TESTING CALCIA-BASED REFRACTORIES FOR RESISTANCE
TO NONFERROUS MOLTEN METALS
A. V. Gropyanov,
L. B. Tsimbulov,
and L. Sh. Tsemekhman
Translated from Novye Ogneupory, No. 6, pp. 29 – 34, October, 2002.
Refractory crucibles made of calcium oxide are tested for resistance to molten copper, nickel, cobalt, and slag.
A refractory based on CaO and a ceramic bond does not enter into chemical reaction with molten copper,
nickel, and cobalt; however, it does react with impurities contained in it such as oxides of copper, nickel, and
cobalt. Calcium oxide is shown to exert a refining effect on the molten metals.
The unique properties of calcium oxide (calcia) manifest
themselves not only in their resistance to high temperature,
but also in the ability to refine the molten metal from oxides
of aluminum, silicon, sulfur, phosphorus, nitrogen, and other
impurities. In a patent claim [No. 63-28869, Japan], a
method for manufacture of high-purity alloys based on iron,
nickel, and cobalt with the addition of aluminum or an alumi-
num alloy has been presented in which CaO crucibles in a
non-oxidizing medium or vacuum were used. The material of
the crucible contained 15 to 75% free calcia and, in the corre-
sponding proportion, magnesium oxide. By this procedure,
the molten metal was made completely free of sulfur, phos
phorus, oxygen, and nitrogen; however, residual calcium
(up to 0.02%) and residual magnesium (up to 0.03%) were
found in the melt.
U.S. patent No. 5102450 concerns the use of CaO-based
crucibles for melting titanium doped with niobium, tantalum,
tungsten, and molybdenum. During the melting of the metal,
a decrease in the concentration of oxygen, sulfur, and nitro
gen in the melt was clearly observed.
In U.S. patents Nos. 4710481 and 5045406 and in ,
methods for melting titanium and titanium-chromium and ti
tanium-tantalum alloys using a calcia crucible have been de
scribed. Calcium oxide was shown to produce a refining ef
fect on the melt.
In Japanese patent No. 4710481 a method for manufac
ture of high-grade titanium and titanium alloys using a high-
purity CaO crucible has been described. The composition of
the crucible material was: CaO, not less than 99 wt.%; SiO
not higher than 0.1 wt.%; Fe
, not higher than 0.02 wt.%;
other impurities, not higher than 0.5 wt.%.
In U.S. patent No. 4999053 methods for treating molten
metals for impurities using a CaO-based lining have been
considered. Pictorially, the refining effect of a CaO-contain-
ing lining on molten steel is demonstrated in Figs. 1 and 2.
To show the technological advantages of a calcia-based
refractory containing a 90% minimum of free CaO (reco-
vered from a deposit of intrinsically pure chalk in Russia),
the refractory material was tested for resistance to molten
nonferrous metals and slag. Chalk from the Latnenskoe de-
Refractories and Industrial Ceramics Vol. 44, No. 1, 2003
1083-4877/03/4401-0046$25.00 © 2003 Plenum Publishing Corporation
St. Petersburg Institutes for Refractory Material Joint-Stock Co.,
St. Petersburg; Gipronikel’ Research Institute, Russia.
log [S] [S]
01 2 34 5 7 10
Fig. 1. Pictorial interpretation of the process of steel desulfurization
using a calcia-periclase lining refractory. Numerals at solid curves
indicate MgO concentration, %; a dashed line refers to the calcia re