Study of the Processes of Shaping the Hollow Billets from Antifriction Alloys by the Centrifugal and Continuous Casting Methods
O. M. Khoroshylov$^{1}$, V. V. Kurylyak$^{2}$, O. S. Podolyak$^{1}$, N. S. Antonenko$^{1}$
$^1$Ukrainian Engineering and Pedagogical Academy, 16 Universytetska Str., UA-61003 Kharkiv, Ukraine
$^2$Ukrainian Institute of Arts and Science, 14 Instytutska Str., UA-08292 Bucha, Kyiv Region, Ukraine
Received: 21.05.2019; final version — 02.07.2019. Download: PDF
The focus of this work is a comparative analysis of the mechanisms of shaping of the hollow billets, which affect the yield of the centrifugal and continuous casting of БрО8Н4Ц2 (Cu–8% Sn–4% Ni–2% Zn)- and БрО5Ц5С5 (Cu–5% Sn–5% Zn–5% Pb)-type bronzes. As revealed, the action of centrifugal forces causes the segregation of chemical elements of the alloys, depending on their density. The alloying elements of the alloy, Sn and Pb, which have an increased density, contribute to this process more actively as compared with other elements. The factors affecting the intensity of the segregation process for alloying elements, the density of which is several times higher than the density of other alloy components, are determined. The causes of the appearance of tin, as an element with a maximum density, surrounded by the compounds with a minimum density are investigated. As established, the process of segregation occurring during the centrifugal casting reduces the uniform distribution of alloying elements throughout the billet bulk and significantly increases the allowances for machining. As shown, in the process of continuous casting, the force of gravity acts on the melt, but does not cause the separation of denser alloying elements during the shaping of the billet. As revealed, only one factor determining the amount of allowance for machining for the continuous casting process is the depth of the deformation hole on the outer surface of the billet, which is necessary to engage and remove the billet from the mould. The depth of the deformation hole is established, at which the shear stress of the cut corresponds to the shear stress on the cut for samples of the studied bronze grades. A three-dimensional model is constructed and proposed for determining the yield of suitable continuous casting of hollow billets depending on both the surface temperature of the billets and the forces acting on the billet from the side of the withdrawal-roll set. To assess the effect of technological parameters on the yield of the continuous and centrifugal casting processes, the web method is applied, which allows to expand the understanding of the various mechanisms of formation of billets. The study shows that, in comparison with the known indicators of the continuous-casting yield of 95.06–96.04% for billets with outside dimensions of 80–150 mm, one could increase the yield of casting up to 97.29–97.72%. It is concluded on the expedient fabrication of billets from antifriction alloys by continuous casting, since it allows increasing the yield of suitable casting by 22.35%–47.72% for the studied standard size of billets.
Keywords: centrifugal and continuous casting, cast billets, suitable casting yield, surface deformation hole.
DOI: https://doi.org/10.15407/ufm.20.03.367
Citation: O. M. Khoroshylov, V. V. Kurylyak, O. S. Podolyak, and N. S. Antonenko, Study of the Processes of Shaping the Hollow Billets from Antifriction Alloys by the Centrifugal and Continuous Casting Methods, Usp. Fiz. Met., 20, No. 3: 367–395 (2019); doi: 10.15407/ufm.20.03.367