Metallurgy and Foundry Engineering
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ISSN 1230-2325
e-ISSN: 2300-8377
Issue Date
2005
Volume
Vol. 31
Number
No. 1
Description
Journal Volume
Metallurgy and Foundry Engineering
Vol. 31 (2005)
Projects
Pages
Articles
Solidification conditions of gray and white cast iron. Part I, Theoretical background
(2005) Fraś, Edward; Górny, Marcin; López, Hugo F.
The present work is based on a heat balance during the solidification of cast iron. Accordingly. an analytical expression was derived to relate the chilling tendency (CT) of cast iron with nucleation and growth processes associated with eutectic graphite and cementite constituents. A relationship is found between the CT and factors such as the physical-chemical state of liąuid, the distribution of nucleation sites, and the density of nucleation sites for eutectic grains. In particular, it is found that the casting modulus (M), enabling determinations of minimum wali thickness for chilled castings or chill widths in wedge shaped castings can be related to the CT. Finally, the present work provides a rationa-lization for the effect of technological factors such as the chemistry of the melt, inoculation practice. holding temperaturę and time on the resultant CT and chill of the cast iron.
Solidification conditions of gray and white cast iron. Part II, Experimental verification
(2005) Fraś, Edward; Górny, Marcin; López, Hugo F.
In this work, an experimental verification of the theoretical principles for the transition from gray to mottled and white cast iron solidification is presented. Experimental tests have been implemen-ted using plate and wedge shaped castings of various sizes. The experiments included inoculated and non-inoculated cast irons of different chemical compositions and time after the inoculation treatment. In addition, thermal analysis tests were employed to determine the degree of undercooling of graphite eutectic ATm. This included microstructural evaluations in order to establish the density of eutectic grain (cells). This procedurę enabled the calculation of the theoretical grain density (celi count) TV, the wedge value w, as well as the chilling tendency CT of cast iron. It was found that the predictions of the theoretical analysis are in good agreement with the experimental outcome for the chill exhibited in wedge and plate shaped castings.
Determining optimum volume of cold and hot blast air in single-row coke cupolas
(2005) Khatemi, Belkheir; Longa, Władysław
In this study a formuła was derived to calculate optimum volume of cupola blast air [m /(m -s). standard operating conditions], cold or hot, for single-row coke cupolas, assuming that the lower boun-dary of the melting zone is adhacent to the upper boundary of the combustion zone (the condition of optimum cupola running formulated by A. Achenbach in 1931). Relevant eąuations and tables have also been developed to make the calculations easier. From computations madę in this study it follows that the optimum blast air volume is increasing with an increase of the blast air temperaturę, assuming for cold blast a value close to 100 m /(m -min) (Buzek postulate), with modulus of the metallic charge lumps changing in a rangę of 15 to 20 mm.
Oxygen-blowing remelts of low-alloyed Cr-Mn-Ni-Mo steels with the variable oxidation rate of carbon, chromium and phosphorus
(2005) Sobula, Sebastian; Głownia, Jan
Low-alloy Cr-Mn-Ni-Mo cast steels and high-alloy manganese cast steels are freąuently use as castings in such areas as minerał industry and power industry. Melting technology of these steels is often based on the use the return-scrap in charge, because the prices of nickel and molybdenum are very high. Basic electric arc furnaces were used in the oxidation re-melting of high manganese and Iow alloyed Cr-Mn-Ni-Mo steel scraps. The measuring of bath temperaturę and chemical composition were realized for control of C, P and Cr oxidation rates. This article shows effect of two methods of carbon boil, used in re-melting technology: first is carbon oxydation by iron ore and second is oxygen-blo-wing. The results of these measurements showed that at the oxygen blowing under the pressure of ca 0,6-K),8 MPa and oxygen capacity of 0,37-^0,60 N-m /(min-Mg), the average value of decarburisation ratę is 1,03-^2,08% C/h, according the temperaturę of the bath. In the same condition of oxidation, the dephosphorisation ratę in Cr-Mn-Ni-Mo is 0-K),12% P/h. It was shown that the temperatures above 1620°C protected steel bath against high chromium losses. At these temperatures the average value of phosphor oxidation ratę is 0,070% P/hour.
Determination of the surface tension for binary ionic solutions by means of Butler model
(2005) Iwanciw, Jerzy; Kalicka, Zofia Bronisława; Kawecka-Cebula, Elżbieta; Pytel, Krzysztof
It was attempted in this work to study the applicability of Butler approach to the metal oxide solutions. First of all, the authors tried to determine the impact of the thermodynamic activity coeffi-cients of the components of the bulk phase on the surface tension. The activity coefficients series expansions reported by Ban-ya and one of the authors of this work were used. The model eąuations were solved by means of a Newton regression method, which allowed to calculate the components contents in the surface phase. Those contents were subseąuently substituted into the modified Butler master eąuation, which gave desired finał surface tensions estimates for the considered oxide binaries. The computations were done for liquidMnO-SiO2 system (at 1843 K and 1990 K) and subseąuently for MnO-Al2O3 (at 2058 K) and MnO-CaO (at 2473 K) systems. For MnO-SiO2 system at 1843 K, theobtained results could be compared to the experimental ones and a fairly good agreement was found. For MnO-Al2O3 and MnO-CaO systems, unfortunately, there is no experimentally measured surface tension data, therefore it was not possible to make any comparison. Nevertheless, the model may be ąuite useful for the surface tension estimates for the systems, which have not been yet investigated and such model calculations like presented in this work may provide acceptable predictions.