Ed's Aluminum. MIG Weld Facts and Weld Advice.
With welding aluminum or steels and utilizing CV MIG equipment, USING SPRAY TRANSFER AND MIG WELD PROCESS CONTROL EXPERTISE, THE BOTTOM LINE YOU WILL ON MOST WELDED PARTS > 3 mm, ATTAIN SUPERIOR WELD FUSION AND LESS WELD POROSITY
THAN FROM THE WELDS MADE WITH THE MORE COSTLY, LESS DURABLE PULSED MIG WELD EQUIPMENT.
ROBOTS AND ALUMINUM... In the nineteen nineties, Ed set the first
"multi-robot robot cell line" utilized in North America to weld a large volume, large aluminum frame fabrications. Take a look at the above photo of ABB robots welding aluminum golf cart frames. Note my robot aluminum welds were made without the need for push-pull guns.
What's difficult about MIG welding an aluminum goff cart frames using multi-robots in a single cell?
Think of all the issues from the aluminum wire feedability to the common MIG wire burn backs. Alsi the weld joint deviations to the thin aluminum weld burn through concerns. There are many things that will go wrong with in an aluminum robot cell, and once a robot is down, the other robots would have to stop producing the aluminum frame welds,
Over a decade later, in contrast to more than 80% of the robots in the auto industry welding
simple "carbon steel" parts, the four robots I set welding aluminum frames have achieved
much greater robot weld production efficiency, with superior weld quality and less weld rework. In 2104, both the robots and the MIG weld equipment have far surpassed the weld
needs of all of today's applications, with this in mind, few robots will daily, consistently meet their weld quality and production potential. The solution is a simple one, utilize my MIG process control training resources.
Weld process controls are the key
to all sucessful weld applications.
set the multi-robot cell MIG welds on the above aluminum golf cart frames, and also later worked as the weld manager at the Philadelphia Naval ship yard, (back ground). At the ship yard he trained the welders on how to optimize their flux cored welds used in the construction of oil tankers. He saved the ship yard millions of dollars in annual weld rework reductions and increase in hourly production.
A PRIME ISSUE WITH THE COMPLEX, ROBOT, ALUMINUM, GOLF CART APPLICATION WAS THAT PUSH PULL GUNS WERE NOT ALLOWED FOR THE SOFT WIRES AND THEREFORE ALUMINUM WIRE FEED ISSUES AND WIRE BURN
BACKS TO THE CONTACT TIPS WERE A MAJOR CONCERN:
TO GET THEIR ROBOT LINE CONTRACT, CLUB CAR REQUIRED THAT
ROBOT COMPANIES PERFORM A WELD TEST THAT REQUIRED A ROBOT PROVIDE 10,000 ARC STARTS ON ALUMINUM SHEET METAL. THE TEST DID NOT ALLOW MORE THAN 10 WIRE BURN BACKS
OR 10 WIRE FEED ISSUES WITH THE 0.046 (1.2 mm) ALUMINUM WIRE.
FOR THE THIN ALUM FRAME WELDS, ED SELECTED
THE BEST PULSED MIG EQUIPMENT AVAILABLE IN THE 1990s, AN OTC UNIT, THIS IS STILL ONE OF THE
BEST PULSED UNITS AVAILABLE IN 2014. ED COMPLETED THE ROBOT MIG ALUMINUM ARC START WELD
TEST WITHOUT A SINGLE WIRE BURN BACK.
ED AND THE HIGHLY QUALIFIED ABB ROBOT TEAM AT FORT COLLINS CO, USED
ABB ROBOTS, A TRADITIONAL MIG GUN (NO PUSH PULL), AN OTC POWER SOURCE, AN ALCO
TECH WIRE FEED DEREELER, HARD PLASTIC LINERS. AND OF COURSE ED USED HIS WELD BEST PRACTICE - PROCESS CONTROL EXPERTISE TO SET THE ROBOT WELD PROGRAMS.
was the weld manager for ABB Robotics Div. Fort Collins. CO.
production efficiency is greatly influenced
when you have robots working
one robot has a weld issue, the other 3 will not
1990s: MORE ON THE ALUMINUM GOLF CART FRAMES:
MULTI ROBOTS IN A SINGLE CELL - WELDING THIN ALUMINUM - NO PUSH PULL GUN FOR THE SMALL ALUM WIRE - POOR WELD JOINT FIT & OVERSIZED WELD GASPS - TYPICAL WELD HEAT BUILDUP CONCERNS THAT INCREASE WELD BURNTHROUGH POTENTIAL.
When this job came through the door, I was the robot
weld manager for ABB robotics. The robot application required four robots working together in a
single welding a complex, thin gage, aluminum golf cart frame.
