Tig Welding Aluminum Part 2
THE RELEVANCE TO WELD PROCESS CONTROL: In
the nineteen nineties, Ed set the first multi-robot robot line in North America,
to weld a large aluminum application as seen with ABB robots welding aluminum
golf cart frames, (above photo). Ten years later, in contrast to more than 80%
of the robots in the auto industry welding "carbon steel" parts, the
four robots welding aluminum frames achieved much greater robot production efficiency,
less down time and less weld rework.
In 2008, the robots and the MIG weld
equipment have far surpassed the welding needs of today's applications, with this
in mind, one can only wonder how much robot MIG weld quality and productivity
improvement could be made in the auto / truck industry, if management focussed
on process welding expertise as provided
in Ed's robot weld process control training resources.
set the robot welds on this golf cart frame and also trained
the ship yard
welders on flux cored welding for this ship in Philadelphia.
A GREAT CONCERN WITH ROBOTS AND ALUMINUM WELDS WAS WIRE FEED ISSUES AND WIRE BURN
BACKS TO THE CONTACT TIPS: TO GET THEIR ROBOT CONTRACT, CLUB CAR REQUIRED THAT
ROBOT COMPANIES PERFORM A WELD TEST THAT REQUIRED A ROBOT PROVIDE 10,000 ROBOT
ARC STARTS ON ALUMINUM SHEET METAL, RESULTING IN NO MORE THAN 10 WIRE BURN BACKS
OR 10 WIRE FEED ISSUES WITH 0.046 ALUM WIRE.
NOTE, THIS TEST HAD TO BE DONE "WITHOUT
THE USE OF PUSH PULL GUNS".
THE BEST PULSED POWER SOURCE (OTC) AVAILABLE) IN THE 1990s AND STILL ONE OF THE
BEST PULSED UNITS AVAILABLE IN 2008, ED COMPLETED THE ROBOT MIG ALUMINUM WELD
TEST. HE ACTUALLY GOT TO 7000 ARC STARTS WITHOUT A SINGLE WIRE BURN BACK. ED WAS
WORKING WITH THE HIGHLY QUALIFIED ABB ROBOT PERSONNEL IN FORT COLLINS CO. USING
ABB ROBOTS, A TRADITIONAL MIG GUN (NO PUSH PULL), AN OTC POWER SOURCE, AN ALCO
TECH WIRE DEREELER, HARD PLASTIC LINERS AND OF COURSE AT THAT TIME HE APPLIED
35 YEARS OF MIG WELD PROCESS WELDING EXPERTISE
TO THE ROBOT PROGRAM.
was the senior weld engineer for ABB Robotics Div. Fort Collins. CO).
production efficiency can be greatly influenced
when you have robots working
Problem with multi-robot weld cells. When
one robot has a weld
issue that has to be rectified, the other 3 will not
The robot application had four ABB robots in a
single cell working together on a complex aluminum golf cart frame.
No push-pull guns were utilized and the wire feed distance from the feeders to the guns was typically 20 to 30 feet. The customer was concerned that with the typical
aluminum wire feed and arc start issues with aluminum that four robots working
together involved some risk. To attain confidence in the project the customer
requested a test phase with a robot producing ten thousand arc starts with no
more than ten arc ignition issues.
I set the initial aluminum test data to ensure
no weld start issues and after 7000 arc starts without a single burn back or arc
ignition issue, the customer was satisfied that ABB should get the contract. I then established the robots welds
to compensate for the aluminum gage part fit and gap issues and of course provided
optimum start and stop data. Each of the
ABB robots produced approx. 30 to 40 welds per-frame.
 ABB provided
an automatic torch alignment system. The ABB system can make 3-D and angular calculation
via its BullsEye automatic TCP calibration system.
The ABB Bulls Eye system automatically adjusts the TCP program to the torch, eliminating
the need for touchups and minimizing down time
 The ABB system also
provided automatic error-handling capability-a necessary feature when robots are
in close proximity the robots complete almost 130 welds on each frame.
ABB used robot I/O between all four robots. If one robot had an error, it communicated
the error the other three. The other robots would then finish the weld they are
doing, but will not move to the next
weld until they receive a "clear to go" signal. In the meantime, the
robot with the error automatically goes to a service position where an operator
checks the problem.
four robots to weld simultaneously on a small frame application was a challenge
easily handled by ABB. Adding to the complexity was the need to program error
handling as well as welding. Each group of welds had to have its own error handler
program, so developers had to keep in mind the path of each robot and make sure
that it wouldn't cross the path of another robot.
 The robots used regular
MIG guns, push pull guns were not necessary.
 For optimum wire feed,
we set Alco Tech dee-reelers and hard plastic liners.
aluminum robot production began in early 1998. Since that time, the company has
produced more than 100,000 aluminum golf cart frames. Two people operate the system,
one loads a fixture in one cell, while the robots are welding in the other cell.
Arc on time for the 130 welds on the cart frames was approx. 6 minutes as compared
with 27 minutes for the welders to manually weld the frames.
11 year old project, is in 2008 welding aluminum frames with multi-robots in close
proximity and attaining far superior robot weld quality and production efficiency
than the majority of robot "carbon steel" frame weld applications as
found in global auto / truck plants.
IRRESPECTIVE OF THE "NEW" WELD APPLICATION YOU
ARE WORKING ON TODAY. IT'S LIKELY SOMEONE IN THE PAST HAS PRODUCED THE WELDING
RESULTS YOU ARE SEARCHING FOR.
IN MIND THAT WELD SKILLS HAVE MINIMAL IMPACT ON ROBOT WELD QUALITY AND PRODUCTIVITY.
IN CONTRAST, WELD PROCESS KNOWLEDGE AND WELD EQUIPMENT / CONSUMABLE KNOWLEDGE
WILL OVERCOME THE GREATEST ROBOT / AUTOMATED WELD CHALLENGES. Ed Craig 1989
/ ABB Arcitec / Aluminum Weld Issues.
