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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.
EN
The work presents results of investigations concerning the production of cast iron containing about 5-6% aluminium, with the ferritic matrix in the as-cast state and nodular or vermicular graphite precipitates. The examined cast iron came from six melts produced under the laboratory conditions. It contained aluminium in the amount of 5.15% to 6.02% (carbon in the amount of 2.41% to 2.87%, silicon in the amount of 4.50% to 5.30%, and manganese in the amount of 0.12% to 0.14%). After its treatment with cerium mixture and graphitization with ferrosilicon (75% Si), only nodular and vermicular graphite precipitates were achieved in the examined cast iron. Moreover, it is possible to achieve the alloy of pure ferritic matrix, even after the spheroidizing treatment, when both the aluminium and the silicon occur in cast iron in amounts of about 5.2÷5.3%.
EN
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.
4
Content available Wear resistance of graphitized steels
EN
Heat-treated graphitized steels with different carbon, silicon and copper contents have been the object of study. The influence of the composition on the structure and wear resistance (weight loss of the specimen) of graphitized steels (after hardening and tempering) under the conditions of metal to metal dry sliding friction with the use of Amsler-type friction machines, has been investigated in this work. Research results have shown that the main factors affecting wear resistance of graphitized steels have been not only their metal base hardness, but the quantity, shape and distribution of graphite inclusions uniformity in the structure of such steels as well. A regression dependence of the quantity of specimen’s weight loss on carbon, silicon and copper content has been obtained in the work. The highest wear resistance was pertained by the steel having the following content: 1.60. . . 1.70%C; 2.20. . . 2.30%Si; 0.80. . . 0.90%Cu; 0.60. . . 0.70%Mn; 0.15. . . 0.18%Cr; 0.22. . . 0.25%Al; up to 0.015%S and 0.024%P.
PL
Przedmiotem badań była grafityzowana stal (po obróbce cieplnej) o zróżnicowanej zawartości węgla, krzemu oraz miedzi. W pracy przedstawiono wyniki badań wpływu składu chemicznego grafityzowanej stali, po hartowaniu i odpuszczaniu, na jej strukturę i zużycie ścierne (zmniejszenie masy próbki) w warunkach suchego tarcia ”metal-metal” na maszynie typu Amslera. Wyniki badań świadczą o tym, że odporność na zużycie ścierne zależy nie tylko od twardości osnowy metalowej, lecz także od ilości, kształtu i jednorodności wydzieleń grafitu oraz rozkładu przestrzennego wtrąceń w strukturze stali tego typu. Otrzymano zależności regresyjne wartości ubytku masy próbek w funkcji zawartości węgla, krzemu i miedzi. Największą odpornością na zużycie ścierne wyróżniają się stale o następującym składzie chemicznym: 1,60. . .1,70% C, 2,20. . . 2,30% Si, 0,80. . . 0,90% Cu, 0,60. . . 0,70% Mn, 0,15 . .. 0,18% Cr, 0,22. . . 0,25% Al, do 0,015% S i 0,024% P.
EN
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.
EN
The paper discusses the influence of aluminium in quantities from about 1.9% to about 4.7% on both the alloy matrix and the shape of graphite precipitates in cast iron spheroidized with cerium mixture (added in the quantity of 0.11%) and inoculated with ferrosilicon (1.29%). The metallographic examinations were carried out for specimens cut out of the wedge test castings (22 mm base width, 120 mm height, 180 mm length) halfway along their length. It was found that the highest susceptibility to graphitization exhibits the cast iron containing about 2.8% Al. The alloy matrices were classified and the degrees of graphite spheroidization were determined. Microscopic observations were carried out along the wedge test casting height at several places, the first distant by 20 mm from the specimen apex, the next ones every 20 mm farther. Precipitates of nodular and vermicular graphite were found in the cast iron structure. The results of examination allow to state that cast iron spheroidized in the way described here is characterised by the degree of spheroidization which increase with an increase in aluminium content within the examined range.
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
Content available remote Effectiveness of cast iron vermicularization including 'conditioning' of the alloy
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).
PL
W artykule przedstawiono badania nad oceną jakości żeliwa sferoidalnego w oparciu o analizę wielkości wydzieleń grafitu. Wytopy żeliwa sferoidalnego przeprowadzono w warunkach przemysłowych. Ocenę własności mechanicznych żeliwa przedstawiono w formie równań regresji.
EN
The paper describes the study of ductile cast iron for evaluation of quality. The investigations were carried out on the Powen S.A. Zabrze. The investigations determine a relationship between the area of graphite separations and mechanical properties.
PL
W artykule przedstawiono dane dotyczące wielkości wydzieleń grafitu izolowanego w żeliwie nadeutektycznym, modyfikowanym dodatkami zawierającymi bizmut oraz cer. Jako miarę wielkości wydzieleń przyjęto średnią średnicę wydzieleń izolowanych, będącą ilorazem obwodu wydzieleń i ich liczby. Stwierdzono niezbyt silny, ale istotny, dodatni wpływ bizmutu oraz znacznie silniejszy, złożony wpływ ceru. Średnia wielkość wydzieleń izolowanych grafitu w badanym żeliwie zmieniała się w przedziale od 8 žm do 20 žm.
EN
The paper presents some data regarding to the size of isolated graphite precipitates in hypereutectic cast iron modified with additions containing bismuth and cerium. The average diameter of isolated precipitates, being a total circumference length divided by the number of precipitates, have been assumed as the measure of the size of precipitates. A significant, though not very strong, positive influence of bismuth, and more complicated and much stronger influence of cerium have been observed. The average size of isolated graphite precipitates has varied within the range of 8-20 žm.
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.
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