mig welding aluminum tips

5/27/2018 MIG Welding Aluminum Tips

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MIG Welding Aluminum Tips.

OLD MIG WELD TECHNOLOGY WITH MIG PROCESS CONTROL EXPERTISE, OFTENPROVES TO BE MORE BENEFICIAL THAN NEW ROBOTS AND SOPHISTICATED WELDEQUIPMENT TECHNOLOGY APPLIED WITHOUT WELD PROCESS CONTROL

EXPERTISE.

In the nineteen nineties, Ed set the first "multi-robot robot cell" line in North America, toweld a large aluminum application. Take a look at the above photo of ABB robotswelding aluminum golf cart frames. Note these aluminum welds were made without puspull guns..

What is difficult about welding an aluminum goff cart frame using multi-robots in asingle cell? Think of all the issues from wire feedability to wire burn backs, from weld

joint deviations to weld burn through concerns that can go wrong with a single robot.Once that single robot is down, the other robots have to stop producing the aluminumframe welds,

Over a decade later, in contrast to more than 80% of the robots in the auto industrywelding simple "carbon steel" parts, the four robots I set welding aluminum frames haveachieved much greater robot weld production efficiency, superior quality and less weldrework.

Today both the robots and the MIG weld equipment have far surpassed the weldingneeds of all of today's applications, with this in mind, yet few robots meet their weldquality and production potential. The solution is a simple one utilize myMIG process

control training resources.
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Ed set the robot welds on this alum golf cart frame and also trainedthe ship yard welders on flux cored welding for these oil tankers built at thePhiladelphia Naval Yard.

1990s: A GREAT CONCERN WITH THE ALUMINUM GOLF CART APPLICATION THAT

DID NOT UTILIZE PUSH PULL GUNS WAS WIRE FEED ISSUES AND WIRE BURN BACKSTO THE CONTACT TIPS:

TO GET THEIR ROBOT LINE CONTRACT, CLUB CAR REQUIRED THAT ROBOTCOMPANIES PERFORM A WELD TEST THAT REQUIRED A ROBOT PROVIDE 10,000ARC STARTS ON ALUMINUM SHEET METAL. THE TEST DIDNOT ALLOW MORE THAN 10 WIRE BURN BACKS OR 10 WIREFEED ISSUES USING AN 0.046 ALUM WIRE.

USING THE BEST PULSED POWER SOURCE (OTC)AVAILABLE) IN THE 1990s AND STILL ONE OF THE BESTPULSED UNITS AVAILABLE IN TODAY, ED COMPLETED THEROBOT MIG ALUMINUM ARC START WELD TEST WITHOUT ASINGLE WIRE BURN BACK.

WITH THIS COMPLEX APPLICATION ED WAS WORKING WITHTHE HIGHLY QUALIFIED ABB ROBOT PERSONNEL IN FORTCOLLINS CO. USING ABB ROBOTS, A TRADITIONAL MIG GUN (NO PUSH PULL), ANOTC POWER SOURCE, AN ALCO TECH WIRE FEDD DEREELER, HARD PLASTICLINERS AND OF COURSE AT THAT TIME HE APPLIED HIS 35 YEARS OF MIGWELDINGBEST PRACTICES - PROCESS CONTROL EXPERTISETO THE ROBOT WELDPROGRAM.
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Note Ed was the senior weld engineer / weld mgr for ABB Robotics Div. Fort Collins. CO.

Weld production efficiency can be greatly influencedwhen you have robots working together

When one robot has a weld issue the other 3 will not be working.

1990s: MORE ON THE ALUMINUM, GOLF CART FRAME APPLICATION:

CONCERNS: MULTI ROBOTS IN A SINGLE CELL - WELDING THIN ALUMINUM - NOPUSH PULL GUN FOR THE SMALL ALUM WIRE - POOR WELD JOINT FIT & OVERSIZEDWELD GASPS - TYPICAL WELD HEAT BUILDUP CONCERNS THAT INCREASE WELDBURNTHROUGH 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 acomplex, thin gage, aluminum golf cart frame. Club Car was concerned that with thetypical aluminum wire feed and arc start issues with aluminum MIG welds, that fourrobots 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 nomore than ten arc ignition issues.

