The article presents results of pitting corrosion studies of selected silicon cast irons. The range of studies included low, medium and high
silicon cast iron. The amount of alloying addition (Si) in examined cast irons was between 5 to 25 %. Experimental melts of silicon cast
irons [1-3] were conducted in Department of Foundry of Silesian University of Technology in Gliwice and pitting corrosion resistance
tests were performed in Faculty of Biomedical Engineering in Department of Biomaterials and Medical Devices Engineering of Silesian
University of Technology in Zabrze. In tests of corrosion resistance the potentiostat VoltaLab PGP201 was used. Results obtained in those
research complement the knowledge about the corrosion resistance of iron alloys with carbon containing Si alloying addition above 17 %
[4-6]. Obtained results were supplemented with metallographic examinations using scanning electron microscopy. The analysis of
chemical composition for cast irons using Leco spectrometer was done and the content of alloying element (silicon) was also determined
using the gravimetric method in the laboratory of the Institute of Welding in Gliwice. The compounds of microstructure were identify by
X-ray diffraction.
The results of studies on the use of magnesium alloy in modern Tundish for production of vermicular graphite cast irons were described. This paper describes the results of using a low-magnesium ferrosilicon alloy for the production of vermicular graphite cast irons. The paper presents a vermicular (and nodular) graphite in different walled castings. The results of trials have shown that the magnesium Tundish process can produce high quality vermicular graphite irons under the specific industrial conditions of Foundries - Odlewnie Polskie S.A. in Starachowice. In this work describes too preliminary studies on the oxygen state in cast iron and their effect on graphite crystallization.
The paper presents the issue of synthetic cast iron production in the electric induction furnace exclusively on the steel scrap base. Silicon
carbide and synthetic graphite were used as carburizers. The carburizers were introduced with solid charge or added on the liquid metal
surface. The chemical analysis of the produced cast iron, the carburization efficiency and microstructure features were presented in the
paper. It was stated that ferrosilicon can be replaced by silicon carbide during the synthetic cast iron melting process. However, due to its
chemical composition (30% C and 70% Si) which causes significant silicon content in iron increase, the carbon deficit can be partly
compensated by the carburizer introduction. Moreover it was shown that the best carbon and silicon assimilation rate is obtained where the
silicon carbide is being introduced together with solid charge. When it is thrown onto liquid alloy surface the efficiency of the process is
almost two times less and the melting process lasts dozen minutes long. The microstructure of the cast iron produced with the silicon
carbide shows more bulky graphite flakes than inside the microstructure of cast iron produced on the pig iron base.
The paper proposes a methodology useful in verification of results of dilatometric tests aimed at determination of temperatures defining
the start and the end of eutectoid transformation in the course of ductile cast iron cooling, based on quenching techniques and
metallographic examination. For an industrial melt of ductile cast iron, the effect of the rate of cooling after austenitization at temperature
900°C carried out for 30 minutes on temperatures TAr1
start and TAr1
end was determined. The heating rates applied in the study were the
same as the cooling rates and equaled 30, 60, 90, 150, and 300°C/h. It has been found that with increasing cooling rate, values of
temperatures TAr1
start and TAr1
end decrease by several dozen degrees.
The publication presents the results of examination of selected carburizers used for cast iron production with respect to their electric
resistance. Both the synthetic graphite carburizers and petroleum coke (petcoke) carburizers of various chemical composition were
compared. The relationships between electrical resistance of tested carburizers and their quality were found. The graphite carburizers
exhibited much better conductivity than the petcoke ones. Resistance characteristics were different for the different types of carburizers.
The measurements were performed according to the authors’ own method based on recording the electric current flow through the
compressed samples. The samples of the specified diameter were put under pressure of the gradually increased value (10, 20, 50, 60, and
finally 70 bar), each time the corresponding value of electric resistance being measured with a gauge of high accuracy, equal to 0.1μΩ.
The higher pressure values resulted in the lower values of resistance. The relation between both the thermal conductance and the electrical
conductance (or the resistance) is well known and mentioned in the professional literature. The results were analysed and presented both in
tabular and, additionally, in graphic form.
The work determined the influence of aluminium in the amount from about 0.6% to about 8% on graphitization of cast iron with
relatively high silicon content (3.4%-3.9%) and low manganese content (about 0.1%). The cast iron was spheroidized with cerium mixture
and graphitized with ferrosilicon. It was found that the degree of graphitization increases with an increase in aluminium content in cast
iron up to 2.8%, then decreases. Nodular and vermicular graphite precipitates were found after the applied treatment in cast iron containing
aluminium in the amount from about 1.9% to about 8%. The Fe3AlCx carbides, increasing brittleness and deteriorating the machinability of
cast iron, were not found in cast iron containing up to about 6.8% Al. These carbides were revealed only in cast iron containing about 8% Al.
The paper presents an analysis of factors affecting the wear of cylinder liners. The effect of the graphite precipitation morphology on the
cylinder liner wear mechanism is presented. Materials used to cast cylinder liners mounted in a number of engines have been examined for
their conformity with requirements set out in applicable Polish industrial standard. A casting for a prototype cylinder liner has been made
with a microstructure guaranteeing good service properties of the part.
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.