Welds on Ford
6061 Aluminum Car Seats.
2000, I was requested by an engineer at VAW a tier one supplier to analyze the
welding performance of their ABB robot and ESAB Arcitec welding equipment. This
plant produces extruded aluminum parts. The aluminum welded car seats were for
Ford. The car seats and parts required small welds which were made on thin gage
the installation of the robot cells, continuous production of optimum weld quality
parts has been impossible due to the issues documented in this report. Weld
reject rates averaged sixty percent and the robot down time per hour averaged
20 to 30 minutes. This was one of those situations in which the ESAB welding power source selected was simply not capable for the application. For the rest of the Aluminum story click here.
are more than 400 wrought aluminum alloys,
and over 200 aluminum alloys in
the forms of
and ingots registered with
the Aluminum Association.
Aluminum Alloy Designations have 4 digits.
Alloying Elements. Aluminum
is alloyed with a number elements to provide improved weldability, strength and
corrosion resistance. The
primary elements that alloy with aluminum are;
digit is principle aluminum alloy. First digit also describes the aluminum series.
Ksi is ultimate tensile strength range.
> 99% Aluminum
non heat treatable
Alu - Copper
2 - 10% provides strength and allows precipitation hardening. Watch
for weld solidification cracking
Provides increased strength
non heat treatable
melting temperature, welds more fluid. When combined with magnesium provides an
alloy that can be heat treated.
heat treatable and none heat treatable
Alu - Magnesium.
none heat treatable
Creates a unique
compound magnesium silicide Mg2Si. Allows special heat treat properties, suitable
for extrusion components
18 - 58 ksi
When you add zinc copper and
magnesium you get a heat treatable alum alloy of very high strength. Watch for
stress corrosion cracking. Some alloys MIG weldable some not
32 -88 ksi
Heat Treatable Aluminum Alloys. With
these alloys it's possible to increase the alum strength through cold working
or strain hardening. To attain the desired strength, a mechanical deformation
must first occur in the aluminum structure, the deformation will result in increased
resistance to strain producing both higher strength and lower ductility.
These alloys are different from "heat-treatable alloys" as the non-heat
treatable alloys cannot form second-phase precipitates for improved strength.
Non-heat-treatable alloys cannot achieve the high strengths characteristics of
heat treatable precipitation-hardened alloys.
The absence of precipitate-forming
elements in the low- to moderate-strength, non-heat-treatable alloys is beneficial
from a welding perspective as many of the alloy additions needed for HEAT TREATABLE
precipitation hardening, copper plus magnesium, or magnesium plus silicon can
lead to hot cracking during welding. The heat affected zone (HAZ) mechanical properties
are higher in not-heat treatable alloys as the HAZ is not compromised by coarsening
or dissolution of precipitates.
wrought aluminum alloys can be placed into one of four groups,
Al (Al 99% minimum purity)
3xxx Al + Mn
4xxx Al + Si (some exceptions)
Al + Mg
and MIG Filler
alloys used to join non-heat-treatable alloys typically come from three alloy
used TIG and MIG filler alloys for none heat treatable alloys include,
5554, 5654, 5183, 5356, 5556.
MIG or TIG welding "non-heat treatable" aluminum alloys, note that the
HAZ will be annealed during the weld. The none heat treatable alloys are annealed
during welding in the 600-700 F, range, the time required at this temperature
is short. The alum welds will have minimal impact on the transverse ultimate tensile
strength of a groove weld as the annealed HAZ of the none heat treatable alum
alloys will usually be the weakest area of the weld joint.
qualification for the none heat treat alloys is typically based on the minimum
tensile strength of the alum base alloy in its annealed condition.
welding the non-heat-treatable alloys microstructure damage will occur in the
HAZ. The HAZ damage in non-heat-treatable alloys is however minimal effecting
both recrystallization / grain growth. In contrast with the heat treatable alloys
the mechanical properties loss is extensive.
welding all aluminum alloys, please note: To help retain the properties
in the Aluminum HAZ locations, always use low to conservative TIG or MIG weld
parameters, think low weld heat. Low weld heat is one of the great real world
benefits of using the pulsed MIG weld transfer mode on aluminum applications.
For the none heat treatable series that require strength, the
5xxx- alloys are popular for applications where good joint strengths can be obtained
in the as-welded condition without the need for post-weld heat treatment.
The 1xxx, 3xxx, and 5xxx series wrought aluminum alloys are non-heat
treatable and are strain hardenable only.
treatable aluminum alloys attain
their optimum mechanical properties through thermal controlled heat treatment.
2xxx, 6xxx, and 7xxx series wrought aluminum alloys are heat treatable. In contrast
4xxx series consist of both heat treatable and non-heat treatable alloys,
beware of hot
cracking with some of these alloys.
treatable alloys attain their mechanical properties through thermal treatment.
Solution heat treatment and artificial aging are the most common methods.
Solution Heat Treatment is
the process of heating to temperatures (around 990 Deg. F). In this temperature
range the alloying elements or compounds go into solution. After heating the part
is quenched typically in in water. The quench produces a supersaturated solution
at room temperature. Solution heat treatment is usually followed by aging.
Aging. The precipitation
of a portion of the elements or compounds from a supersaturated solution in order
to yield the required properties.
treatable aluminum alloys after welding. These
alloys through "post heat treatment" after welding can regain the strength
lost during the welding process. When post heat-treat is applied to these alloys
the heat must place the alloy elements into solid solution. The second step is
provide controlled cooling after the heat treatment, this produces a supersaturated
solution. The third and final step in the heat treat process is to maintain the
welded part at a low temperature. The time has to be long enough to allow a controlled
amount of precipitation of the aluminum alloying elements.
affect of a weld on a heat treated alum alloy HAZ is partially annealed and overaged,
remember the higher the weld joules (volts - amps- travel speed) with heat treatable
alloys, the lower the as welded strength of HAZ locations.
heat treatable or none heat treatable aluminum alloys, the differences between
the MIG and TIG heat affected weld zones (HAZ) and the base metal affected by
the weld heat can be significant.
With none heat treatable aluminum alloys
in the 1xxx - 3xxx - 4xxx - 5xxx series, the reduction of the HAZ tensile strength
is typically predictable under normal weld conditions. In contrast the HAZ area
strength with heat treatable alloys 2xxx - 6xxx - 7xxx can be reduced below the
minimum tensile strength required for the parts when the welding heat is excessive
during the weld. Higher tensile strength from the filler and reduced strength
from the part influenced by the annealing effect of the weld and you have hot
cracking in the HAZ of the base metal.
Designations. Aluminum alloys can be classified by a temper designation.
