|
NOISE
REDUCTION
| VIBRATION
& NOISE REDUCTION |
| TYPE
OF METAL |
RELATIVE
DECREASE IN AMPLITUDE VIBRATION /
CYCLE |
| Steel |
1.0
- 2.0 |
| As-Cast
Gray Iron |
20
- 60 |
| Heat-Treated
Gray Iron |
20
- 30 |
| As-Cast
Ductile Iron |
3.0
- 9.4 |
| Q
& T Ductile |
3.0
- 5 |
| Austempered
Ductile Iron |
10
- 15 |
Figure
3.1
|
All
gears make noise when they are operating.
Noise comes from the design, from allowable
variations in dimensional tolerances and from the
material used for the gear. With everything
else being equal, a set of gears made from a
material that has good damping characteristics
will be quieter than a set made from a material
that does not.
Graphite
flakes in gray cast iron will cause
significantly better damping properties by
comparison to any other ferrous
metal. The nodules in ductile iron
behave similar to the graphite flakes in
gray iron, cushioning vibrations as they
are transmitted through a part.
Figure
3.1 shows the relative damping capacity of
as-cast and heat treated gray and ductile
iron compared to steel.
The ability
to dampen vibrations using Dura-Bar means
that ductile iron gears will be quieter
than steel gears made to the same
dimensional tolerances and have similar
surface finishes. Gray iron gears
will be quieter than steel or ductile iron
gears and are an excellent choice for low
stress applications.
Figure
3.2 |
Automotive balance shaft gears require
high precision when made from steel in
order to meet the noise standard.
The tolerances are not as critical when
using gray or ductile iron, which allows
the gear to be made at a lower cost.
Figure 3.2
shows the qualitative relationship between
noise level and AGMA classification using
steel, ductile and gray iron.
HEAT-TREAT
DISTORTION
Iron
and steel grow when heat-treated because
of the volume change in the atomic
structure. With Dura-Bar, the growth
is predictable because of the strict
metallurgical process controls. Predictable growth minimizes additional
processing steps after heat-treat.
Plus...
-
Since
Dura-Bar does not require
carburizing, heat-treat distortion
caused by variations in the rate of
carbon diffusion into the part is
eliminated.
-
Due
to the continuous casting process,
Dura-Bar will not have residual
stresses that can be present in
rolled steel bars.
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