"Cores are separate sand masses included in the mold to accomplish shapes that would be impossible or difficult to obtain with a normal simple mold cavity.
For example a core made for a pipe casting is expected, first, to support itself when placed in the mold and also withstand handling at room temperature. Second, it should withstand, for a short time, the high temperature of molten metal. Last, it should possess the ability, to completely lose its strength just after the metal around it has completely solidified.
Until recently cores for castings were made using oil bonded sands, with an oxidizable oil such as linseed oil acting as the bonding agent. With the discovery of sodium silicate solution as a binder for core sand, the process of core-making in the foundry industry has undergone a radical change. This process is referred to as the 'carbon dioxide-sodium silicate process' of core-making.
The main problem confronting the 'carbon dioxide-sodium silicate process' is the lack of collapsibility of the core when used at high temperatures.
The specific problem of promoting collapsibility in sodium silicate bonded cores has been studied by Mr. R. G. Liptai, who received his M.S. Degree in Mechanical Engineering in May, 1960. He tried various additives with a basic mix of sodium silicate solution and sand, and has obtained some very useful results.
In reviewing the work done by Mr, R. G. Liptai regarding the use of various additives in varying proportions, it has been found that three of the additives yielded satisfactory results throughout the entire temperature range from 1200°F - 1800°F, It was in this range that collapsibility of the sodium silicate bonded core was poorest. The three additives were calcium fluoride, magnesium oxide and magnesium carbonate.
The object of my thesis is to find out the most economical addition of magnesium carbonate to give the desired collapsibility in cores for different simulated pouring temperatures"--Introduction, pages 1-2.
Wolf, Robert V., 1929-1999
Miles, Aaron J.
Nowacki, C. Raymond
Scofield, Gordon L., 1925-1986
Mechanical and Aerospace Engineering
M.S. in Mechanical Engineering
Missouri School of Mines and Metallurgy
vi, 52 pages
© 1961 Wilfred Durairajan Paul, All rights reserved.
Thesis - Open Access
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Paul, Wilfred Durairajan, "An evaluation of the addition of magnesium carbonate to promote collapsibility in sodium silicate bonded cores" (1961). Masters Theses. 2783.