrix of castings after spheroidization carried out by the Inmold process using a reactor and mould with vertical parting plane. Special pattern assembly was made for the tests to reproduce plates with wall thicknesses of 3; 5; 7; 10; 20 and 30 mm. The content of residual magnesium was determined for all tested castings, while for castings of plates with a wall thickness equal to or larger than 10 mm, testing of mechanical properties was additionally performed.

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The constantly developing and the broadly understood automation of production processes in foundry industry, creates both new working conditions - better working standards, faster and more accurate production - and new demands for previously used materials as well as opportunities to generate new foundry defects. Those high requirements create the need to develop further the existing elements of the casting production process. This work focuses on mechanical and thermal deformation of moulding sands prepared in hot-box technology. Moulding sands hardened in different time periods were tested immediately after hardening and after cooling. The obtained results showed that hardening time period in the range 30-120 sec does not influence the mechanical deformation of tested moulding sands significantly. Hot distortion tests proved that moulding sands prepared in hot-box technology can be characterized with stable thermal deformation up to the temperature of circa 320oC.

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The paper presents the theory of constraints (TOC) as a method used to improve results in a complex, multiplants organization. In the article the assumptions of this method has been presented as well as iterative approach concerning how to launch it in practice. Main indicators for organizational effectiveness assessment have also been presented. The maximization of production assets utilization is a key issue for competitive organization in the changing market conditions. An appropriate usage of the theory of constraints enables efficient allocation of financial assets among particular plants within a capital group. An application of a method has been presented based on throughput analyses and its influence to improve financial results of one plant organization and synergy effect in multiplants organization. The theory of constraints can be used in almost every kind of business sectors, among them are metal and foundry industries. It allows to be implemented in production organizations as well as in any other company’s profiles. Everywhere the constraint has been defined there is a chance to achieve an improvement following the presented method. The examples have been taken from the casting plants which use continuous and mold casting technologies. The examples show that TOC approach can be successfully employed as the improvement tool of foundries’ performances.

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The results of studies presented in this article are an example of the research activity of the authors related to lead-free alloys. The studies covered binary SnZn90 and SnZn95 lead-free alloys, including their microstructure and complex mechanical characteristics. The microstructure was examined by both light microscopy (LM) and scanning electron microscopy (SEM). The identification of alloy chemical composition in micro-areas was performed by SEM/EDS method. As regards light microscopy, the assessment was of both qualitative and quantitative character. The determination of the geometrical parameters of microstructure was based on an original combinatorial method using phase quantum theory. Comprehensive characterization of mechanical behavior with a focus on fatigue life of alloys was performed by means of the original modified low cycle fatigue method (MLCF) adapted to the actually available test machine. The article discusses the fatigue life of binary SnZn90 and SnZn95 alloys in terms of their microstructure. Additionally, the benefits resulting from the use of the combinatorial method in microstructure examinations and MLCF test in the quick estimation of several mechanical parameters have been underlined.

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In this work, the effects of 75 mm thick cast iron, (casting mould YIV) composition (Cu) and heat treatment were investigated on the microstructure and mechanical properties (hardness, elongation, tensile strength, yield strength) of ductile iron castings. As a result of adding Cu, the amount of pearlite is at 80% reduces of amount of ferrite. Normalizing of non-alloy cast iron increases the amount of pearlite to 70%. It also, increases tensile strength (659 MPa) and hardness (248 HB). Studied metallographic crossections were made from the grip sections of the tensile specimens. The structure composition and the characteristics of graphite were determined by computer image analysis. Measurements of graphite of non-alloy cast iron after normalizing and in cooper cast iron indicate the approximate amount of precipitates of graphite and their approximate average diameters. The applied normalizing and the additive alloy (Cu) were established to give comparable mechanical properties and structure of matrix in thick-walled castings.

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The results of statistical analysis applied in order to evaluate the effect of the high melting point elements to pressure die cast silumin on its tensile strength Rm, unit elongation A and HB were discussed. The base alloy was silumin with the chemical composition similar to ENAC 46000. To this silumin, high melting point elements such as Cr, Mo, V and W were added. All possible combinations of the additives were used. The content of individual high melting point additives ranged from 0.05 to 0.50%. The tests were carried out on silumin with and without above mentioned elements. The values of Rm, A and HB were determined for all the examined chemical compositions of the silumin. The conducted statistical analysis showed that each of the examined high melting point additives added to the silumin in an appropriate amount could raise the values of Rm, A and HB. To obtain the high tensile strength of Rm = 291 MPa in the tested silumin, the best content of each of the additives should be in the range of 0.05-0.10%. To obtain the highest possible elongation A of about 6.0%, the best content of the additives should be as follows: chromium in the range of 0.05-0.15%, molybdenum 0.05% or 0.15%, vanadium 0.05% and tungsten 0.15%. To obtain the silumin with hardness of 117 HB, chromium, molybdenum and vanadium content should be equal to about 0.05%, and tungsten to about 0.5%.

