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- Information about technological processes
and working systems . Everybody can contribute with documentation,
that must be sended to info@rioweb.it
accompanied with the name of the source, and if possible the link
of the site one where there is the possibility of a deepening.
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Welding
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- A process used to join metals by the application
of heat. Fusion welding, which includes gas, arc, and resistance
welding, requires that the parent metals be melted. This distinguishes
fusion welding from brazing. In pressure welding joining is accomplished
by the use of heat and pressure without melting. The parts that
are being welded are pressed together and heated simultaneously,
so that recrystallization occurs across the interface. Joining
two or more pieces of material by applying heat or pressure, or
both, with or without filler metal, to produce a loxalized union
through fusion or recrystallization across the interface.
- Arc welding is the most common type
of welding. Standard arc welding involves two large metal alligator
clips that carry a strong electrical current. One clip is attached
to any part of the workpiece being welded. The second clip is
connected to a thin welding rod. When the rod touches the workpiece,
a powerful electrical circuit is created. The massive heat created
by the electrical current causes both the workpiece and the steel
core of the rod to melt together, cooling quickly to form a solid
bond. During welding, the flux that surrounds the rod’s core
vaporizes, forming an inert gas that serves to protect the weld
from atmospheric elements that might weaken it. Welding speed
is important. Variations in speed can change the amount of flux
applied, weakening the weld, or weakening the surrounding metal
by increasing heat exposure.
- Like arc welding, soldering and brazing
use molten metal to join two pieces of metal. However, the metal
added during the process has a melting point lower than that of
the workpiece, so only the added metal is melted, not the workpiece.
Soldering uses metals with a melting point below 800 degrees Fahrenheit;
brazing uses metals with a higher melting point. Because soldering
and brazing do not melt the workpiece, these processes normally
do not create the distortions or weaknesses in the workpiece that
can occur with welding. Soldering commonly is used to join electrical,
electronic, and other small metal parts. Brazing produces a stronger
joint than does soldering, and often is used to join metals other
than steel, such as brass. Brazing can also be used to apply coatings
to parts to reduce wear and protect against corrosion.
- The work of arc, plasma, and oxy-gas
cutters is closely related to that of welders. However, instead
of joining metals, cutters use the heat from an electric arc,
a stream of ionized gas (plasma), or burning gases to cut and
trim metal objects to specific dimensions. Cutters also dismantle
large objects, such as ships, railroad cars, automobiles, buildings,
or aircraft. Some operate and monitor cutting machines similar
to those used by welding machine operators. Plasma cutting has
been increasing in popularity because, unlike other methods, it
can cut a wide variety of metals, including stainless steel, aluminum,
and titanium.
More information:
- http://www.bls.gov/oco/ocos226.htm
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