Abstract
The paper presents the results of evaluation of the metallurgical quality
of master heat ingots and of the identification of non-metallic
inclusions (oxides of Al., Zr, Hf, Cr, etc.), which have been found in the
shrinkage cavities formed in these ingots. The inclusions
penetrate into the liquid alloy, and on pouring of mould are transferred to
the casting, especially when the filtering system is not
sufficiently effective. The specific nature of the melting process of nickel
and cobalt alloys, carried out in vacuum induction furnaces,
excludes the possibility of alloy refining and slag removal from the melt
surface. Therefore, to improve the quality of castings (parts of
aircraft engines), it is so important to evaluate the quality of ingots before
charging them into the crucible of an induction furnace. It has been
proved that one of the methods for rapid quality evaluation is an ATD
analysis of the sample solidification process, where samples are taken
from different areas of the master heat ingot. The evaluation is based on
a set of parameters plotted on the graph of the dT/dt derivative curve
during the last stage of the solidification process in a range from TEut
to Tsol.
Go to article