LLC “RUSAL Engineering-Technical Center”, Krasnoyarsk, Russia:

А. А. Ilin, Team Leader
S. V. Soldatov, Manager

Siberian Federal University, Krasnoyarsk, Russia:
N. V. Belousova, Professor, Head of the Department of Non-Ferrous Metallurgy, e-mail: netmamba@mail.ru

In order to determine and minimise the number of such casting defects as shrinkage porosity in the body of a casting, casting and crystallization of a small aluminium ingot have been simulated. The hydrodynamic problem of alloy casting in the mould was calculated with the help of ProCAST and the overlaid grids. The standard А356 alloy was used as the ingot material, while the mould was made of grey iron (SCh20). A thermodynamic database was used to calculate the temperature effect on heat conductivity, density, dynamic viscosity and the ratio between the solid and liquid phases of that particular alloy. To solve this problem, a work model was built of a mould with an ingot. A finite element tetragonal mesh was created in the Mesh_Cast module. The mesh included 2,012,845 finite elements. It was found that the use of special reflecting barriers to minimise heat dissipation during crystallization didn’t prove to be effective. Modification of the mould, i.e. making the bottom of the mould thicker to increase its accumulative capacity and prevent solidification of the lower layers of metal, failed to yield any positive result. A 10 mm rise in the bottom padding leads to a 10–15% reduction in porosity in the surface padding area. However, it didn’t produce any noticeable effect on the shrinkage porosity in the casting body. Bigger slots inside the mould help split the porosity zone pushing it towards the ends of the mould and redistributing it in the horizontal plane. The use of cooling fins at the bottom of the mould leads to some redistribution of the porosity zone both vertically and horizontally. However, this design doesn’t appear to make a huge difference. The most acceptable porosity in the casting body can be achieved with the Befesa mould which has a stepped design.

1. Kobyakov K. V., Nikolaychuk Yu. A. Simulating the formation of shrinkage defects in castings. Lite i Metallurgiya. 2014. No. 4. pp. 131–137.
2. Santhi S. Calculation of shrinkage of sand cast aluminium alloys. International Journal of Applied Engineering Research. 2018. Vol. 13, No. 11. pp. 8889–8893.
3. Jabur A. S., Kushnaw F. M. Casting simulation and prediction of shrinkage cavities. Journal of Applied & Computational Mathematics. 2017. Vol. 6, No. 4.
4. Grandfield J. F. Remelt ingot production technology. Light Metals. 2009. Vol. 3. pp. 1003–1010.
5. Ho K., Pehlke R. D. Mechanisms of heat transfer at a metal-mold interface. AFS Transactions. 1984. Vol. 92. pp. 587–598.
6. Li K.-D., Chang E. A mechanism of porosity distribution in A356 aluminum alloy castings. Materials Transactions. 2002. Vol. 43, No. 7. pp. 1711–1715.
7. Kulikov D. Yu., Voronin Yu. F., Kamaev V. A., Matokhina A. V. Quality analysis system for minimising casting rejection rate. Vestnik kompyuternykh i informatsionnykh tekhnologiy. 2008. No. 4. pp. 33–35.
8. Zherdev A. S., Vinogradov D. A., Tretiakov Ya. A., Ilyin A. A., Klyuchantsev A. B. Understanding the effect of water cooling in a mould during crystallization of aluminium alloy ingots. Rasplavy. 2015. No. 6. pp. 86–94.
9. Devyatov S. V. ProCast — Virtual modelling of the casting technology. CADMaster. 2006. No. 5. pp. 36–43.
10. Riedler M., Michelic S., Bernhard C. Formation of shrinkage porosity during solidification of steel: Numerical simulation and experimental validation. IOP Conference Series: Materials Science and Engineering. 2016. Vol. 143, No. 1. p. 012035.
11. Fu J., Wang K. Modelling and simulation of die casting process of A356 semi-solid alloy. Procedia Engineering. 2014. Vol. 81. pp. 1565–1570.
12. Grandfield J., Cleary P., Prakash M., Sinnott M., Oswald K., Nguyen V. Mathematical modelling of ingot caster filling systems. Proceedings of 8^th Aluminium Cast House Technology Conference: Minerals, Metals and Materials Society 2003. Brisbane, Australia, 2003. pp. 271–276.