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MICROSCOPIC VIEW OF IMPURITIES
Refractory cloth filters are designed to extract
dross, slag, refractory
particles, and nonmetallic inclusions from molten
metals. (RCF) were developed as a low-cost,high-efficiency alternative
to cellular ceramic and ceramic foam filtration systems. Made from
specially treated silica fibers, (RCF) are capable of withstanding pouring
temperatures ranging up to 3000'F (1620'C).(RCF) are ideal for inmold filtration
of gray, alleable,
white, compacted graphite, and ductile cast irons,
as well as non -ferrous aluminum and copper-based metal alloys. (RCF) are
available in rigid or
soft versions, in several mesh sizes, and can
be cut to any geo- metric
shape or size.(RCF) is also available in 20 mts.
long rolls. Inoculants or treatment alloys can be placed directly on the
active surface of (RCF) to simultaneously filter and metallurgically treat
the molten metal. |
| Silica cloth filters trap impurities by a different
means than mullite or alumina filters.When molten ferrous metal contacts
the RCF, special surface coatings decompose to form a continuous film of
fayalite (2Feo.SiO2). The fayalite coating is soft and sticky, at high
temperature, so that it entraps inclusions that contact it. Since this
sticky film forms instantly,even icron-sized inclusions are filtered out
of the very first metal to pass through the filter.
In magnesium treated ductile iron the fayalite
coating absorbs magnesium reaction products carried in the molten metal.
Low-melting solid solutions are formed on the surface of the silica fibers
to enhance removal of inclusions, especially magnesium dross, sulfides
and silicates formed from the nodularizing treatment.
Conventional hard-fired ceramic filters composed
of alumina or mullite cannot capture inclusions in this way because mullite
and alumina do not form the fayalite coating .(RCF)are especially effective
in removing fluid slags, such as manganese silicates,from molten metal
.RCF was developed by Ametek Haveg Division USA & we are the sole distributors
for India. |
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