O = Annealed,
T = Thermally
F = As fabricated,
H = Strain hardened;
W = Solution heat-treated
which can designated both heat treatment, or cold working aging.
aluminum alloys are alloys that are rolled from ingot or extruded. Alloys
can also be divided into a cast group of alloys. Cast alloys are those used to
manufacture parts from molten alloys of aluminum poured into molds. Cast alloys
are precipitation hardenable but never strain hardenable. The weldability of cast
alloys is affected by casting type - permanent mold, die cast, and sand. A three-digit
number, plus one decimal i.e. 2xxx designates the copper cast alloys.
Aluminum Alloy Designations:
Casts have three digits and one decimal place (XXX.X).
XXX .X (.X - .O = casting - .1
or .2 = ingot)
If a capital letter precedes the numbers this is a modified
digit of cast aluminum alloys is the principle alloy. First digit also describes
the aluminum series.
+ Cu and or magnesium|
Weldable grades of aluminum castings are
319.0, 355.0, 356.0, 443.0, 444.0,
520.0, 535.0, 710.0 and 712.0.
Physical Properties. Lets
look at how aluminum compares to steels.
The typical weld characteristics of steel or stainless don't apply when mig or
tig welding aluminum. Aluminum has higher thermal conductivity and lower melting
temperatures, both factors will influence weld solidification, weld burn through
potential and warpage problems.
Aluminum is three times lighter than steel and yet can offer high strength when
alloyed with the right elements.
 Aluminum can conduct electricity
six times better than steel and nearly 30 times better than stainless steel.
 Aluminum provides excellent corrosion resistance.
 Aluminum is easy
to cut and form.
 Aluminum is nontoxic for food applications.
 Aluminum is nonmagnetic therefore arc blow is not a problem during welding.
 Aluminum has a thermal conductivity rate five times higher than steel.
The high thermal conductivity creates a great heat sink which can create insufficient
weld fusion on parts over 4 mm and weld burn through issues on parts less than
3 mm. The weld fusion concerns is one reason to consider spray transfer instead
of pulsed on specific alum applications.
 Aluminum provides welds that
are less less viscous which is a problem when trying to get weld fusion with the
short circuit mode. Pulsed MIG is beneficial on all thin aluminum applications.
The viscosity is beneficial when using spray or pulsed transfer for all position
 Aluminum has a low melting point 1,200 degrees F, this is more
than half that of steel. For a given MIG wire diameter the transition short to
spray weld current for aluminum is much lower than it is for steel.
Minimum 99% aluminum. This
very low strength series is considered none-heat treatable and is used primarily
for bus bars and some pipe and chemical tanks. This alloy provides superior corrosion
resistance. Alloys with purity levels greater than 99,5% are used for electrical
conductors (for example alloy 1350). 1XXX series are easily welded with 1100 and
Alu-Copper provide approx.
2 to 6% Cu with small amounts of other elements. The Cu increases strength and
enables precipitation hardening. The 2XXX series is mainly used in the aerospace
industry. Most of the 2XXX alloys have poor weldability due to their sensitivity
to hot cracking. These alloys are generally welded with 4043 or 4145 series filler
electrodes. These filler metals have low melting points which help reduce the
probability of hot cracking. Exceptions to this are alloys 2014, 2219 and 2519,
which are readily welded with 2319 filler wires. Hot cracking sensitivity in these
Al-Cu alloys increases as copper is added up
to 3% and decreases when the copper is above 4.5% Be wary of Alloy 2024 as it
is crack sensitive.
Alu-Manganese when added
to aluminum produces a moderate strength, none-heat treatable series typically
used for radiators, cooking pans, air conditioning components and beverage containers
and storage equipment. The 3XXX series is improved through strain hardening which
provides improved corrosion properties and improved ductility. Typically welded
with 4043 or 5356 electrode, the 3XXX series is excellent for welding and not
prone to hot cracking. The moderate strength of this series prevent these alloys
from being utilized in specific fabrication or structural applications.
Alu-Silicon reduces melting
temperature improves fluidity. The most common use is as a welding filler material.
The 4xxx-series alloys have limited industrial application in wrought form. If
magnesium added it produces a precipitation hardening, heat treatable alloy. The
4XXX series has good weldability and can be a non-heat-treatable and heat treatable
alloy. Used for castings, weld wires. The 4xxx wires are more difficult to feed
than the 5xxx series.
Alu-Magnesium increases mechanical properties through solid solution strengthening
and improves strain hardening potential. These alloys have excellent weldability
with a minimal loss of strength. The 5 XXX series has lower tendency for hot cracking.
The 5XXX series provide the highest strength of the nonheat-treatable aluminum
alloys. These alloys are used for cryo vessels, chemical storage tanks, auto parts,
pressure vessels at elevated temperatures, cryogenic vessels as well as structural
applications, railway cars, trailers, dump trucks and bridges because of the corrosion
resistance. 5xxx looses ductility when welded with 4xxx series fillers due to
formation of Mg2Si.
Series and Weld Crack Sensitivity: The
5xxx typically while welding with or without filler metal have low crack sensitivity.
Usually the filler metal will have a little more Mg than the base metals being
welded. Be wary of 5052 especially if TIG welding without a filler metal, use
a high Mg filler like 5356 for the 5052 alloy. All aluminum concave fillet welds
and concave craters are sensitive to hot cracks.
Alu-Magnesium & Silicon
(magnesium-silicides) combine to serve as alloying elements for this medium-strength,
heat-treatable series. 6XXX are principally used in automotive, pipe, structural,
railings and extruded parts. This series can be prone to hot cracking, but this
problem can be overcome by the correct choice of joint and filler metal and weld
procedures that minimize weld heat input. This series can be welded with either
5XXX or 4XXX series, adequate dilution of the base alloys with selected filler
alloy is essential. 4043 electrode is the most common filler metal for this series.
Be wary of liquation cracking in the HAZ when using specific 5xxx alloys. See
Liquation cracking above notes.
Crack Sensitivity: As many
of the 6xxx alloys have 1.0% magnesium silicide, these alloys are crack sensitive.
Avoid welding without filler metal and do not use a 6xxx material as a filler
metal. Using 4xxx or 5xxx filler metals reduces crack sensitivity as long as sufficient
weld metal is added and good weld dilution occurs with the 6xxx base metals. Avoid
weld joints in which minimal weld dilution occurs, a vee prep is superior to a
square groove. All 6xxx aluminum applications that have concave welds and concave
craters are sensitive to hot cracks.