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Redakcja

CHIEF EDITORS
Editor
J. Szajnar
Deputy Editor
J. Jezierski

SUBJECT EDITORS
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
Z. Ignaszak – Poznań, Poland
O. P. Pandey – Punjab, India
A. Pereira - Vigo, Spain
Foundry Processes Computer Aiding
B. Mochnacki – Częstochowa, Poland
J. Roučka – Brno, Czech Republic
J.S. Suchy – Kraków, Poland
Mechanization, Automation and Robotics in Foundry
J. Bast – Freiberg, Germany
R. Wrona – Kraków, Poland
Transport Systems in Foundry
J. Dańko – Kraków, Poland
Z. Li – Shijiazhuang, China
Castings Quality Management
D. Bolibruchova– Żilina, Slovak Republic
J. D. B. de Mello - Santa Monica, Brazil
M. Perzyk – Warszawa, Poland
Environment Protection
M. Holtzer – Kraków, Poland
H. Polzin – Freiberg, Germany
J. Sobczak – Kraków, Poland
I. Volchok – Zaporizhzhya, Ukraine

EDITORIAL ADVISORY BOARD
J. Braszczyński – Częstochowa, Poland
B. K. Dhindaw – Rupnagar, India
L. A. Dobrzański – Gliwice, Poland
W. A. Hufenbach – Dresden, Germany
P. Jelínek – Ostrava, Czech Republic
L. Jeziorski – Częstochowa, Poland
J. Lacaze – Toulouse, France
V. L. Naydek – Kiev, Ukraine
A. Passerone – Genova, Italy
I. Riposan – Bucharest, Romania
F. Romankiewicz – Zielona Góra, Poland
A. Sládek – Żilina, Slovak Republic

INTERNATIONAL SCIENTIFIC REVIEW COMMITTEE
S. A. Argyropoulos – Toronto, Canada
M. Azadi – Tehran, Iran
Y. Babaskin – Kiev, Ukraine
K. Bako – Miskolc, Hungary
E. Bayraktar – Paris, France
L. Bechný – Zilina, Slovak Republic
V. Bednarova - Ostrava, Czech Republic
F. Bińczyk – Katowice, Poland
A. Bokota – Częstochowa, Poland
G.P. Borisov – Kiev, Ukraine
A. Bydałek – Kraków, Poland
C. H. Cáceres – Brisbane, Australia
J. Čech – Brno, Czech Republic
L. Q. Chen – Shenyang, China
A. Chojecki – Kraków, Poland
M. Cholewa – Gliwice, Poland
I. A. Dibrov – Moscow, Russia
D. Dispinar – Istanbul, Turkey
S. M. Dobosz – Kraków, Poland
V. I. Dubodelov – Kiev, Ukraine
A. Fedoryszyn – Krakow, Poland
J. Głownia – Kraków, Poland
K. Granat – Wrocław, Poland
J. Hampl – Ostrava, Czech Republic
J. Helber – Düsseldorf, Germany
M. Hetmańczyk – Katowice, Poland
M. Horáček – Brno, Czech Republic
M. Kaczorowski – Warszawa, Poland
W. Kapturkiewicz – Kraków, Poland
R. Kawalla – Freiberg, Germany
Z. Konopka – Czestochowa, Poland
D. Kopyciński – Kraków, Poland
W. K. Krajewski – Kraków, Poland
Z. Libo – Beijing, China
P. Lichy – Ostrava, Czech Republic
Y. P. Lim – Setapak, Malaysia
T. Lipiński – Olsztyn, Poland
E. Majchrzak – Gliwice, Poland
A. Mityayev - Zaporizhzhya, Ukraine
M. Murgaš – Trnava, Slovak Republic
I. Nová – Liberec, Czech Republic
W. Orłowicz – Rzeszów, Poland
T. Pacyniak – Łódź, Poland
B. Piekarski – Szczecin, Poland
A. Rimmer – West Bromwich, United Kingdom
S. Samavedam – Hyderabad, India
P. Schumacher – Leoben, Austria
N. Sczygiol – Częstochowa, Poland
P. Skočovský – Żilina, Slovak Republic
M.S. Soiński – Częstochowa, Poland
J. Sokolowski – Ottawa, Kanada
K. V. Sudhakar – Butte, USA
B. G. Thomas - Champaign, USA
M. Trbižan – Ljubljana, Slovenia
J. Vuorinen – Tampere, Finland
E. Ziółkowski – Kraków, Poland
J. Zych – Kraków, Poland

ASSOCIATE EDITORS
D. Bartocha – Gliwice, Poland, - editorial secretary
J. Suchoń – Gliwice, Poland - editorial secretary
J. Szymszal – Katowice, Poland, Statistic Editor
A. Dulska – Gliwice, Poland
M. Kondracki – Gliwice, Poland
C. Borek –Chicago, USA, Language Editor

 

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