Club Car was concerned that with the typical
aluminum wire feed and arc start issues with aluminum MIG welds, that four robots working
together involved a large 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 start test data to ensure
no weld start issues and after 10000 arc starts without a single burn back or arc
ignition issue, the customer was satisfied. I then established the MIG robot alum welds to compensate for the aluminum gage heat build up, the frame part fit issues and and the weld gaps. Each of the four ABB robots produced approx. 30 to 40 welds per-frame.
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 engineers incorporated their Bulls Eye system. The Bulls Eye automatically adjusts the Tool Center Point program for the MIG guns, eliminating
the need for touchups and minimizing down time
 The ABB system also
provided automatic error-handling capability, this was a necessary feature when robots are
in close proximity and the robots had to complete > 120 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
can check the problem.
four robots to weld simultaneously on a small frame application was a challenge
easily handled by the ABB engineers. 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 with hard plastic liners.
 To reduce the wire feed tension which would have influenced wire feed burn back, we utilized Alco Tech Alum Wire Dee-Reelers
aluminum robot production began in early 1998. Since that time, the company has
produced well over 150,000 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.
WE ARE FOOLISH IN ENGINEERING IF WE DON'T LOOK BACK BEFORE WE GO FORWARD:
IRRESPECTIVE OF THE "NEW" WELD APPLICATIONS BEING WORKED ON IN 2014. IT'S LIKELY SOMEONE IN THE PAST THREE DECADES HAS PRODUCED THE WELD
RESULTS THAT WILL BE REQUIRED. I WROTE THE FOLLOWING IN 1989 IN A WELD REPORT I PROVIDED TO A CATERPILLER PLANT.
IN MIND, THAT MANUAL MIG WELD SKILLS HAVE LITTLE TO DO WITH ROBOT - AUTOMATED MIG WELD QUALITY AND PRODUCTIVITY.
WHILE IN CONTRAST, MIG WELD PROCESS CONTROL - BEST PRACTICE KNOWLEDGE
WILL OVERCOME YOUR MOST COMPLEX AUTOMATED WELD CHALLENGES.
Ed Craig 1989
/ ABB Arcitec Pulsed Weld Issues.
How Ed resolved the Robot
Pulsed MIG weld
issues on the
6061 Aluminum Car Seats.
2000, I was requested by an engineer at VAW. This company is a tier one supplier. VAW wanted me to analyze the
weld performance of their new ABB robot and ESAB Arcitec welding equipment. The VAW
plant produces extruded aluminum parts. The aluminum parts were made into car seats for
Ford. The car seats and parts required small robot 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 is the rest of the Alum Welding Story.
are more than 400 wrought aluminum alloys,
and over 200 aluminum alloys in
the forms of castings
and ingots registered with
the Aluminum Association.
Aluminum Alloy Designations have 4 digits.
is alloyed with a number elements to provide improved weldability, strength and
corrosion resistance. The
primary elements that alloy with aluminum are;
This weld energy - profile indicate an
optimum Alum Weld.
The optimum aluminum MIG weld is shown in above picture. Note the weld energy, the resulting weld fluidity, the freeze lines, the weld uniformity, and the lack of scalloped weld edges .
In contrast, as indicated below, many weld shops that produce aluminum welds promote the myth that a good alum weld will show with MIG welds, the pulse fast freeze effects or the TIG intermittent wire feed which produces a similar effect. These colder alum welds will create scalloped weld edges, and if a macro is taken, it will in contrast to the weld above, reveal either lack of fusion or inconsistent weld fusion. Also remember that the faster the alum weld freezes the greater the potential for weld porosity.
Freeze lines may look neat on a bike, but weld process control persons
are aware they don't help with obtaining optimum, consistent weld fusion.
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 approx.
2 - 10% provides strength and allows precipitation hardening. Watch
for weld solidification cracking
Alu-Manganese. 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. Increases strength
none heat treatable
Creates a unique
compound magnesium silicide Mg2Si. Allows special heat treat properties, suitable
for extrusion components
18 - 58 ksi
Alu- Zinc. 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.
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
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.
Heat Treatable 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
alloys used to join Non-Heat-Treatable alloys typically come from three alloy
used 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.
procedure 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.
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.
1xxx, 3xxx, and 5xxx series wrought aluminum alloys are Non-Heat Treatable
and are strain hardenable only.
The Heat Treatable alumumin 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.
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
MIG and TIG heat affected weld zones (HAZ) and the base metal affected by
the weld heat can be significant.
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.
Aluminum alloys can be classified by a temper designation.
O = Annealed,
T = Thermally treated,
F = As fabricated,
H = Strain hardened;
W = Solution heat-treated which can designated both heat treatment, or cold
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.
Some times with "thin" aluminum parts, you need to see freeze lines and scalloped edges to avoid weld burn through as indicated below.
On alum parts > 4mm you wil get better weld results if your welds provide higher weld energy and look more like MIG spray welds.
As the above alum box welds are out side, gage corner welds, the number one issue will be weld burnthrough. These welds will benefit from the pulsed MIG modes in which the weld drops cause rapid freeze welds with distinct paterns as provided above. Also with manual TIG, the welder dipping their wire in and out of the weld pool creates the same effect. Remember this weld appearence may indicate lack of weld fusion or excess porosity when the alum parts > 4 mm thick.
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.
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
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.
3XXX. 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.
4XXX. 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.
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
Series. 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.
& 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.
6xxx 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.
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 5XXX fillers.
7xxx 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.
8XXX. 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.
|Again the above alum welds look neat and many alum welders like this look,
however it does not matter if its a MIG steel or aluminum weld, with welds that have freeze lines like this, weld fusion is questionable and weld porosity potential is increased especially on aluminum parts that are > 4 mm thick.
Weld Equipment Issues,
lack of aluminum welding process expertise:
company I visited was welding 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.
problem robot welds were short lengths, 5/8 to ¾ long (5 to 18 mm) . The robot welds
were 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 different parts, some welds look
very fluid while other welds look very cold. Most of the welds ended up with a black
and dirty appearance yet the push gun angle were 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.
|Optimum balanced wave TIG weld made above on thin alum part. Rememeber with aluminum we have one set of weld concerns with parts < 3 mm (burnthrough) and on parts > 4 mm we have weld fusion and porosity concerns that are reduced with higher energy welds..
Aluminum Weld 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.
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 that are most susceptible to porosity. 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
The trapped hydrogen can result in extensive weld porosity which can often be extensive
cracking is common with low alloy carbon steels but hydrogen cracking will not occur with
aluminum. Hot cracking or solidification
cracking is a primary cause for aluminum cracks.
Aluminum solidification cracks.
As we are all aware aluminum is much weaker than steel and has a much lower weld solidification temperature. These cracks typically occur due to thermal expansion and contraction. The resulting stresses may tear 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.
Aluminum and Liquation Cracking. In
contrast to hot cracking which occurs in the weld, while MIG or TIG welding aluminum
liquation cracking will occur in the welds's heat affected zone (HAZ).
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
How do you define a quality weld?
The influence of the aluminum
oxide layer. Aluminum
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 being so thin its difficult to measure, can also be very porous.
The aluminum oxide layer like a sponge can 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 is a layer
that must be removed for optimum weld quality. Due to its higher melting
point (3700 degrees F) the oxide layer if not removed can decrease the weld fusion. The oxide layer is removed during the weld with the fore hand (push) technique. During the forehand weld travel, the gas molecules in the arc plasma collide with the oxide surface moving the oxides. The oxides are
also disrupted through mechanical cleaning, wire brushing, solvents and chemical etching. The weld voltage
control also influences the oxide removal. One of the best practices to attain clean
alum MIG welds is to "use the lowest possible open arc voltage". The low voltage assures a short arc
length, that results in a concentrated arc plasma which assists in the oxide removal.
alloys that are difficult to weld or sensitive to cracking.
that may be sensitive to hot cracking are found in the 2xxx series, alum-copper, and in the 7xxx series, alum-zinc.
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.
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.
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?
Ensure you ask the right filler metal
the best alum filler for "corrosion resistance"?
What's the best alum filler to "match the color" of the base metal?
the best alum filler for carrying "high weld current"?
What's the best alum filler for "good weld crack
What's the best alum filler for the "desired
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?
4043aluminum 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
 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 base alloys.
 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.
5356wire 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.
following 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
 excess preheating,
 slow weld
 wide (8 mm) weld weaves,
 oversized welds,(>6 mm fillets),
 welding thin parts or many welds concentrated is a small area,
unnecessary 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.
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
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.
Ductility 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 qualification.
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.
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 component.
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.
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 heat treatment.
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 metal.
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
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
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.
4643 heat treatable.
Similar results to 4043.
3.6 - 4.6
Fe 0.8, Cu 1.1
Mg 0.1 - 0.3
Zn 0.1, Mn 0.05
573 to 635C
||4643 and 4043
provide similar results.in the as welded condition. Used for heavy sections, multipass welds but minimize weld dilution
These wires are a
good choice for the welding of heat-treatable alloys especially the 6XXX series.
These wire will have a slightly lower melt point and provide more fluidity than the 5XXX series filler alloys.
4043 will have good welability and are 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 OXIDES"
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.
[A] INSUFFICIENT 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.
[B] 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
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 CONTAMINATED. NEEDS CLEANING.
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
Ed's MIG / flux cored process control books and CD training resources.
Whats in Aluminum Section Two..?
OTC Daihen or Fronius weld equipment for those aluminum welds?
Robot aluminum arc start data.
Welding aluminum bus bars.
Reduce aluminum crater cracks.
Aluminum gas mix selection made simple.
Aluminum stress corrosion cracking.
6061 Aluminum weld issues.
6061 weld distortion issues.
Aluminum Spray Transfer Parameters.
How much aluminum wire is required per-weld.
Aluminum wire feed to weld deposition.
The best aluminun wire size.