Aluminum base metals are classified in two
ways: as wrought alloys produced by mechanical working such
as rolling, extruding, or forging, or cast alloys produced
by pouring into a mold. Wrought alloys are further divided
as either heat treatable or non-heat treatable depending
on the composition.
Below is a basic step by step guide to follow
when welding aluminum.
Warning: Protect yourself & others. Read & understand this
Fumes & Gases can be hazardous to your health.
Arc Rays can injure eyes & burn skin.
Electric Shock can kill.
- Before use, read & understand the manufacturer's
instructions, Material Safety Data Sheets (MSDS) & your
employer's safety practices.
- Keep your head out of the fumes.
- Use enough ventilation; exhaust at the
arc, or both, to keep fumes & gases from your breathing
zone & the general area.
- Wear correct eye, ear, & body protection.
- Do not touch live electrical parts.
- See American National Standard Z49.1, Safety
in Welding, Cutting, & Allied Processes, published by
the American Welding Society, 550 N.W. LeJeune Road, Miami,
FL 33126; OSHA Safety & Health Standards, available from
the U.S. Government Printing Office, Washington, DC 20402
Select Joint Design & Fit up
Start by determining the best manner in which to join your
base metals. Correct joint design & fit up are critical
steps to insuring a strong bond upon weld completion. Be
sure to consider the degree of strength required, welding
position, metal thickness & joint accessibility.
The five basic types of joints are butt, corner,
edge, lap & tee. These five joints can be arranged in
many combinations to create a large variety of welds. Fixtures
& jigs are helpful in securing the work pieces in place
during the joining procedure. Sheet metal & most fillet
& lap joints should be clamped tightly over the entire length
of the work.
Choose The Welding Process
The most popular processes are Gas Metal Arc Welding (GMAW),
sometimes called MIG welding and Gas Tungsten Arc Welding
(GTAW) sometimes referred to as TIG welding. A third process,
Shielded Metal Arc Welding (SMAW) or stick welding, has
limited use on aluminum and is used primarily for small
repair jobs on material 1/8" or more thick.
- SMAW - Shielded
Metal Arc Welding or Stick Electrode
SMAW is an electric arc welding process
in which heat for welding is generated by an electric
arc between a covered metal electrode & the base metal.
The electrode coating provides shielding. The welding
equipment for this process is currently the most inexpensive
of the methods described here. However, electrodes do
create some inefficiency, such as stub loss & a slag
coating, which must be removed.
- GTAW - Gas Tungsten
Arc Welding - Tig Welding
Tig Welding is easily performed on a variety
of metals. It generally requires little or no post weld
finishing. It is an electric welding process in which
heat for welding is generated by an electric arc between
the end of a non-consumable tungsten electrode & the
base metal. Filler metal may be added, if necessary.
An inert shielding gas supplies shielding for the arc.
(Inert gas creates a protective atmosphere around the
welding in process).
- GMAW - Gas Metal
Arc Welding - Mig Welding
Gas metal arc welding is quick & easy
on thin-gauge metal as well as heavy plate. It generally
calls for little post weld cleanup. GMAW is an electric
arc welding process where heat is produced by an arc
between a continuously fed filler metal electrode &
the base metal. Shielding is obtained from an externally
supplied gas or gas mixture. The two most common types
of GMAW are:
Short Circuit Transfer - The
arc is broken or short circuited with each drop of metal
& restarted. Short circuiting transfer is not used
with aluminum welding.
Spray Transfer - Metal is transferred
across the arc creating a continuous spray of fine droplets
of metal. These droplets are projected down to the base
Determine The Appropriate Inert Shielding Gas
GTAW - Argon is suggested for thicknesses up to approximately
1/2". For thicker sections, argon-helium mixtures or pure
helium may be used. Pure helium may also be employed for
GMAW - Argon is used for most applications. It provides
deeper penetration and clean welds. Argon-helium mixtures
of 25 – 75% helium are helpful for thicker material (over
˝ inch). Helium produces a hotter arc which is sometimes
necessary due to aluminum’s high thermal conductivity. It
also produces a wider weld fusion shape.
Select The Applicable Filler Metal
Filler metal is based on several factors. One consideration
is the ability to provide suitable mechanical properties
for heat treatable and non-heat treatable base metals both
wrought and cast. Other important factors are freedom from
cracking, sevice conditions and weld color after anodizing.
#6. Set The
SMAW - uses a direct current (DC) or an alternating
DC uses either straight polarity, which
is electrode negative or reverse polarity, which is electrode
positive. Direct current flows in one direction continuously
through the welding circuit. There are several advantages
of DC. It works well at low current settings & with small
diameters. In addition, igniting the arc & maintaining a
short arc is easier.
AL-43 aluminum electrode is used with DC-reverse
AMPS - Recommended settings are:
x 14 "
GTAW - Manual GTAW of aluminum is usually
done using alternating current (AC). A high frequency generator
is employed for arc starting and stabilization. Pure or
zirconiated tungsten electrodes are used for AC welding.
Tungsten electrodes should be prepared with a hemispherical
The parameters for manual GTAW are dependent
upon plate thickness, weld position and joint design. The
following settings should be helpful in establishing a procedure.
Settings are for the flat position.
90 - 120
GMAW-Gas metal arc aluminum welding
is done using DC reverse polarity (electrode positive.)
Filler metal transfer is in the spray mode. Suggested settings
for flat position manual GMAW (argon shielding gas) are:
120 - 150
Clean The Base Metal
Cleaning should be done just prior to welding to prevent
the formation of oxides. The base metal surface must be
free of grease, oil, paint, dirt, etc. A clean surface will
provide a smoother, stronger joint. Brush the plate surface
& edges with a stainless steel wire brush to remove burrs
& oxides. Gloves should be worn to prevent hand oil or dirt
from getting on the joining surface.
Preheat If Applicable
Preheat is generally unnecessary in aluminum welding. In
some cases it can be helpful when welding casting to reduce
cracking tendency. It may also be useful to equalize weld
penetration when welding metals of different thicknesses.
A good welding technique is developed as a welder gains
experience. The following are basic welding tips:
- Use fixtures &/or jigs to help keep work
- Joints should be designed to provide suitable
access and to promote weld penetration
- Insure adequate shielding by centering
the filler metal in the gas & weld puddle area.
- For GMAW use a forehand welding technique
(gun pointed in the travel direction).
- In GTAW filler metal should be dipped into
the weld puddle, but should not drip into it.
- Move the torch/gun along the joint at a
steady, constant speed to maintain uniformity.
- Hold the torch/gun over the weld until
gas stops, to keep work protected.
Cooling/Post Weld Cleaning
Allow the joint to cool slowly. If AL-43 coated electrodes
are used, remove slag after welding.
Click here for a list of common welding problems and suggested
#12. Aufhauser Aluminum
Aufhauser manufactures a complete line of filler metals
for aluminum welding. Click on the following description
for information about sizes, composition, and part numbers: