Archives of Foundry Engineering

The paper discusses the impact of the geometry of foundry pallet components on the value of temperature gradient on the wall crosssection

during heat treatment. The gradient is one of the most important factors determining the distribution of thermal stresses in these

items. Analysis of quantitative simulation was carried out to detect possible effect of the type of connection between pallet walls and

thickness of these walls (ribs) on the interior temperature distribution during rapid cooling. The analysis was performed for five basic

designs of wall connections used in pallets. Basing on the results obtained, the conclusions were drawn on the best connection between the

ribs in foundry pallets.

This paper deals with influence on segregation of iron based phases on the secondary alloy AlSi7Mg0.3 microstructure by chrome. Iron is

the most common and harmful impurity in aluminum casting alloys and has long been associated with an increase of casting defects. In

generally, iron is associated with the formation of Fe-rich phases. It is impossible to remove iron from melt by standard operations, but it is

possible to eliminate its negative influence by addition some other elements that affect the segregation of intermetallics in less harmful

type. Realization of experiments and results of analysis show new view on solubility of iron based phases during melt preparation with

higher iron content and influence of chrome as iron corrector of iron based phases. By experimental work were used three different

amounts of AlCr20 master alloy a three different temperature of chill mold. Our experimental work confirmed that chrome can be used as

an iron corrector in Al-Si alloy, due to the change of intermetallic phases and shortening their length.

The generic mathematical model and computational algorithm considering hydrodynamics, heat and mass transfer processes during casting

and forming steel ingots and castings are offered. Usage domains for turbulent, convective and non-convective models are determined

depending on ingot geometry and thermal overheating of the poured melt. The expert system is developed, enabling to choose a

mathematical model depending on the physical statement of a problem.

The powerful tool for defect analysis is an expert system. It is a computer programme based on the knowledge of experts for solving the

quality of castings. We present the expert system developed in the VSB-Technical University of Ostrava called ‘ESWOD’. The ESWOD

programme consists of three separate modules: identification, diagnosis / causes and prevention / remedy. The identification of casting

defects in the actual form of the system is based on their visual aspect.

A eutectic reaction is a basic liquid-solid transformation, which can be used in the fabrication of high-strength in situ composites.

In this study an attempt was made to ensure directional solidification of Fe-C-V alloy with hypereutectic microstructure. In this alloy, the

crystallisation of regular fibrous eutectic and primary carbides with the shape of non-faceted dendrites takes place. According to the data

given in technical literature, this type of eutectic is suitable for the fabrication of in-situ composites, owing to the fact that a flat

solidification front is formed accompanied by the presence of two phases, where one of the phases can crystallise in the form of elongated

fibres.

In the present study an attempt was also made to produce directionally solidifying vanadium eutectic using an apparatus with a very high

temperature gradient amounting to 380 W/cm at a rate of 3 mm/h. Alloy microstructure was examined in both the initial state and after

directional solidification. It was demonstrated that the resulting microstructure is of a non-homogeneous character, and the process of

directional solidification leads to an oriented arrangement of both the eutectic fibres and primary carbides.

In the paper the results and analysis of corrosion tests were presented for low-alloyed cast steel in as-cast state and after heat treatment

operations. Such alloys are applied for heavy loaded parts manufacturing, especially for mining industry. The corrosion test were

performed in conditions of high salinity, similar to those occurring during the coal mining. The results have shown, that small changes in

chemical composition and the heat treatment influence significantly the corrosion behaviour of studied low-alloyed cast steels.

The paper presents the method of preparing a composite slurry composed of AlSi11 alloy matrix and 10 vol.% of SiC particles, as well as

the method of its high-pressure die casting and the measurement results concerning the castability of the obtained composite. Composite

castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and

various injection gate width values. There were found the regression equations describing the change of castability of the examined

composite as a function of pressure die casting process parameters. The conclusion gives the analysis and the interpretation of the obtained

results.

The paper presents possibility of using biodegradable materials as parts of moulding sands’ binders based on commonly used in foundry

practice resins. The authors focus on thermal destruction of binding materials and thermal deformation of moulding sands with tested

materials. All the research is conducted for the biodegradable material and two typical resins separately. The point of the article is to show

if tested materials are compatible from thermal destruction and thermal deformation points of view. It was proved that tested materials

characterized with similar thermal destruction but thermal deformation of moulding sands with those binders was different.

This study discloses the characteristic features of the modified low-cycle fatigue test used for the determination of the mechanical

properties of two types of cast iron, i.e. EN-GJL-250 and EN-GJS-600-3. For selected materials, metallographic studies were also

conducted in the range of light microscopy and scanning microscopy.