The influence of aluminium (added in quantity from about 0.6% to about 2.8%) on both the alloy matrix and the shape of graphite precipitates in cast iron treated with a fixed amounts of cerium mischmetal (0.11%) and ferrosilicon (1.29%) is discussed in the paper. The metallographic examinations were carried out for specimens cut out of the separately cast rods of 20 mm diameter. It was found that the addition of aluminium in the amounts from about 0.6% to about 1.1% to the cast iron containing about 3% of carbon, about 3.7% of silicon (after graphitizing modification), and 0.1% of manganese leads to the occurrence of the ferrite-pearlite matrix containing cementite precipitates in the case of the treatment of the alloy with cerium mischmetal . The increase in the quantity of aluminium up to about 1.9% or up to about 2.8% results either in purely ferrite matrix in this first case or in ferrite matrix containing small amounts of pearlite in the latter one. Nodular graphite precipitates occurred only in cast iron containing 1.9% or 2.8% of aluminium, and the greater aluminium content resulted in the higher degree of graphite spheroidization. The noticeable amount of vermicular graphite precipitates accompanied the nodular graphite.
The influence of aluminium added in amounts of about 1.6%, 2.1%, or 2.8% on the effectiveness of cast iron spheroidization
with magnesium was determined. The cast iron was melted and treated with FeSiMg7 master alloy under industrial conditions.
The metallographic examinations were performed for the separately cast rods of 20 mm diameter. They included the assessment of the
shape of graphite precipitates and of the matrix structure. The results allowed to state that the despheroidizing influence of aluminium
(introduced in the above mentioned quantities) is the stronger, the higher is the aluminium content in the alloy. The results of examinations
carried out by means of a computer image analyser enabled the quantitative assessment of the considered aluminium addition influence.
It was found that the despheroidizing influence of aluminium (up to about 2.8%) yields the crystallization of either the deformed nodular
graphite precipitates or vermicular graphite precipitates. None of the examined specimens, however, contained the flake graphite
precipitates. The results of examinations confirmed the already known opinion that aluminium widens the range of ferrite crystallization.
The present paper is a presentation of results of a study on morphology, chemical composition, material properties (HVIT, HIT, EIT), and nanoindentation elastic and plastic work for carbide precipitates in chromium cast iron containing 24% Cr. It has been found that the carbides differ in chemical composition, as well as in morphology and values characterizing their material properties. The carbides containing the most chromium which had the shape of thick and long needles were characterized with highest values of the analyzed material properties.
An initial assessment of the effectiveness of cast iron inoculation, performed by the method of impulse introducing the master alloy into
cast iron, is presented. The experiment was concerned with the hypoeutectic gray cast iron inoculated with either the Alinoc or the Barinoc
master alloy by means of an experimental device for pneumatic transportation. Examinations involved pneumatic injection of the
powdered inoculant carried in a stream of gaseous medium (argon) into the metal bath held in the crucible of an induction furnace. It was
found that the examined process is characterised by both high effectiveness and stability.
The paper presents results of examination of material parameters of cast iron with structure obtained under rapid resolidification conditions carried out by means of the nanoindentation method.
A cast iron is gradient material. This means that depending on the cooling rate it is possible, at the same chemical composition and the physicochemical state of molten metal, to obtain material with a different structure. The connection between the wall thickness of the casting and the speed of its cooling expresses the casting module. Along with the module escalation a cooling rate of the casting is reducing what can cause changes of the microstructure and the increased tendency to the crystallization of distorted graphite forms. Inspections of experimental castings from nodular cast iron with different modules were conducted to the graphite form.
The paper presents influence of soaking parameters (temperature and time) on structure and mechanical properties of spheroidal graphite
nickel-manganese-copper cast iron, containing: 7.2% Ni, 2.6% Mn and 2.4% Cu. Raw castings showed austenitic structure and relatively
low hardness (150 HBW) guaranteeing their good machinability. Heat treatment consisted in soaking the castings within 400 to 600°C for
2 to 10 hours followed by air-cooling. In most cases, soaking caused changes in structure and, in consequence, an increase of hardness in
comparison to raw castings. The highest hardness and tensile strength was obtained after soaking at 550°C for 6 hours. At the same time,
decrease of the parameters related to plasticity of cast iron (elongation and impact strength) was observed. This resulted from the fact that,
in these conditions, the largest fraction of fine-acicular ferrite with relatively high hardness (490 HV0.1) was created in the matrix. At
lower temperatures and after shorter soaking times, hardness and tensile strength were lower because of smaller degree of austenite
transformation. At higher temperatures and after longer soaking times, fine-dispersive ferrite was produced. That resulted in slightly lower
material hardness.
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.
Determined were direction and intensity of influence of alloying additions on the number of eutectic graphite colonies in austenitic cast iron Ni-Mn-Cu. Chemical composition of the cast iron was 1.7 to 3.3% C, 1.4 to 3.1% Si, 2.8 to 9.9% Ni, 0.4 to 7.7% Mn, 0 to 4.6% Cu, 0.14 to 0.16% P and 0.03 to 0.04% S. Analysed were structures of mottled (20 castings) and grey (20 castings) cast iron. Obtained were regression equations determining influence intensity of individual components on the number of graphite colonies per 1 cm2 (LK). It was found that, in spite of high total content of alloying elements in the examined cast iron, the element that mainly decides the LK value is carbon, like in a plain cast iron.
In the paper, a relationship between chemical composition of Ni-Mn-Cu cast iron and its structure, hardness and corrosion resistance is
determined. The examinations showed a decrease of thermodynamic stability of austenite together with decreasing nickel equivalent value,
in cast iron solidifying according to both the stable and the metastable systems. As a result of increasing degree of austenite
transformation, the created martensite caused a significant hardness increase, accompanied by small decline of corrosion resistance. It was
found at the same time that solidification way of the alloy and its matrix structure affect corrosion resista