Alu-Zinc when added to aluminum
with magnesium and copper permits precipitation hardening and produces the highest
strength heat-treatable aluminum alloy. These alloys are primarily used in the
aircraft industry, armored vehicles and bike frames. The weldability of the 7XXX
series is compromised in higher copper grades, as many of these grades are crack
sensitive (due to wide melting ranges and low solidus melting temperatures.) And
susceptible to stress corrosion cracking. Grades 7005 and 7039 are weldable with
Crack Sensitivity: The 7xxx
Al-Zn-Mg alloys (typically welded with 5356 avoid 4043) resist hot cracking better
than the 7xxx Al-Zn-Mg-Cu alloys.
Other elements that are alloyed
with aluminum (i.e. lithium) all fall under this series. Most of these alloys
are not commonly welded, though they offer very good rigidity and are principally
used in the aerospace industry. Filler metal selection for these heat-treatable
alloys include the 4XXX series.
weld equipment issues
and lack of aluminum welding process expertise:
company I visited welds 6xxx series, extruded aluminum, thin gage parts. They
had purchased a Panasonic VR OOGAL 11robot, with a Panasonic 350 amp Panastar
RA 350 pulsed power source. For the welds they used an 0.046, 4043 wire and
argon. The MIG wire spool was mounted on top of the robot, and they used a regular
four-drive roll feeder with a water-cooled gun. The
problem robot welds were short lengths, 5/8 to ¾ long. The robot welds
are made on aluminum square tubes 0.070 thick. The 6xxx tubes are welded to a
thicker alum part 3/16 thick. Since they purchased the robot the completed welds
never look consistent over their short lengths. All the thin tube welds were made
with the same weld data, yet in the same locations on the parts, some welds look
fluid while other welds look cold. Most of the welds ended up with a black and
dirty appearance yet the push gun angle is correct. These welds caused so many
issues the company was ready to give up the robot and go back to manual TIG. For
the rest of the story, click here.
A Combination of Balance
Wave Control Power Source and
is the ultimate tool to attain
optimum aluminum welds with minimum
Welding Tips and Information
alloys provide unique physical properties.
Weight. Aluminum is three
times lighter than steel and yet aluminum can provide higher strength when alloyed
with specific elements.
None Magnetic. Since
aluminum is nonmagnetic, arc blow is not a problem during aluminum welding.
Thermal Conductivity. With a thermal conductivity rate that is five to six
times higher than steel and the aluminum welds watch out for lack of weld fusion
especially at the weld starts. With alum being more sluggish and less fluid, aluminum
can be welded in all positions with spray and pulsed with relative ease. In contrast
to steel the high conductivity of aluminum acts as a heat sink making weld fusion
and weld penetration more difficult to achieve on parts > 4 mm.. However on
thin parts, the rapid build up of heat in the alum parts can add to high weld
fluidity and weld burn through potential.
Porosity and Hydrogen. When
MIG or TIG welding aluminum, the weld decision maker should always be aware that
this is one of the metals most susceptible to porosity.Hydrogen
dissolved in the liquid weld metal will try to escape as the aluminum solidifies
and the trapped hydrogen will result in weld porosity which is often extensive.
The main cause of porosity in aluminum welds
is the absorption of hydrogen in the weld pool which forms gas pores in the solidifying
weld metal. The most common sources of hydrogen are hydrocarbons and moisture
from contaminants on the aluminum base metal and on the filler wire surface. Also
water vapor from the MIG or TIG shielding gas will provide the same results.
cracking is common with carbon steels but hydrogen cracking will not occur with
aluminum. Hot cracking or solidification cracking is a primary cause for aluminum
Welds and Solidification Cracking.
Solidification cracks can happen due to thermal expansion and contraction during
the aluminum these factors generates high stresses sometimes tearing the weld
causes of alum solidification cracks.
incorrect choice of alum weld consumable.
[b] Concave welds, undersize
welds, and welds with insufficient weld throat. (The weld throat depth must be
sufficient to compensate for the weld contraction stresses).
[c] Weld joints
[d] Poor weld weld geometry.
[e] Poor weld joint design.
Weld restraint and weld stresses can be reduced by focussing on the weld edge
prep, the weld sequence.
[f] Excess weld heat, watch weld pass sequence
and on multi-pass welds consider interpass temperature control.
cracking is reduced with the selection of crack-resistant filler metal like the
4xxx and 5xxx filler metal. Be wary when choosing the filler metal to specifically
reduce weld cracking, as the weld metal may provide lower strength than the parent
metal and will not respond to heat treatment if applied.
Liquation Cracking. In contrast to hot cracking
which occurs in the weld, while MIG or TIG welding aluminum liquation cracking
will occur in the heat affected zone (HAZ). With liquation cracking low melting
point films are formed at the grain boundaries and these films (liquid elements)cannot
withstand the contraction stresses during the weld metal solidification. Heat
treatable alloys, like the 6xxx and 7xxx series are sensitive to liquation cracking.
To reduce the potential for liquation cracking, consider a weld wire with a lower
melt temperature than the parent metal. With alloy 6061 - 6082, liquation cracking
can occur in the partially melted zone when a weld with good dilution is made
with 5356 or similar filler metal is utilized. In contrast when welding the same
alloys with 4043 liquation cracking should not occur.
it takes is a little TIG - MIG weld process knowledge
to not produce welds
will combine with oxygen to form an aluminum oxide layer. This layer will form
instantly as the aluminum surface is ground or machined. The aluminum oxide layer
while very thin can also be very porous. The oxide layer will readily trap moisture,
oil, grease and other materials adding to the potential for hydrogen pickup. The
aluminum oxide layer provides excellent corrosion resistance, however this layer
must be removed before welding as it prevents fusion due to its higher melting
point (3700 degrees F). The weld arc gas molecules, the fore hand (push) technique,
mechanical cleaning, wire brushing, solvents and chemical etching and voltage
control are used for the oxide removal. One of the best practices to attain clean
alum MIG welds is to use the lowest possible voltage which assures a short arc
length, and a concentrated plasma which is beneficial for the oxide removal.
alloys that are difficult to weld.
that may be sensitive to hot cracking are found in the 2xxxseries, alum-copper and in the 7xxx series
With the 2xxx series hot cracking sensitivity increases with
Cu < 3% and decreases with Cu > 4.5%. Avoid weld practices that promote
high heat input as grain boundary segregation cracking potential.
alloys that contain Al-Zn-Mg like 7005 resist hot
cracking and have better mechanical weld properties than Al-Zn-Mg-Cu alloys like
7075 that contain small amounts of Mg and Cu
which extend the coherance range
increasing the crack sensitivity. Zirconium is added to refine grain size and
reduce crack potential. Electrode 5356 is often recommended for this group as
the magnesium helps prevent cracking. The 4043 electrode would provide excess
Si promoting brittle Mg2Si particles in the welds.
