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1

Thermal Shock Resistance of Cast Iron with Various Shapes of Graphite Precipitates

100%

Jakubus A. , Soiński M. S.

Archives of Foundry Engineering

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2018

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tom Vol. 18, iss. 2

121--124

EN

The influence of a shape of graphite precipitates in cast iron on the thermal shock resistance of the alloy was initially determined. Investigations included the nodular cast iron and the vermicular one, as well as the cast iron containing flake graphite. The thermal shock resistance was examined at a special laboratory stand which allowed for multiple heating and cooling of specimens within the presumed temperature range. The specimens were inductively heated and then cooled in water of constant temperature of about 30°C. There were used flat specimens 70 mm long, 5 mm thick in the middle part, and tapering like a wedge over a distance of 15 mm towards both ends. The total length of cracks generated on the test surfaces of the wedge-shaped parts of specimens was measured as a characteristic value inversely proportional to the thermal shock resistance of a material. The specimens heated up to 500°C were subjected to 2000 test cycles of alternate heating and cooling, while the specimens heated up to 600°C underwent 1000 such cycles. It was found that as the heating temperature rose within the 500-600°C range, the thermal shock resistance decreased for all examined types of cast iron. The research study proved that the nodular cast iron exhibited the best thermal shock resistance, the vermicular cast iron got somewhat lower results, while the lowest thermal shock resistance was exhibited by grey cast iron containing flake graphite.

2

The Influence of Small Amounts of Aluminium on the Spheroidization of Cast Iron with Cerium Mischmetal

100%

Soiński M.

Archives of Foundry Engineering

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2012

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nr 2

3

Krytyczna ocena międzynarodowej znormalizowanej klasyfikacji cech wydzieleń grafitu w żeliwie

84%

Piaskowski J.

Odlewnictwo - Nauka i Praktyka

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2003

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tom R. 5, nr 5

38-50

4

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

84%

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

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tom 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.

5

Assessment of the Quality of Ductile Cast Iron EN-GJS-500-7 Through the Influence of its Chemical Composition on the Grain Composition of Spheroidal Graphite

84%

Pacha-Gołębiowska H.

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tom Vol. 22, iss. 4

85--89

EN

Quantitative evaluation of the microstructure obtained in a product is nowadays commonly required both in R&D activities and during routine quality control of materials and components. This paper presents an assessment of the quality of ductile cast iron, based on investigations of the effect of chemical composition on the distribution of ductile graphite precipitates in low-alloy cast iron EN-GJS-500-7. The size of graphite precipitates was expressed in terms of equivalent cross-sectional diameter, which made it possible to describe the distribution of graphite precipitates with a function simulating the log-normal distribution of graphite. The resulting U, W and Z parameters were statistically analysed, including the effect of chemical composition on graphite distribution. In the studied cast iron, the components that increase the U parameter are silicon, manganese and phosphorus, thus favourably affecting the total graphite number. In contrast, the constituents that decrease the U parameter are carbon, chromium and aluminium.

6

Effectiveness of cast iron vermicularization including 'conditioning' of the alloy

84%

Soiński M. S. , Mierzwa P.

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2011

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tom Vol. 11, iss. 2

133-138

EN

The performed investigations have resulted in conclusion that the vermicularizing treatment of 'basic' cast iron, consisting in 'conditioning' the alloy by means of VLCe(2) master alloy, introducing the DENODUL5 master alloy, and graphitizing with SRF75 master alloy, provides for obtaining vermicular graphite precipitates in the structure of material cast within 15 minutes' period from the modifying treatment. The cast iron has been melted in the induction crucible furnace of medium frequency under industrial conditions. The alloy has been subjected to vermicularization in the slender ladle of 1 Mg capacity. Graphitizing has been performed in the course of transferring the cast iron from the slender ladle to the pouring ladle. A series of test coupons in the form of reversed U-blocks of test part walls 25 mm thick have been cast of the produced cast iron. Then specimens both for metallographic examination and for testing the mechanical properties have been taken from the coupons. The analysis of cast iron structure has revealed, among others, that however purely vermicular graphite precipitates occurred in specimens taken out of the lower parts of test coupon walls (which are cooled faster), the nodular graphite precipitates in quantity up to 10% could be observed in specimens from the upper parts of test coupon walls (located close beneath the sinkhead).

7

The influence of small amounts of aluminium on the spheroidization of cast iron with cerium mischmetal

84%

Soiński M. S.

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tom Vol. 12, iss. 2

117-122

EN

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.

8

Struktura żeliwa nadeutektycznego modyfikowanego kompleksowo dodatkami zawierającymi bizmut i cer

67%

Warchala T. , Soiński M. S.

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tom T. 22, nr 2

145-157

PL

W artykule omówiono wyniki badań nad wpływem małych dodatków bizmutu (od 0,0006% do 0,0017%) i ceru (od 0,010% do 0,043%), wprowadzonych jako modyfikatory do żeliwa nadeutektycznego (Sc od 1,02 do 1,09), na charakterystyki grafitu oraz udział ferrytu w osnowie. Stwierdzono, że następuje zmniejszenie udziału grafitu, obwodu i liczby jego wydzieleń oraz zmiana postaci z płatkowej na zwartą. Udział ferrytu w osnowie wzrasta z udziału śladowego do ponad 80%. Optymalny pozimo zawartości bizmutu wynosi od 0,0007% do 0,0010%. Udział ceru powinien odpowiadać stosunkowi Ce/Bi w granicach 25-50.

EN

The paper discusses results of investigation concerning the influence of small additions of bismuth (from 0,0006% to 0,0017%) and cerium (from 0,010% to 0,043%) introduced as modifiers into the hypereutectic cast iron (Sc from 1,02 to 1,09) on the graphite characteristics and the fraction of ferrite in the matrix. Having performed the statistic analysis of experimental results, the authors have graphically determined the relationships between the bismuth and cerium content and the examined structure parameters. It has been found that the graphite percentage has decreased, as well as the total perimeter, the number of its precipitates, and the shape of graphite changes from flake to compact ones. The ferrite in the matrix increases from trace amounts to over 80%. It has been also noticed that for the hypereutectic cast iron the advantageous changes in the parameters of structure are related to the proportion of cerium to bismuth content. The optimum level of bismuth content falls within in range from 0,0007% to 0,0010%. The cerium should correspond to the Ce/Bi proportion equal to 25-50.