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Centrifugal Casting
is the preferred method of producing rotor end rings for A.C.
induction motors. O.E.M.s specify this manufacturing method for
optimum quality.
At Tallman We:
- Specialize in high conductivity grade centrifugally cast copper
as well as controlled conductivity grades.
- Can supply chrome copper when increased strength and high
conductivity is required.
- Can supply rotor end rings rough or finish machined to your
specifications.
- Meet the exacting standards of the major North American
O.E.M.s.
- Also supply to the rebuilt market.
- Furnish complete Quality Assurance documentation as required.
- Are competitive on both production and low volume requirements.
- Can offer expedited service normally at no extra charge for
breakdown requirements.
Improper Cooling Can Cause Lance
Tip Wear
 Port erosion is affected by the grain size of the copper. A
smaller grain size in the copper lance tip will assist in
minimizing the rate of port erosion. tallman's
fine
grain copper is produced by a proprietary process that does not
significantly reduce the thermal conductivity of the copper.
Copper oxides are concentrated along the grain boundaries. These
oxides when exposed to high concentrations of oxygen at elevated
temperatures, which occur when a lance tip is under-blown, will
react with the oxygen and cause cracks to form and propagate along
the grain boundaries.
A coarse grain structure that is typical of
a sand cast lance tip has less grain boundary area per square mm
and thus has a higher concentration of copper oxides along the
grain boundaries. This coarse grain structure leads to more severe
cracking and a faster rate of crack propagation.
A finer grain
structure that is typical of a centrifugal or forged lance tip
impedes crack propagation because of the number (density) and
shape of the grains.
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Difference between tallman's fine grain copper
(top photograph) and a
standard coarse grain sand cast copper (bottom photograph).
tallman centrifugal lance tip removed from service after 1163 heats (Steel Plant, India - September 2001)
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