Iron is the most common and detrimental impurity in casting alloys and has been associated with many defects. The main consequence of

the presence or adding of iron to AlSi alloys is the formation Fe-rich intermetallics with especially deleterious β-Al5FeSi. β-Al5FeSi phases

are most often called needles on 2D micro sections, whilst platelets in 3D geometry. The x-ray tomography results have demonstrated Ferich

phases with shapes different from simple forms such as needles or platelets and presented bent and branched phases. β grown as

complicated structure of bent and branched intermetallics can decrease feeding ability, strengthen pores nucleation and eutectic colonies

nucleation leading to lower permeability of mushy zone and porosity in the castings.

The quality of the squeeze castings is significantly affected by secondary dendrite arm spacing, which is influenced by squeeze cast input

parameters. The relationships of secondary dendrite arm spacing with the input parameters, namely time delay, pressure duration, squeeze

pressure, pouring and die temperatures are complex in nature. The present research work focuses on the development of input-output

relationships using fuzzy logic approach. In fuzzy logic approach, squeeze cast process variables are expressed as a function of input

parameters and secondary dendrite arm spacing is expressed as an output parameter. It is important to note that two fuzzy logic based

approaches have been developed for the said problem. The first approach deals with the manually constructed mamdani based fuzzy

system and the second approach deals with automatic evolution of the Takagi and Sugeno’s fuzzy system. It is important to note that the

performance of the developed models is tested for both linear and non-linear type membership functions. In addition the developed models

were compared with the ten test cases which are different from those of training data. The developed fuzzy systems eliminates the need of

a number of trials in selection of most influential squeeze cast process parameters. This will reduce time and cost of trial experimentations.

The results showed that, all the developed models can be effectively used for making prediction. Further, the present research work will

help foundrymen to select parameters in squeeze casting to obtain the desired quality casting without much of time and resource

consuming.

Simulation software can be used not only for checking the correctness of a particular design but also for finding rules which could be used

in majority of future designs. In the present work the recommendations for optimal distance between a side feeder and a casting wall were

formulated. The shrinkage problems with application of side feeders may arise from overheating of the moulding sand layer between

casting wall and the feeder in case the neck is too short as well as formation of a hot spot at the junction of the neck and the casting. A

large number of simulations using commercial software were carried out, in which the main independent variables were: the feeder’s neck

length, type and geometry of the feeder, as well as geometry and material of the casting. It was found that the shrinkage defects do not

appear for tubular castings, whereas for flat walled castings the neck length and the feeders’ geometry are important parameters to be set

properly in order to avoid the shrinkage defects. The rules for optimal lengths were found using the Rough Sets Theory approach,

separately for traditional and exothermic feeders.

Mechanical and technological properties of castings made from 3xx.x alloys depend mainly on properly performed process of melting and

casting, structure of a casting and mould, as well as possible heat treatment. Precipitation processes occurring during the heat treatment of

the silumins containing additives of Cu and/or Mg have effect on improvement of mechanical properties of the material, while choice of

parameters of solutioning and ageing treatments belongs to objectives of research work performed by a number of authors. Shortened heat

treatment, which is presented in the paper assures suitable mechanical properties (Rm), and simultaneously doesn’t cause any increase of

production costs of a given component due to long lasting operations of the solutioning and ageing. Results of the research concern effects

of the solutioning and ageing parameters on the Rm tensile strength presented in form of the second degree polynomial and illustrated in

spatial diagrams. Performed shortened heat treatment results in considerable increase of the Rm tensile strength of the 320.0 alloy as early

as after 1 hour of the solutioning and 2 hours of the ageing performed in suitable.

In the dissertation it has been shown, that so called „time-thermal treatment” (TTT) of the alloy in liquid state, as overheating the metal

with around 250o

C above the Tliq. and detaining it in this temperature for around 30 minutes, improves the mechanical properties (HB, Rm,

R0,2). It was ascertained, that overheating the AlSi17Cu5Mg alloy aids the modification, resulting with microcrystalline structure. Uniform

arrangement of the Si primeval crystals in the warp, and α(Al) solution type, supersaturated with alloying elements present in the base

content (Cu, Mg) assures not only increased durability in the ambient temperature, but also at elevated temperature (250o

C), what is an

advantage, especially due to the use in car industry.

In the dissertation it has been shown, that so called “time-thermal treatment” (TTT) of the alloy in liquid state as overheating the metal

with around 250o

C above Tliq. and detailing it in temperature for 30 to 40 minutes has the influence on changing the crystallization

parameters (Tliq., TEmin.

, TEmax., TE(Me), TSol.). It was ascertained, that overheating the AlSi17Cu5Mg alloy substantially above Tliq. results

with microcrystalline structure. Evenly distributed in the eutectic warp primeval silicon crystals and supersaturated with alloying additives

of base content (Cu, Mg, Fe) of α(Al) solution, ensures not only increase durability in ambient temperature, but also at elevated

temperature (250o

C), what due to it’s use in car industry is an advantage.