I set the initial start test data to ensure no weld start issues and after 10000 arc startswithout a single burn back or arc ignition issue, the customer was satisfied. I thenestablished the MIG robot alum welds to compensate for the aluminum gage heat buildup, the frame part fit issues and and the weld gaps. Each of the four ABB robotsproduced approx. 30 to 40 welds per-frame.


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[] ABB provided an automatic torch alignment system. The ABB system can make 3-Dand angular calculation via its BullsEye automatic TCP calibration system.

[] The ABB engineers incorporated their Bulls Eye system. The Bulls Eye automaticallyadjusts the Tool Center Point program for the MIG guns, eliminating the need fortouchups and minimizing down time

[] The ABB system also provided automatic error-handling capability, this was anecessary 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, itcommunicated the error the other three. The other robots would then finish the weldthey 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 positionwhere an operator can check the problem.

Programming four robots to weld simultaneously on a small frame application was achallenge easily handled by the ABB engineers. Adding to the complexity was the needto program error handling as well as welding. Each group of welds had to have its ownerror handler program, so developers had to keep in mind the path of each robot andmake 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, weutilized Alco Tech Alum Wire Dee-Reelers

The aluminum robot production began in early 1998. Since that time, the company hasproduced well over 150,000 aluminum golf cart frames. Two people operate the system, oneloads a fixture in one cell, while the robots are welding in the other cell. Arc on time for the130 welds on the cart frames was approx. 6 minutes as compared with 27 minutes for thewelders to manually weld the frames.


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WE ARE FOOLS IF WE DONT LOOK BACK: IRRESPECTIVE OF THE"NEW" WELD APPLICATION YOU ARE WORKING ON TODAY. IT'SLIKELY SOMEONE IN THE PAST HAS PRODUCED THE WELDINGRESULTS YOU ARE SEARCHING FOR.

KEEP IN MIND THAT WELD SKILLS HAVE MINIMAL IMPACT ON ROBOTWELD QUALITY AND PRODUCTIVITY. IN CONTRAST, WELD PROCESSKNOWLEDGE AND WELD EQUIPMENT / CONSUMABLE KNOWLEDGEWILL OVERCOME THE GREATEST ROBOT / AUTOMATED WELDCHALLENGES. Ed Craig 1989

ESAB / ABB Arcitec Weld Issues.

Robot Welds on Ford 6061 Aluminum Car Seats.

During 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 Arcitecwelding equipment. The VAW plant produces extruded aluminum parts. The aluminum partswere made into car seats for Ford. The car seats and parts required small robot welds whichwere made on thin gage 6061 aluminum.

Since the installation of the robot cells, continuous production of optimum weld qualityparts has been impossible due to the issues documented in this report. Weld reject rates


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averaged sixty percent and the robot down time per hour averaged 20 to 30 minutes. This isthe rest of theAlum Welding Story.

There are more than 400 wrought aluminum alloys,and over 200 aluminum alloys in the forms of castings andingots registered with the Aluminum Association.

Wrought Aluminum Alloy Designations have 4 digits.

Aluminum Alloying Elements.Aluminum is alloyed with a number elements to provide improved weldability, strength andcorrosion resistance. The primary elements that alloy with aluminum are;

[] copper,[] silicon,[] manganese,[] magnesium,[] zinc.
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Optimum Alum Weld.

The optimum aluminum MIG weld is shown in top picture. Note the weld energy, the resulting weld fluidity,

the weld uniformity and lack of scalloped weld edges .

In contrast, as indicated below, many weld shops that produce alum 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.