Be careful when welding
dissimilar alum alloys as extending the coherence range increases the crack sensitivity.
When welding alloys that do have good weldability like welding a 5xxx alloy to
a 2xxx base alloy or a 2xxx filler on a 5xxx alloy and vice a versa you can end
up with high Mg and Cu and increase the coherence range increasing the crack sensitivity.
Common Aluminum MIG Filler Welding Metals:
5356 - 4043 - 1100 - 5556 -
the filler metal selected should be similar in composition to the base metal alloy
for example a 1XXX filler wire for welding 1XXX - 3XXX-series base metal alloys.
Special consideration is however required when weldability is an issue. Weldability
of non-heat-treatable aluminum alloys should be measured in resistance to hot
cracking and porosity potential. Hot cracking issues are encountered when welding
with alloys sensitive to cracking, alloys subject to excess heat or parts that
are highly constrained.
Cracking issues can occur when low strength
weld alloys like 1XXX are used to join 5XXX alloys (or vice versa) or when welding
dissimilar metals with different strengths. The best filler metals when hot cracking
occurs is to use 4xxx fillers.
considering an aluminum MIG filler metal make sure you ask the right filler metal
the best alum filler for "corrosion resistance"?
best alum filler to "match the color" of the base metal?
the best alum filler for carrying "high weld current"?
the best alum filler for "good weld crack resistance"?
the best alum filler for the "desired strength"?
the best alum filler for "high temp or low temp service"?
mechanical properties such as yield, tensile strength and elongation are affected
by the choice of aluminum base and filler alloys.
groove welds, the heat affected zone (HAZ) dictates the strength of the joint.
The non-heat-treatable aluminum alloys HAZ will be annealed and their HAZ will
be the weakest point.
Heat-treatable alloys require much longer periods
at annealing temperatures combined with slow cooling to completely anneal them
so that weld strength is less affected. When welding alum please remember that
preheating, excess interpass temperatures and and excess weld heat from over sized
welds, slow weld speeds and weaving all increase temperature and time at temperature
all can influence the strength levels that will be attained.
contrast to groove welds the fillet weld strength is dependent on the composition
of the filler alloy used to weld the joint. For example the selection of 5XXX
instead of 4XXX can provide twice the weld strength.
to use either
4043 or 5356 filler wire?
aluminum filler wire is an aluminum wire with
5% silicon. This wire was developed for welding the 6xxx series aluminum alloys.
4043 may also be used to weld the 3xxx series or 2xxx alloys. 4043 is also used
for welding castings.
 4043 has a lower melting point and provides
more weld fluidity than 5xxx series filler alloys. 4043 will provide cleaner "less
black soot because it doesn't contain magnesium.
 4043 is often preferred
by welders as it provides better weld wetting, smoother weld surface more stable
transfer and is also less sensitive to weld cracking when welding the 6xxx series
 4043 provides more weld penetration than 5356, however
the 4043 will produce welds with less shear strength and ductility than those
made using 5356.
4043 is used for applications when the service temp above 150 F, in contrast 5356
is not suited to applications where prolonged heat is applied.
4043 is not well suited for welding Al-Mg 5xxx alloys and should not be used with
5xxx alloys with > 2.5% Mg, alloys such as 5083, 5086 or 5456 as excess magnesium-silicide
(Mg2Si) can develop in the weld structure decreasing ductility and increasing
crack sensitivity. (One exception to this 4043 rule is when welding the 5052 alloy
which has a low magnesium content.)
When shear strength is the concern consider 5xxx rather than 4xxx filler metals.
As welded 4043 will provide lower ductility than 5356, this is important if you
are shaping the welded part after welding to remember this fact.
For MIG wire feedability note the 4043 or 1100 are softer than 5356 so expect
more wire feed issues.
wire is an aluminum wire
with 5% magnesium. This is the most common aluminum filler wire due to superior
strength, ductility and superior MIG wire feedability. 5356 was developed to weld
the 5xxx structural alloys and also the 6xxx series extrusions. Do not use the
5356 on castings as they are high in silicon. 5356 is not suited to weld applications
in which the service temperatures exceed 150 degrees Fahrenheit (65 degrees Celsius).
The formation of Al2Mg at elevated temperatures at the grain boundaries makes
the alloys prone to stress corrosion. For components that will be anodized after
welding, 5356 is recommended for the best color match, in contrast 4043, will
turn black when anodized.
Strength and Weld Heat Considerations:
mentioned, typically the resulting HAZ of a groove weld will determine the strength
of the joint and usually a variety of filler alloys will match or exceed this
strength requirement. However, there are many other factors for consideration
when welding the heat treat or non-heat treatable alloys.
treatable alloys require a specific time at temperature to fully reduce their
strength. The strength reduction in the heat treatable alloy may be minimal or
extensive during the welds, defendant on the weld procedures and technique and
fixtures utilized. The amount of strength loss due to weld heat is influenced
by both time / temperature. Faster weld speed or smaller welds produce less weld
heat in the weld area. Fixtures that provide heat sinks lower the weld heat input.
The lower the weld heat the higher the as welded strength.
can add unnecessary weld heat and require consideration on the influence of weld
heat on aluminum alloys;
 lack of interpass weld temperature controls
on, multi-pass welds.
 excess preheating,
 slow weld speeds,
 wide (8 mm) weld weaves,
 oversized welds,(>6 mm fillets),
 welding thin parts or many welds concentrated is a small area,
high weld current and voltage.
or Tensile Strength. In contrast to aluminum groove welds, the fillet weld
strength is mostly dependent on the composition of the alum filler alloy used.