Superalloys show a good combination of mechanical strength and resistance to surface degradation under the influence of chemically

active environments at high temperature. They are characterized by very high heat and creep resistance. Their main application is in gas

turbines, chemical industry, and in all those cases where resistance to creep and the aggressive corrosion environment is required. Modern

jet engines could never come into use if not for progress in the development of superalloys. Superalloys are based on iron, nickel and

cobalt. The most common and the most interesting group includes superalloys based on nickel. They carry loads at temperatures well in

excess of the eighty percent of the melting point. This group includes the H282 alloy, whose nominal chemical composition is as follows

(wt%): Ni - base, Fe - max. 1.5%, Al - 1.5% Ti - 2.1%, C - 0.06% Co - 10% Cr - 20% Mo - 8.5%. This study shows the results of thermal

analysis of the H282 alloy performed on a cast step block with different wall thickness. Using the results of measurements, changes in the

temperature of H282 alloy during its solidification were determined, and the relationship dT / dt = f (t) was derived. The results of the

measurements taken at different points in the cast step block allowed identifying a number of thermal characteristics of the investigated

alloy and linking the size of the dendrites formed in a metal matrix (DAS) with the thermal effect of solidification. It was found that the

time of solidification prolonged from less than ome minute at 10 mm wall thickness to over seven minutes at the wall thickness of 44 mm

doubled the value of DAS.

The work determined the influence of aluminium in the amount from about 1% to about 7% on the graphite precipitates in cast iron with

relatively high silicon content (3.4% to 3.90%) and low manganese content (about 0.1%). The cast iron was spheroidized with cerium

mixture and graphitized with ferrosilicon. The performed treatment resulted in occurring of compact graphite precipitates, mainly nodular

and vermicular, of various size. The following parameters were determined: the area percentage occupied by graphite, perimeters of

graphite precipitates per unit area, and the number of graphite precipitates per unit area. The examinations were performed by means of

computer image analyser, taking into account four classes of shape factor. It was found that as the aluminium content in cast iron increases

from about 1.1% to about 3.4%, the number of graphite precipitates rises from about 700 to about 1000 per square mm. For higher

Al content (4.2% to 6.8%) this number falls within the range of 1300 – 1500 precipitates/mm2

. The degree of cast iron spheroidization

increases with an increase in aluminium content within the examined range, though when Al content exceeds about 2.8%, the area

occupied by graphite decreases. The average size of graphite precipitates is equal to 11-15 μm in cast iron containing aluminium in the

quantity from about 1.1% to about 3.4%, and for higher Al content it decreases to about 6 μm.

In the paper the results and analysis of abrasive wear studies were shown for two grades of cast steels: low-alloyed cast steel applied for

heavy machinery parts such as housing, covers etc. and chromium cast steels applied for kinetic nodes of pin-sleeve type. Studies were

performed using the modified in Department of Foundry pin-on-disc method.

The work presents the effect of strontium and antimony modification on the microstructure and mechanical properties of 226 silumin casts.

The performed research demonstrated that strontium causes high refinement of silicon precipitations in the eutectic present in the microstructure

of the examined silumin and it significantly affects the morphology of eutectic silicon from the lamellar to the fibrous one. Sr

modification also causes an increase of: the tensile strength „Rm” by 12%; the proof stress „Rp0,2” by 5%; the unit elongation „A” by 36%

and the hardness HB by 13%. Antimony did not cause a change in the microstructure of the silumin, yet it caused an increase in Rm and

HB by 5%, in Rp0,2 by 7% and in A by 4%.

The paper discusses possible applications of the percolation theory in analysis of the microstructure images of polycrystalline materials.

Until now, practical use of this theory in metallographic studies has been an almost unprecedented practice. Observation of structures so

intricate with the help of this tool is far from the current field of its application. Due to the complexity of the problem itself, modern

computer programmes related with the image processing and analysis have been used. To enable practical implementation of the task

previously established, an original software has been created. Based on cluster analysis, it is used for the determination of percolation

phenomena in the examined materials. For comparative testing, two two-phase materials composed of phases of the same type (ADI

matrix and duplex stainless steel) were chosen. Both materials have an austenitic - ferritic structure. The result of metallographic image

analysis using a proprietary PERKOLACJA.EXE computer programme was the determination of the content of individual phases within

the examined area and of the number of clusters formed by these phases. The outcome of the study is statistical information, which

explains and helps in better understanding of the planar images and real spatial arrangement of the examined material structure. The results

obtained are expected to assist future determination of the effect that the internal structure of two-phase materials may have on a

relationship between the spatial structure and mechanical properties.

