Journal of Casting & Materials Engineering
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ISSN 2543-9901
Issue Date
2021
Volume
Vol. 5
Number
No. 4
Description
Journal Volume
Journal of Casting & Materials Engineering
Vol. 5 (2021)
Projects
Pages
Articles
Derivation of equations for a size distribution of spherical particles in non-transparent materials
(AGH University of Science and Technology Press, 2021) Gurgul, Daniel; Burbelko, Andriy A.; Wiktor, Tomasz
This paper presents a new proposition on how to derive mathematical formulas that describe an unknown Probability Density Function (PDF$_{3}$) of the spherical radii ($r_{3}$) of particles randomly placed in non-transparent materials. We have presented two attempts here, both of which are based on data collected from a random planar cross-section passed through space containing three-dimensional nodules. The first attempt uses a Probability Density Function (PDF$_{2}$) the form of which is experimentally obtained on the basis of a set containing two-dimensional radii ($r_{2}$). These radii are produced by an intersection of the space by a random plane. In turn, the second solution also uses an experimentally obtained Probability Density Function (PDF$_{1}$). But the form of PDF$_{1}$ has been created on the basis of a set containing chord lengths collected from a cross-section. The most important finding presented in this paper is the conclusion that if the PDF$_{1}$ has proportional scopes, the PDF$_{3}$ must have a constant value in these scopes. This fact allows stating that there are no nodules in the sample space that have particular radii belonging to the proportional ranges the PDF1.
A morphological characterization of high yield chitin from periwinkle shells
(AGH University of Science and Technology Press, 2021) Chiosa Odili, Cletus; Gbenebor, Oluwashina Philips; Haffner, Henry Adekola; Adeosun, Samson Oluropo
Research on obtaining chitin from periwinkle shell is scarce due to the very low yield of chitin from this kind of shell. This study reports a method of processing periwinkle shells to obtain high yield, bio-medically suitable chitin. The experiment was designed using IM and 2M concentrations of HCl for demineralization and a 1M NaOH concentration for deproteinization. FTIR, SEM, XRD and DTA analytical tools were used to characterize the extracted chitin. The FTIR spectral, XRD patterns and SEM analysis, revealed the complete removal of calcium carbonate by the acid concentrations used. The particle-like form of periwinkle shell was transformed to sheet-like fiber and globular-like fiber of $\alpha$-chitin by increasing the concentration of HCl from1M to 2M respectively. The crystal size increased from 11.2Ǻ (1M HCl) to 13.4Ǻ (2M HCl). The yield of chitin from periwinkle shell also increased from 52% to 71% using 1M and 2M HCl respectively. Thus, acid concentrations can be used to alter the structure of chitin with different mechanical properties.
Interaction of N with white-solidified cast iron model alloys - the effect of Mn and Cu on the formation of Fe and Si nitrides
(AGH University of Science and Technology Press, 2021) Kante, Stefan; Leineweber, Andreas
Surface remelting and subsequent nitriding improves the surface properties of cast irons. Upon remelting, a white-solidified surface layer forms, which contains coarse Si-free eutectic cementite ($\theta$) and Si-enriched ferrite, pearlite or martensite in the intercarbidic regions between the eutectic $\theta$. Nitriding produces a compound layer at the surface, which is composed of $\epsilon$ and $\gamma \prime$-iron (carbo)nitrides and enhances the corrosion resistance. Nitriding of white-solidified Fe-C-Si alloys, being model materials for remelted low-alloy ferritic cast irons, has shown that Si dissolved in $\alpha$-Fe notably affects the formation of $\epsilon$ and $\gamma \prime$ in intercarbidic regions while Si simultaneously precipitates as amorphous nitride, X. Under process conditions only allowing for the formation of $\gamma \prime$ in pure Fe, Si dissolved in $\alpha$-Fe promotes the formation of $\epsilon$ over the formation $\gamma \prime$, whereas Si-free eutectic $\theta$ transforms into nitride following the sequence $\theta \to \epsilon \to \gamma \prime$. The present work studies the nitriding of white-solidified Fe-3.5wt.%C-3wt.%-M alloys with additions of M = 1 wt.% Mn, 1 wt.% Cu or 1 wt.% Mn + 1 wt.% Cu, serving as model materials for remelted pearlitic cast irons. The presence of Mn and/or Cu causes notable deviations from the nitriding behavior known from Fe-C-Si alloys. Mn accelerates the precipitation of X in intercarbidic regions and obstructs the transformation of $\epsilon$ formed from Si-free $\theta$ into $\gamma \prime$. Cu promotes the formation of $\gamma \prime$ in Si-rich intercarbidic regions, surpassing the $\epsilon$-promoting effect of Si.