The fillet joint strength is based on shear strength which can be affected considerably
by filler alloy selection.
When welding alum structural applications
and considering the 5xxx series or 4xxx series filler metals, the tensile strength
of groove welds differences may be minimal. However serious consideration is required
when considering the shear strength of aluminum "fillet welds". The
approx. transverse shear strength of 4043 is around 15 ksi while the shear strength
of 5356 is approx. 26 ksi. The bottom line the 5356 provides superior ductility
and shear strength.
TYPE AND FILLET WELD SIZE: Alcotec reports that tests have shown that a required
shear strength value in a fillet weld in 6061 base alloy required a 1/4 inch (6
mm) fillet weld with 5556 filler compared to a 7/16. (11 mm) fillet with 4043
filler alloy to meet the same required shear strength. This can mean the difference
between a one run fillet and a three run fillet to achieve the same strength.
and alum welds may be a consideration if forming is to be performed after welding
or if the alum weld is going to be subjected to impact loading. Also ductility
should be given consideration when bend tests are applied during weld procedure
In contrast to the 5xxx series, the 4xxx series
filler alloys provide lower weld ductility, this is addressed with special requirements
within the code or standards relating to the weld test sample thickness, bending
radius, and material condition.
Resistance: Most aluminum base alloy filler alloy combinations provide satisfactory
protection for against general exposure to the atmosphere. One filler alloy developed
for use within a specific corrosive environment, is the 5654 alloy. The 5654 alloy
was developed to weld storage tanks that contain hydrogen peroxide. The difference
in alloy performance can vary based upon the type of exposure. Filler alloy charts
ratings are typically based on fresh and salt water only. Corrosion resistance
can be a complex subject when looking at service in specialized high corrosive
environments, and may necessitate consultation with engineers from within this
specialized field. Good contact Alcotec.
Temperature: Stress corrosion cracking (SCR) is an undesirable condition which
can result in premature failure of a welded component. One condition which can
assist in the development of SCR is Magnesium segregation at the grain boundaries
of the material. This condition can be developed in the Mg alloys of over 3 %
through the exposure to elevated temperature. When considering service at temperatures
above 150 Deg F, we must consider the use of filler alloys which can operate at
these temperatures without any undesirable effects to the welded joint. Filler
alloys 5356, 5183, 5654 and 5556 all contain in excess of 3 % Mg, typically around
5%. Therefore, they are not suitable for temperature service. Alloy 5554 has less
than 3 % Mg and was developed for high temperature applications. Alloy 5554 is
used for welding of 5454 base alloy which is also used for these high temp applications.
The Al Si (4xxx series) filler alloys may be used for some service temperature
applications dependent on weld performance requirements. More info contact Alcotec.
Match After Anodizing: The color of an aluminum alloy when anodized depends
on its composition. Silicon in aluminum causes a darkening of the alloy when chemically
treated during the anodizing process. If 5% silicon alloy 4043 filler is used
to weld a 6061 application, and the welded assembly is anodized, the weld becomes
black and is very apparent. A similar weld in 6061 with 5356 filler does not discolor
during anodizing, so a good color match is obtained.
Weld Heat Treatment: Typically, the common heat treatable base alloys, such
as 6061-T6, lose a substantial proportion of their mechanical strength after welding.
Alloy 6061-T6 has typically 45,000 PSI tensile strength prior to welding and typically
27,000 PSI in the as-welded condition. Consequently, on occasion its desirable
to perform post weld heat treatment to return the mechanical strength to the manufactured
If post weld heat treatment is the option, it is necessary
to evaluate the filler alloy used with regards to its ability to respond to the
heat treatment. Most of the commonly used filler alloys will not respond to post
weld heat treatment without substantial dilution with the heat treatable base
alloy. This is not always easy to achieve and can be difficult to control consistently.
For this reason, there are some special filler alloys which have been developed
to provide a heat treatable filler alloy which guarantees that the weld will respond
to the heat treatment.
Filler alloy 4643 was developed for welding the
6xxx series base alloys and developing high mechanical properties in the post
weld heat-treated condition. This filler alloy was developed by taking the well-known
alloy 4043 and reducing the silicon and adding .10 to .30 % magnesium. This chemistry
introduces Mg2Si into the weld metal and provides a weld that will respond to
Filler alloy 5180 was developed for welding the 7xxx series
base alloys. It falls within the Al-Zn-Mg alloy family and responds to post weld
thermal treatments. It provides very high weld mechanical properties in the post
weld heat-treated condition. This alloy is used to weld 7005 bicycle frames and
will respond to heat treatment without dilution of the thin walled tubing used
for this high performance application. Other heat treatable filler alloys have
been developed including 2319, 4009, 4010, 4145, 206.0, A356.0, A357.0, C355.0
and 357.0 for the welding of heat treatable wrought and cast aluminum alloys.
Hardening is used to produce strain-hardened tempers in none-heat treatable
alum alloys. (Increases strength). This is influenced by mechanical energy leading
to deformation. As the deformation occurs the alum alloy becomes stronger, harder
and less ductile.
Hardening (artificial aging). Precipitation heat treat precedes solution heat
treat. Hold alloys at a specific temp long enough to allow constituents to enter
into solid solution, then cool rapidly to hold constituents to remain in solid
solution Artificial aging follows.The alloy is reheated to a lower temp and holding
for a specific time. This heat treat produces superior mechanical properties.
Please note on the heat treatable alloys that have undergone this treatment, the
weld metal heat will change the mechanical properties in both the HAZ and base
Filler Metal Information:
/ Germany A199.5
| || |
Pacweld 421 AA
99% - Mn0.05 Cu 0.05 - 0.2|
Si - Fe0.95
643 to 657C
1100 - H12
| || || |
1100 - H14
| || || |
filler 1100 used to weld all 1XXX alloys plus 3003
and 5005 alloys
Si 0,06, Fe 0.06
Zn 0.03. Ti0.01
| || |
A 92319 |
used for Al lithium aircraft alloy 2090
2319 is heat treatable
good strength ductility on Al Cu Casts
don't use 2319 on 5XXX
5.8 - 6.8|
Si 0.2 / Fe0.3
Ti 0.1 -
543 to 643C
2319 used on 2219 2014
plus alum copper cast alloys
use on 5XXX
TIG - MIG ALUMINUM ELECTRODES.