The work is a continuation of research on the use of water mist cooling in order to increase efficiency of die-casting aluminum alloys using

multipoint water mist cooling system. The paper presents results of investigation on crystallization process and microstructure of synthetic

hypereutectic AlSi20 alloy. Casts were made in permanent mold cooled a with water mist stream. The study was conducted for unmodified

AlSi20 alloy and a modified one with phosphorus, titanium and boron on the research station allowing sequential multipoint cooling using

a dedicated program of computer control. The study demonstrated that the use of mold cooled with water mist stream and solution heat

treatment allows in wide range for the formation of the microstructure of hypereutectic silumins. It leads to the growth of microstructure

refinement and spheroidizing of phases in the casting.

In the paper the use of the artificial neural network to the control of the work of heat treating equipment for the long axisymmetric steel

elements with variable diameters is presented. It is assumed that the velocity of the heat source is modified in the process and is in real

time updated according to the current diameter. The measurement of the diameter is performed at a constant distance from the heat source

(∆z = 0). The main task of the model is control the assumed values of temperature at constant parameters of the heat source such as radius

and power. Therefore the parameter of the process controlled by the artificial neural network is the velocity of the heat source. The input

data of the network are the values of temperature and the radius of the heated element. The learning, testing and validation sets were

determined by using the equation of steady heat transfer process with a convective term. To verify the possibilities of the presented

algorithm, based on the solve of the unsteady heat conduction with finite element method, a numerical simulation is performed. The

calculations confirm the effectiveness of use of the presented solution, in order to obtain for example the constant depth of the heat

affected zone for the geometrically variable hardened axisymmetric objects.

The paper presents the results of investigations concerning the influence of negative (relative) pressure in the die cavity of high pressure

die casting machine on the porosity of castings made of AlSi9Cu3 alloy. Examinations were carried out for the VertaCast cold chamber

vertical pressure die casting machine equipped with a vacuum system. Experiments were performed for three values of the applied gauge

pressure: -0.3 bar, -0.5 bar, and -0.7 bar, at constant values of other technological parameters, selected during the formerly carried initial

experiments. Porosity of castings was assessed on the basis of microstructure observation and the density measurements performed by the

method of hydrostatic weighing. The performed investigation allowed to find out that – for the examined pressure range – the porosity of

castings decreases linearly with an increase in the absolute value of negative pressure applied to the die cavity. The negative pressure value

of -0.7 bar allows to produce castings exhibiting porosity value less than 1%. Large blowholes arisen probably by occlusion of gaseous

phase during the injection of metal into the die cavity, were found in castings produced at the negative pressure value of -0.3 bar. These

blowholes are placed mostly in regions of local thermal centres and often accompanied by the discontinuities in the form of interdendritic

shrinkage micro-porosity. It was concluded that the high quality AlSi9Cu3 alloy castings able to work in elevated temperatures can be

achieved for the absolute value of the negative pressure applied to the die cavity greater than 0.5 bar at the applied set of other parameters

of pressure die casting machine work.

The aging granulate is to activate the blowing agent during the manufacturing process to granulate models can re-expand and shape the

model of well-sintered granules, smooth surface and a suitable mechanical strength.

The article presents the results of studies which aim was to determine the optimum time for aging pre-foamed granules for pre-selected

raw materials.

The testing samples were shaped in an autoclave, with constant parameters sintering time and temperature. Samples were made at 30

minute intervals. Models have been subjected to flexural strength and hardness.

The investigation results of the influence of the reclaim additions on the properties of moulding sands with the GEOPOL geopolymer

binder developed by the SAND TEAM Company were presented. Two brands of hardeners were applied in the tested compositions, the

first one was developed by the SAND TEAM Company, marked SA72 and the new hardener offered by the KRATOS Company, marked

KR72. The main purpose of investigations was to determine the influence of reclaim fractions and the applied hardener on the basic

moulding sands properties, such as: bending and tensile strength, permeability and grindability. The unfavourable influence of the reclaim

additions into moulding sands on the tested properties as well as an increased hardening rate, were found. Moulding sands, in which the

hardener KR72 of the KRATOS Company was used, were less sensitive to the reclaim additions.

The paper concerns the problem of discontinuity in high pressure die castings (HPDC). The compactness of their structure is not perfect, as

it is sometimes believed. The discontinuities present in these castings are the porosity as follow: shrinkage and gas (hydrogen and gas-air

occlusions) origin. The mixed gas and shrinkage nature of porosity makes it difficult to identify and indicate the dominant source. The

selected parameters of metallurgical quality of AlSi9Cu3 alloy before and after refining and the gravity castings samples (as DI - density

index method), were tested and evaluated. This alloy was served to cast the test casting by HPDC method. The penetrating testing (PT) and

metallographic study of both kinds of castings were realized. The application of the NF&S simulation system allowed virtually to indicate

the porosity zones at risk of a particular type in gravity and high-pressure-die-castings. The comparing of these results with the experiment

allowed to conclude about NF&S models validation. The validity of hypotheses concerning the mechanisms of formation and development

of porosity in HPDC casting were also analyzed.