Scaling behaviour of Si-alloyed steel slabs under reheating conditions
(AGH University of Science and Technology Press, 2021) Mikl, Gregor; Höfler, Thomas; Gierl-Mayer, Christian; Danninger, Herbert; Linder, Bernhard; Angeli, Gerhard
Reheating of steel slabs for further processing such as hot rolling usually takes place in gas-fired pusher furnaces. Temperatures well above 1000°C, combined with an atmosphere containing $H_{2}O$, $CO_{2}$, and $O_{2}$, lead to substantial oxidation of most steel grades. Newly developed advanced steels often contain significant amounts of Si. This element plays a dominant role in the scaling behaviour near the steel-scale-interface, since fayalite $(Fe_{2}SiO_{4})$ forms a eutectic with wuestite $(Fe_{1-x}O)$ that melts as low as 1177°C. To better understand the high temperature oxidation behaviour, lab-scale trials were performed with different steel grades containing up to 3 wt.% Si. Possible interactions of Si with other alloying elements present in the samples such as Cr, Mn and Al were also of interest. The atmosphere contained 20% $H_{2}O$, 7% $CO_{2}$, and 3% $O_{2}$, resembling reheating conditions in pusher furnaces, and temperatures ranged from 1100 to 1240°C. For metallographic investigation, the oxidised samples were cold mounted under vacuum using taper section angles. After preparation, the sections were examined through light microscopy, SEM/EDS, XRD, and TEM. The local distribution of the alloying elements could be mapped efficiently, and phase identification was successful in most parts. Under the applied experimental conditions, the elements of interest were present in their oxidic form either as pure or as mixed oxides. Higher Si-contents led to an increased build-up of eutectic melting phase at the steel-scale-interface at temperatures above 1177°C, which in turn further accelerated the oxidation.
Numerical analysis of the influence of the modification of the ladle shroud on fluid flow behavior in a one-strand tundish during continuous steel casting
(AGH University of Science and Technology Press, 2021) Suchan, Hanna; Cwudziński, Adam
A tundish is a device from which liquid steel is pour into a mold. Therefore tundish hydrodynamic conditions have a significant impact on solidification during continuous steel casting (CSC) process. Modification of ladle shroud workspace, allows for the modification of liquid steel movement in the tundish. In the following work, numerical simulations were performed which allowed the impact of the modification of the ladle shroud workspace on the liquid steel flow structure in a one-strand tundish to be determined. In order to assess the impact of the modification of the ladle shroud on the behavior of the liquid steel in the tundish, simulations were performed, on the basis of which the percentage share of stagnant, ideal mixing and plug flow zones were determined. In addition, the mixing parameters were determined, allowing the estimation of casting duration during sequential casting. The flow fields of liquid steel for each modification of the ladle shroud were performed. The average velocity of liquid steel flowing through the tundish, the Reynolds number and turbulent intensity were also described. The obtained results showed, among others, that the application of three cylinders with a diameter of 0.041 m into the ladle shroud with a diameter of 0.11 m increases the share of active flow in the tundish in relation to the tundish with Conventional Ladle Shroud. At the same time, applying a ladle shroud with a diameter of 0.11 m during casting is the most favorable in relation to the hydrodynamics of the tundish.