4043 - 4047
Moderate strength good corrosion resistance.
(Less strength than
ER 4043 - 4047 Low sensitivity to cracking while welding
- 4047 Lower weld ductility than 1XXX - 2XXX - 5XXX
ER 4043 - 4047 Can weld
1XXX - 3XXX - 6XXX 2014 / 2219 / 005 /5052 / 7005 /
7039 Al - Si and Al -
Si - Mg casts
ISO S - ALSi5
France A- S5
use to weld high Mg 5XXX 5083 - 5086- 5456
Century 331 400
4.5 - 6|
Fe 0.8, Cu 0.3
Mg 0,05, Zn 0.1
strength good corrosion resistance
sensitivity to cracks while welding
ductility than 1XXX
use on 1XXX
Al-SI + Al Si Mg casts
4043 - 18
| || || |
thin alum sheet 4047 is used as an alternative to 4043
11 - 13|
Fe 0.8, Cu 0.3
Mn 0.15, Mg 0.1
Moderate strength good
Low sensitivity to cracks while welding
ductility than 1XXX
use on 1XXX
Al-SI + Al Si Mg casts. Faster feeeze than 4043 can prevent formation
of crater cracks
9.3 - 10.7|
Cu 3.3 -4.7
Low sensitivity to weld
cracks on 2XXX
Al - Cu
Al -Si- Cu
cast alloys responds to heat treat
repalce 4043 4047 will result in lower ductility
4145 Low sensitivity to weld cracking on 2XXX alloys|
ER 4145 Good for Al -
Cu Al Si Cu Cast Alloys. Responds to heat treat. ER 4145 Can replace ER 4043 4047,
will however have lower ductility.
3.6 - 4.6|
Fe 0.8, Cu 1.1
Mg 0.1 - 0.3
Zn 0.1, Mn 0.05
573 to 635C
is a goodchoice for the welding of heat-treatable alloys especially the 6XXX series.
4043 has a lower melting point and more fluidity than the 5XXX series filler alloys.
4043 has good welability. 4043 wires are also less sensitive to weld cracking
with the 6XXX series base alloys. 4043 is suitable for sustained elevated temperature
service, above 150 deg F (65 deg C).|
THE ALUM CLEAN BEFORE WELDING. Aluminum
has a great affinity for hydrogen, which can be picked up from many sources, dirt,
paint, moisture, markers, lubricants, etc. All mentioned can form hydrocarbons
causing serious porosity which can weaken the weld.
POROSITY IS MORE OF A CONCERN WITH ALUMINUM THAN IT IS WITH STAINLESS OR STEEL.
THE REASON STAINLESS AND CARBON STEEL TYPICALLY HAVE MUCH GREATER YIELD STRENGTH.
To clean aluminum, consider degreasing solvents and clean stainless steel
brushes. Caution some grinding wheels will contaminate aluminum, (use wheels recommended
for alum). Also on heat treatable alloys, plasma gouging and cutting can cause
micro cracks on component edges, (remove edges with grinder)
5XXX Higher strength than other aluminum electrodes
ER 5XXX used to weld 5XXX
- 6XXX - 7005 alloys
Don't use ER5XXX filler on 2XXX alloys
ER 5XXX Higher
Mg Higher strength and crack sensitivity decreases
ER 5XXX Pre heat and interpass
max temp 150F 65C
| || || || |
| || || |
| || || |
4.3 - 5.2|
Mn 0.5 -1
Cr 0.05 -0.25
579 TO 637 C
use on high temp applications|
5183 is for welding high magnesium alloys to
meet higher tensile strength requirements than 5356.
Use on 5083 and 5654
base materials when required tensile strengths are >40,000 psi (276 MPa) or
greater. Typical applications are in the marine and cryogenic industries, and
high strength structural aluminum fabrication.
REDUCE THE ALUMINUM
black soot that frequently occurs with MIG aluminum welds, is a combination of
aluminum and magnesium alloys that combine with oxygen and form oxides that appear
black. The oxides that form have a lower boiling point than the arc temperature,
they evaporate and condense on the weld or HAZ area. Expect more soot from higher
magnesium alloys. For example the common 5356 filler metal can provide more soot
than E4043 filler metal.
Excess soot is usually an indication of
weld porosity issues. The soot can caused and corrected by the following.
WELD ENERGY. TO ASSIST IN THE REMOVAL OF THE ALUM SURFACE OXIDES. INCREASE WELD
CURRENT / WIRE FEED OR DECREASE WIRE SIZE FOR MORE CURRENT DENSITY.
ARC LENGTH THAT IS TOO LONG. INSUFFICIENT PLASMA ARC ENERGY CONCENTRATION FOR
THE SURFACE OXIDE REDUCTION.
REDUCE THE ARC LENGTH BY LOWERING WELD VOLTS.
[C] INCORRECT WELD GUN ANGLE. ENSURE THE FOREHAND (PUSH) TECHNIQUE IS USED
TO DIRECT THE ARC TO BREAK UP THE ALUM OXIDE SKIN IN FRONT OF THE WELD. BACK HAND
(PULL) WILL PROVIDE THE WORST RESULTS.
[D] INSUFFICIENT GAS COVERAGE.
USE 40 TO 60 CUFT/HR AND ENSURE THE GAS CUP IS A LITTLE WIDER THAN THE WELD AND
HEAT AFFECTED ZONE WIDTH. IF USING HELIUM ENSURE HELIUM FLOW METER IS USED AND
ENSURE HELIUM FLOW RATE IS A MINIMUM OF 45 CUFT/HR
[E] WELD SPEED TO
FAST. MAY NOT ALLOW ADEQUATE BREAKUP OR REMOVAL OF ALUMINUM SURFACE OXIDES.
[F] ALUM SURFACE CONTAMINATED. NEEDS CLEANING.
[G] CYLINDER GAS
CONTAMINATED, TYPICALLY DUE TO POOR DISTRIBUTOR GAS FILLING PRACTICE WHICH LEAVES
EITHER CO2, OXYGEN OR MOISTURE IN THE CYLINDERS.
