A clever Bronze-Age worker
was thinking outside the box one day 5,500 years ago when he came up
with an inspired idea. A great way of making things with the bronze
alloys that were being developed then, he reasoned, would be to heat
them until they started melting and pound them together with a hammer.
By combining heat and pressure in this way, craftsmen could make just
about anything that required a strong metal like bronze.
This was the birth of welding, a process that has had a major impact on metalworking and product engineering ever since.
Anything made of metal, no matter how big or small, can be
welded. Examples are everywhere, from vehicles like cars, trucks and
motorcycles to rail cars, ships, aircraft, rockets and space stations.
Construction is a huge market, and skyscrapers, bridges and highways
would be impossible to build without welding, as would oil and
natural-gas pipelines, offshore oil platforms, giant wind turbines and
solar panels. Welders help install and maintain boilers, antipollution
systems and other large structures, as well as piping for industrial,
commercial and residential facilities. Welding is even used by artists
to create sculptures and decorative items.
There is almost no limit to
what welding can do, especially since developments in the technology
continually improve its accuracy, quality and versatility. Welding
is, in fact, an increasingly high-tech skill. Welders are being trained
to operate robots and other automated systems that use powerful lasers,
electron beams and sometimes explosives to bond metals. The ability to work with computers and program software is consequently vital to the successful operation of these systems.
Don Howard, a welding specialist at Concurrent Technologies
Corp., an engineering firm in Johnstown, Pa., estimates that 20%-25% of
U.S. welding is automated and predicts this trend will grow by about 20%
in the next few years.
“A lot of very intelligent people are coming
into the welding community,” says Howard. There is money to be made, he
notes, but the industry also offers career paths. “Welding is not just
about working on a manufacturing line anymore. Once in the industry,
people know they can find a niche.”
“These are good times to be in welding,”
says Patricio Mendez, director of the Canadian Center for Welding and
Joining at the University of Edmonton in Alberta, Canada. Mendez notes
that students who like designing and building with metal and are
interested in fields such as materials engineering, robotics, lasers,
computer programming and systems integration will find plenty of career
opportunities in welding.
Many students are introduced to the process by virtual welding.
This simulation program is being developed by the Edison Welding
Institute (EWI) of Columbus, Ohio, to teach the basics of welding in
classrooms. “The objective is to give students a virtual experience that
is very much like the real thing,” says John Coffey, engineering
manager at EWI. The system uses sensors that duplicate the look and feel
of welding.
There are more than 80 welding processes. Most involve a
skilled worker using a high-heat torch (2,800-plus degrees Fahrenheit),
filler material that is usually in wire or stick form (though some welds
don’t use fillers) and pressure to permanently bond metal pieces.
Welding can also be used to cut and dismantle objects of all sizes as
well as for repairs.
The most common process is Gas Metal Arc Welding,
or GMAW. In GMAW, an electrode, which is also the filler, is
continuously fed through the nozzle of an arc torch. When the welder
activates the torch, several operations take place: The electrode begins
feeding through the nozzle, a direct current is generated that creates
an arc when it comes in contact with the electrode and shielding gases
are released around the nozzle to protect the weld from atmospheric
gases that could degrade its quality. The arc, whose movement the welder
controls, consumes the electrode, fills in the weld joint and creates
the weld.
Other widely used techniques like Gas Tungsten Arc Welding (GTAW) and Shielded Metal Arc Welding (SMAW)
are variations of the process. GTAW, for example, is a relatively
low-heat method that uses a non-consumable tungsten electrode. Its
low-heat characteristic reduces distortion in thin metals, such as those
used in aerospace. SMAW, also called “stick welding,” uses a
flux-coated consumable electrode ("flux" is a chemical cleaning agent
that removes oxidation from the metals to be joined) and is primarily
used for repair and steel welding. As the electrode burns, the flux
disintegrates, which releases a shielding gas that protects the weld
from degradation.
In more advanced welding technologies, lasers are combined
with GMAW in a hybrid process to make what one expert calls
“scalpel-like cuts” that are up to ½-inch deep, narrow and extremely
precise. The GMAW part of the process then deposits the filler and melts
it with a secondary heat source.
source:caeersinwelding.com
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