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Are
all tungsten alloys inherently brittle?
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No. This
misunderstanding comes largely from experiences
with pure tungsten in the recrystallized state.
Tungsten heavy alloy has a totally different,
rounded grain structure that provides good
machining behavior and the ability of some
alloys to be stretched by 30% of their initial
length without fracture.(close) |
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Is
tungsten one of those rare metals that could
be in short supply? |
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While the
element tungsten isn't as well known as other
commercial metals, its geological abundance
is roughly that of copper or tin. This means
tungsten will be available for new and existing
applications for a long time to come.(close) |
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Is
tungsten heavy alloy similar to tungsten carbide?
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While both
families of materials are made by the powder
metallurgy process of liquid phase sintering
and are both very rigid, many differences
exist. Tungsten carbide provides high hardness
and wear resistance, whereas tungsten heavy
alloy gives both ductility and higher density.
The two families are not interchangeable.(close) |
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Why
is depleted uranium (DU) being replaced by
tungsten alloys in many applications?
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Tungsten
heavy alloys provide high material densities
comparable to DU without the inherent radioactivity,
toxicity, and high chemical reactivity of
the latter. This simplifies life cycle considerations
for many components.(close) |
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Can
tungsten heavy alloy be cast like most metals?
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No. Due
to the extremely high melting point of tungsten,
it is not feasible to melt and cast alloys
containing the high percentages of tungsten
needed to achieve the density range of interest.
Rather, energy and material conservative powder
metallurgy techniques are used to produce
fully dense metal shapes. (close) |
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Why
is tungsten so much more expensive than lead?
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The significantly
higher cost of tungsten results from the higher
cost of the mined ore as well as the more
complicated processing steps needed to get
to the metallic state. While costing more,
tungsten provides a number of benefits over
lead - including both material performance
and environmental factors.(close) |
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Is
solid state sintered tungsten heavy alloy
available? |
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Yes. While
providing excellent dimensional control, stopping
the sintering short of a full liquid phase
sintered state severely compromises the mechanical
properties otherwise attainable in a given
part. Due to the lower ultimate strength and
greatly reduced ductility, such a sintered
state is to be avoided. (close) |
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Is
it possible to enhance the mechanical properties
of sintered heavy alloy? |
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Yes. Post-sinter
processing is available to increase the ductility
and toughness of tungsten heavy alloys. This
should be strongly considered for mechanically
demanding applications where utmost "bend
before break" behavior is desirable. (close) |
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What
are "non-magnetic" tungsten heavy alloys?
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This term
erroneously implies that standard heavy alloys
exert some sort of significant magnetic field,
which they do not. Rather, this term denotes
alloys that, due to their chemical composition,
offer very low magnetic permeability. Such
alloys are commonly used for radiation shielding
in close proximity to electron optics or geomagnetic
devices.(close) |
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"Not
All Tungsten Heavy Alloys Are Created Equal"
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A radiation
equipment manufacturer was dealing with a
situation where a small radioisotope carrier
made of heavy alloy and fitted with a high
activity source posed a risk of source loss
from the main shielding container should the
single threaded stud be impacted during repositioning
of the shield. Concerned with the safety risk
posed by the scenario, the manufacturer was
told by the original supplier of heavy alloy
that potential fracture of the stud was unavoidable,
since "that's just how heavy alloy is". When
this equipment manufacturer later contacted
ATI Firth Sterling, property enhancement of
as-sintered heavy alloy was explained. After
subsequent adoption of this more ductile tungsten
heavy alloy, the impact scenario was experienced.
The threaded stud simply bent in response
to the blow, thereby preventing source loss
from the shielding and exposure of the attending
technician. This is but one illustration of
the advantages of using fully sintered heavy
alloy as produced by ATI Firth Sterling.(close) |
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"Stopping
the Leak" |
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A manufacturer
of downhole logging probes for the oil industry
was experiencing water leakage into instrument
housings made from tungsten heavy alloy during
high pressure qualification testing of the
probes. After technical discussions with ATI
Firth Sterling, it was apparent that the hydrostatic
leakage was not the result of lost structural
integrity but rather pressure assisted movement
of water through interconnected porosity in
the heavy alloy housing into the interior
electronics. It was explained that properly
sintered tungsten heavy alloys should be completely
hermetic in nature. When the manufacturer
switched to material produced by ATI Firth
Sterling, the problem vanished and acceptance
skyrocketed. Attention to metallurgical quality
counts!(close) |