France S - AlMg5|
ESAB OK 18.15
4.5 - 5.5|
Ti 0.06 - 0.2
/ Fe 0.4
Dont use on high temp
applications. 5356 is a great general purpose filler alloy designed for the welding
of 5XXX series alloys when <40,000 psi (276 MPa) tensile strength is required.
and 5556 sometimes used as an alternative to 5356
| || || || |
Mg 2.4 - 3
601 to 646C
| || |
ESAB OK 18.6
4.7 - 5,5|
Si 0.25, Fe0.4
Mn 0.5 - 1
Cr 0.05 -0.2
Ti 0.05 -0.2
5556 weld deposits will
provide matching tensile strengths for the 5XXX alloys, such as 5083 and 5654.
Contains increased amounts of magnesium and manganese. Dont
use on high temp applications
3.1 - 3.9|
Ti 0.05 -0.15
use on high temp applications|
WELD TIPS AND DATA:
THIS ALUMINUM MIG WIRES A BARGAIN.
you get your aluminum MIG wire at a bargain price, its likely you will have weld
consequences. To test an aluminum MIG wire, take two 1/4 alum plates, six inches
long. Start a 3/16, horizontal fillet weld approx. one inch from the end of the
plate. Make the weld is four inches long. Don't weave use fore hand. After the
weld has cooled, put welded plate in vice and use hammer to fold the plates in
on the weld.
contrast to steel welds, a good, alum weld with proper side wall fusion should
break in most cases in the weld metal. Examine the broken weld surface for porosity.
Clean looking, small pore porosity is found in the best of aluminum welds. Blackish
looking small porosity often results from lubricants from the material surface.
Small gray, oxidized weld porosity often results from air trapped in the joint
or oxygen from the gas cylinders or lines. Extensive shiny porosity may be an
indication of moisture pickup. Ensure synthetic impermeable hoses are used for
your aluminum MIG gas delivery rather than neoprene or rubber hoses.
porosity can be blamed on many materials that can contaminate both the weld wires
and base metals. With aluminum, hydrogen is the prime cause. The bottom line keep
the plates clean and at the ambient shop temperature. If necessary for your application
grind the weld edges. Provide a protective cover for the alum weld wires. When
the weld wires are not in use store in clean dry area. Good manufacturers of aluminum
MIG wires will use extensive manufacturing controls to ensure you have a clean
consistent MIG wire. There is a price to be paid for this weld wire quality. Compare
your bargain priced aluminum wire with a quality and consistent product from a
company like Alcotec.
Oxidation, Hydrogen and Porosity.
has a high maximum solubility for hydrogen atoms in the liquid form and a low
solubility at the solidification point.
Hydrogen dissolved in the liquid
weld metal will try to rise out of the weld during the aluminum solidification.
Some hydrogen gas pores will be trapped and porosity will occur.
combines with oxygen to form an aluminum oxide layer. This micro surface layer
will form instantaneously if the oxide is removed by machining or grinding. The
oxide layer is porous and can easily trap moisture, oil, grease and other materials.
The aluminum oxide layer provides excellent corrosion resistance, but must be
removed before welding as it prevents fusion due to its much high melting point
point than the aluminum alloy .
Arc polarity, plasma molecular action,
mechanical cleaning, solvents and chemical etching are all used to attack the
oxide layer. When MIG welding if the layer is not removed sufficiently a black
soot will appear either side of the weld. To eliminate the soot, first try to
lower the arc length (voltage) as this makes the MIG plasma more dense which provides
a more concentrated plasma cleaning action.
majority of aluminum weld porosity results from entrapped hydrogen gas in the
weld pool. Hydrogen is highly soluble in molten aluminum. Hydrogen can be derived
from many sources.
[a] Hydrogen from base metal contaminates, hydrocarbons,
lubricant, oils dirt, grease, moisture, paints and compressed air and contaminates
from pneumatic cleaning tools or cleaning brushes.
[b] Hydrogen from
lubricant contaminates on the alum weld wire surface.
[c] Hydrogen from
moisture, water leaks in water cooled torches. Water from the gas cylinders. Water
from the porous, hydrated, alum oxide layer on the base metal surface.
Hydrogen that results from high humidity, condensation on parts and weld wires.
[e] Hydrogen that results from contaminates from grinding wheels.
To minimize hydrogen and weld porosity
potential consider, cleaning, degreasing, stainless wire brushes or carbide wheels
to remove the oxide surface. Remember you can always find porosity in the alum
weld, the real question is how much is acceptable and what inspection and weld
process control method will be used to control the porosity.
reduce aluminum weld porosity potential, slow down the weld solidification rate
to allow the hydrogen to exit. Reduce alum weld porosity with the following 11
To remove the alum surface oxide consider a die grinder (>30,000-rpm) rotary,
coarse carbide file. An effective cleaning solution is acetone, beware highly
Increasing weld parameters, with MIG increase the wire feed rate.
Increase weld size.
 Slow down weld travel speed.
Use smaller diameter MIG wires.
 Evaluate the weld procedure so that
weld heat and weld sequence is used as a tool for porosity reduction.
 Use lowest possible MIG weld voltage. Low weld voltage results in short arc
lengths which create more energy in the arc plasma providing improved arc cleaning
action of the surface alum oxides.
Use a higher energy gas mix like
60 helium - 40 argon. The helium requires higher weld voltage. The 60 helium mix
is superior to the common 75 helium 25 argon mix, as the the higher argon content
helps stabilize the arc and provides superior weld cleaning action.
Don't use MIG wire wipes clipped on the wire.
 Don't use anti spatter
within 2 inches of the weld. If you know how to set a weld you would not use anti-spatter.
you are teaching your self, or providing weld process control training for others,
the following resources are the key to attaining MIG and flux cored weld process
The Book: "A Management & Engineers Guide To MIG
Quality, Productivity & Costs"
2. A unique robot
MIG training or self teaching resource.
Robot MIG Welds from Weld Process Controls".
unique MIG training or self teaching resource.
Manual MIG Weld Process Optimization from Weld
A unique flux cored training or self teaching resource.
"Optimum Manual and Automated Flux Cored Plate and
de Soldadura MIG Manual"
(MIG Made Simple. Self teaching in Spanish)
Self Teaching MIG Book/ Video. (MIG
Made Simple in English).
Items 2-3-4 are the most comprehensive process control,
self teaching and training programs ever developed..
Ed's MIG / flux cored process control books and CD training
TIG WELDING ALUMINUM Section 2.