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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. For more about
shot peening, select one of the following: Overview | Technical
Information | Photographs
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For
more information about Shot Peening, or other treatments offered
by Superior Shot Peening, click on one of the following:
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