Introduction to Welding Processes & Equipment
by Roger Garnett
Welding is a craft that can be performed reasonably by amateurs. As
always, good equipment is important for producing good work. The basics
and theory can be learned solo, and from books, but like many crafts,
learning from someone proficient is very desirable. A real good way to
start is to take some kind of night-school or similar beginning welding
class. You get exposed to various equipment and methods. There are often
advanced classes available, as well.
Among the first things a new welder needs to understand, is what the
different kinds of welding processes and equipment are, and their
application. A quick rundown:
Bonding by melting a soft metal to the surface of pieces to be
joined. Low temperature. Good for joining dis-similar materials.
Most common solders are lead-tin alloys.
A soldering process, where the surface of a metal is coated with solder.
A form of soldering, solder is used to fill in the surface of metal.
Similar to soldering, but uses a higher temperature to fuse the
filler metal to the work pieces. Stronger bond. (Includes "Silver
Soldering") Work heated to pre-melt temperatures.
Joining 2 similar work pieces by melting them together, usually
with an additional filler rod of some sort to take up space.
Materials must be similar.
Work is heated to melting point and beyond, and "cut" by
oxidizing metal. (Literally burning it away).
A barrier to keep oxygen away from heated work to prevent
oxidation. Includes chemical coatings called flux (liquids, pastes,
solids, which may be vaporized into a barrier gas when heated), and inert
gasses. Oxidation of the surfaces will prevent proper bonding of the metals.
Uses Flame from burning gas to create welding heat.
- Propane torch:
Good for sweating pipes, starting
fires, and spending hours trying to heat frozen bolts, while the
surrounding metal gets just as hot.
- oxyacetylene torch:
Cutting, welding, brazing, soldering, leading.
Most universal and useful welding tool. (Uses Acetylene gas and
Oxygen for hot flame.) With the right bits, rod, and technique, you can weld
almost anything. Good for cutting anything from sheet metal to the
turret off a tank, lead filling, brazing (a sort of hard soldering
process) welding plate, welding sheet metal, welding aluminium,
heating frozen bolts, or alternately cutting them off, drilling holes in
plate, welding cast iron, shrinking and forming steel, and can double as
a flame thrower in a pinch.
Drawbacks are: Overheating of some types of
work, harder to control quality of some processes.
Soldering, brazing, heating.
A cheap compromise between low cost and portable propane, and
Oxy-Acetylene. Better than the former, not as good as the latter.
Uses an electric arc to create welding heat.
- Basic AC & DC arc welders (AC is cheaper)
Uses flux coated steel (or other) rods of various types for different jobs.
Makes some of the best welds on heavy gauge
steels and cast iron. Cutting rods can make clean holes through thick
stock, and are about the only thing which can cut Kryptonite bike locks.
Very difficult to weld thin metals. You can also get a carbon arc torch
to use on an arc welder to braze. Eastwood's "stitch" welder is a gimmick
used on an arc welder to buzz the rod in and out, which may help on
thinner stock. (learning how to weld better, or going to a different
process is usually a better idea.)
- MIG (Metal Inert Gas):
A DC arc welding process which uses filler
metal fed in the form of a spool of thin wire, shielded by flow
of inert gas (CO2, Argon) instead of flux used in Arc. Very fast, much easier than Arc Welding,
with less heat buildup. Very good for sheet metal, due to minimal
heat distortion. Harder to weld thick stock, as welds are weaker
due to poorer penetration. The modern choice for steel body work, it
can also be used for Aluminium with Argon as the shield gas.
- TIG (Tungsten Inert Gas) :
A high frequency AC arc process which uses
a tungsten electrode shielded by an inert gas to create a fine,
controllable torch. Uses a separate filler rod, as in Oxy-Acetylene
welding. Capable of welding very thin metals. About the best
process for Aluminium, Stainless steel, and other exotic stuff.
- Resistance welding: includes spot welding:
Uses the heat generated
by electricity flowing through work to melt and fuse. i.e.- put an
electrode on either side of 2 overlapped sheets of steel, turn
on power. Metal in between heats up, and melts together.
An old favorite for assembling car bodies.
- Plasma Cutters:
Not a welder, but related. A high voltage arc is used to superheat
and ionize a stream of air to the "plasma" state. The stream of
plasma makes a rapid, clean, narrow cut with minimal heating of the
There is, of course, a wide range of equipment, capabilities,
quality, and pricing. The quality can make a big difference in
the ease of use and quality of work. "You get what you pay for."
Experience, and practice, practice, practice are very important.
Learning from an expert gets you there a lot faster.
© 1993, 1996 Roger Garnett