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Characteristics of Molybdenum
Molybdenum is a transition metal (refers to the "D" block of the
periodic table), or more strictly, "a transition metal as "an
element whose atom has an incomplete d sub-shell, or which can
give rise to cations with an incomplete d sub-shell". (source
Wikipedia). In its pure form, molybdenum metal is a soft,
silvery white metal which has one of the highest melting points
of all elements. The melting point of molybdenum is 2,623 °C
(4,753 °F), which is 2,000°F higher than the melting point of
steel. It is also 1,000°F higher than the melting point of most
rocks. Though it has the fifth highest melting point of all of
the elements, it has the lowest coefficient of thermal
expansion, making it a highly sought after component in high
temperature applications.
Though molybdenum has a very high melting point, it oxidizes
readily at temperatures in excess of 760°C. When exposed to air
at this temperature, an oxide layer sublimes as the base metal
reacts with oxygen, resulting in an oxidation process that
resembles smoke. When properly controlled, the oxide can be
recovered and reduced again to reclaim its molybdenum content.
To avoid oxidation loss however, molybdenum is often utilized in
inert or vacuum environments.
The largest use of molybdenum is as an alloy in the production
of steel and stainless steel where it improves the strength and
hardness of the alloyed metals. Ultra high strength steels with
up to 8% contained molybdenum can withstand pressures up to
300,000 pounds per square inch. It also improves the strength of
steel at elevated temperatures. In the United States, steel
production consumes approximately 60% of manufactured
molybdenum. In alloy applications, molybdenum content varies
from 0.5% to 8%, dependent upon desired characteristics.
Overall, iron and steel account for more that 78% of the worlds
molybdenum consumption.
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Typical
Chemical Analysis of Molybdenum Powder:
|
Element |
Wt% |
|
Al |
£0.002 |
|
C |
£0.007 |
|
Cr |
£0.0025 |
|
Cu |
£0.002 |
|
Fe |
£0.01 |
|
Ni |
£0.004 |
|
W |
£0.03 |
|
Co |
£0.002 |
|
Mg |
£0.001 |
|
Mn |
£0.001 |
| |
Medium |
Coarse |
|
O2 |
£0.15 |
£0.08 |
|
Mo |
99.95 Minimum excluding gases |
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Typical
Physical Properties of Molybdenum powder
| |
Medium* |
Coarse* |
|
Average Particle Size
by Fisher Sub-Sieve Sizer |
|
FSSS as Supplied |
2.0 – 3.5 |
3.5 – 6.0 |
|
Porosity as Supplied |
>0.60 |
>0.60 |
| |
|
|
|
Scott Density g/In3 |
12 – 25 |
15 – 30 |
|
Tap Density g/cc |
1.9 – 3.5 |
2.0 – 4.0 |
| |
|
|
|
Mesh Analysis |
>150 |
0–2% |
>150 |
0–2% |
|
<150 |
98% Min |
<150 |
98% Min |
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