Benefits of Shot Peening
Shot
peening is used in a wide variety of industries on
an even wider variety of parts. Parts typically shot
peened include: crankshafts, gears, torsion bars, springs,
valves, exhaust manifolds, blades, discs, turbines,
compressors, marine rudders, axles, hammers and anvils,
bicycle frames, landing gear, boat hulls, drill bits,
and pipeline. Depending on the specific part, shot
peening can accomplish all of the following:
- Increases fatigue strength
- Prevents cracking
due to wear, hydrogen embrittlement, corrosion and
stress
- Enhances lubricity by creating small pores
in which lubricants can accumulate
- Prevents fretting
- Prevents galling
- Creates a uniformly
textured, finished surface ready for immediate use
or for paint and coatings
- Can be used to curve
metal or straighten shafts without creating tensile
stress. This process is known as Peen forming.
- Can
permit the use of very hard steels by reducing brittleness
- Will
close up surface porosity in coatings
- Allows for
the substitution of lighter materials without sacrificing
strength and durability
- Can increases spring life
400% to 1200%
- Can increase gear life more than
500%
- Can increases drive pinion life up to 400%
- Can increases
crankshaft life 100% to 1000%
- Can increase the
fatigue strength of damaged parts extending the wear
and delaying replacement costs
If you have questions
about the benefits shot peening can bring to your
particular project, please contact
us. Our Phd.
Metallurgist and Mechanical
Engineer will be happy to assist you
in every phase of the project.
Other Shot Peening
Uses
Shot peening has become useful for a variety
of highly specialized applications. Our shot peening
technicians are skilled in all of the following alternate
specialized applications.
- Flow Treatment of
Pipe:
Used primarily in the transport of polymer pellets
used in the oil and gas industries. Polymer pellets
will slide against the inside of a smooth pipeline,
melt and form streamers or angel hair. These long
polymer fibers will contaminate the pellet flow and
clog up the transfer system. When the inside of pipeline
is roughened by shot peening, the polymer pellets
bounce or roll instead of sliding along the inside
of the pipe. The pellets' contact with the side of
the pipe is shortened, and formation of angel hair
is prevented.
- Peen Forming: Sheets of various metals
can be shot peened into concave, convex or flat shapes.
This shot peening application is especially prominent
in the aerospace and automobile industries. Shot
peening of automobile and aircraft has allowed the
industeries, over the years, to reduce the weight
of automobiles and airplanes by 30-50% saving (several
hundred pounds). This, combined with the fatigue-
and corrosion-resistance benefits of shot peening,
makes peen forming a highly useful technique.
- Straightening:
Shot peening can return bent shafts back into tolerance,
which will reduce waste or replacement costs
- Search
Peening: Corrosion is not always visible. Sub-surface
corrosion is particularly common in areas directly
surrounding metal fasteners, screws, nail, etc. Search
peening is a technique in which small, problem areas
are peened, and the hidden corrosion is exposed and
eliminated. Search peening is preferable to many
other corrosion removal methods because it actually
strengthens the metal while removing the corrosion.
History
of Shot Peening
Shot peening is not a new process.
People have long known that pre-stressing or work-hardening
metal could create harder and more durable metals.
The process of peening was used in forging processes
as early as the bronze age to strengthen armor, swords
and tools. Gun barrels in the civil war were subject
to peening to increase the hardness of Damascus steels,
and the fillets of crankshafts in early European
racecars were hand-peened with specially-made hammers
by 1922.
Of course, peening has evolved substantially
in the late 20th and early 21st centuries, but the
general idea remains
the same. Shot peening the material with thousands
of tiny balls of high-velocity shot works in much
the same way as peening with a hammer did in medieval
times.
So why does pre-stressing of metal work? The
atoms in the surface of a piece of manufactured metal
will be under (mostly) tensile stresses left over
from grinding, welds, heat treatments and other stressful
production processes. Cracks promulgate easily in
areas of tensile stress because the tensile stresses
are already working to pull the atoms of the metal
apart. By shot peening the material you introduce
a layer of compressive stress by compacting the material.
As
the shot peening is performed, the atoms on the surface
of the metal become crowded and try to restore the
metal's original shape by pushing outward. The atoms
deeper into the metal are pulled toward the surface
by their bonds with the atoms in the compressive layer.
These deeper atoms resist the outward pull creating
internal tensile stress that keeps the part in equilibrium
with the compressive stress on the surface. Tensile
stresses deeper in the part are not as problematic
as tensile stresses on the surface because cracks are
less likely to start on the interior.
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