Poor Alum Weld


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Aluminum Alloys

First digit is principle aluminum alloy. First digit alsodescribes the aluminum series. Ksi is ultimate tensilestrength range.

1XXX > 99% Aluminumnon heattreatable

10-27 ksi

2XXX

Alu - Copperapprox.2 - 10% provides strength andallows precipitation hardening.Watch for weld solidificationcracking

heat treatable 27-62 ksi

3XXXAlu-Manganese. Providesincreased strength

non heattreatable

16-41 ksi

4XXX

Alu-Silicon. Reduces meltingtemperature, welds more fluid.When combined with magnesiumprovides an alloy that can beheat treated.

Both heattreatable andnone heattreatable

25-55 ksi

5XXXAlu - Magnesium. Increasesstrength

none heattreatable 18-51 ksi

6XXX

Alu Magnesium and SiliconCreates a unique compoundmagnesium silicide Mg2Si.Allows special heat treatproperties, suitable for extrusioncomponents

heat treatable18 - 58ksi

7XXX

Alu- Zinc.When you add zinccopper and magnesium you get aheat treatable alum alloy of very

high strength. Watch for stresscorrosion cracking. Some alloysMIG weldable some not

heat treatable32 -88

ksi


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None Heat Treatable Aluminum Alloys.With these alloys it's possible to increase the alum strength through cold working orstrain hardening. To attain the desired strength, a mechanical deformation must firstoccur in the aluminum structure, the deformation will result in increased resistance tostrain producing both higher strength and lower ductility.

These alloys are different from "heat-treatable alloys" as the non-heat treatable alloyscannot form second-phase precipitates for improved strength. Non-heat-treatable alloyscannot 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 additionsneeded for HEAT TREATABLE precipitation hardening, copper plus magnesium, ormagnesium plus silicon can lead to hot cracking during welding. The heat affected zone(HAZ) mechanical properties are higherin not-heat treatable alloys as the HAZ is notcompromised by coarsening or dissolution of precipitates.

Non Heat Treatablewrought aluminum alloys can be placed into one of four groups,1xxx Al (Al 99% minimum purity)3xxx Al + Mn4xxx Al + Si (some exceptions)5xxx Al + Mg

Filler alloys used to join Non-Heat-Treatable alloys typically come from three alloy groups:

1xxx4xxx5xxx

Commonly used filler alloys for None Heat Treatable alloys include,

1100, 1188,4043, 4047,5554, 5654, 5183, 5356, 5556.

When MIG or TIG welding Non-Heat Treatable aluminum alloys, note that the HAZ will beannealed during the weld. The none heat treatable alloys are annealed during welding in the600-700 F, range, the time required at this temperature is short. The alum welds will haveminimal impact on the transverse ultimate tensile strength of a groove weld as the annealedHAZ of the none heat treatable alum alloys will usually be the weakest area of the weld joint.

Weld procedure qualification for the None-Heat Treat alloys is typically based on theminimum tensile strength of the alum base alloy in its annealed condition.

When 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 bothrecrystallization / grain growth. In contrast with the heat treatable alloys the mechanicalproperties loss is extensive.

Note: When welding all aluminum alloys,please note: To help retain the properties in theAluminum HAZ locations, always use low to conservative TIG or MIG weld parameters, think


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low weld heat. Low weld heat is one of the great real world benefits of using the pulsed MIGweld transfer mode on aluminum applications.

For the None Heat Treatable series that require strength, the 5xxx- alloys are popular forapplications where good joint strengths can be obtained in the as-welded condition withoutthe need for post-weld heat treatment.

The 1xxx, 3xxx, and 5xxx series wrought aluminum alloys are Non-Heat Treatable and arestrain hardenable only.

The Heat Treatable alumumin alloys attain their optimum mechanical properties throughthermal controlled heat treatment.

The 2xxx, 6xxx, and 7xxx series wrought aluminum alloys are Heat Treatable. In contrast the4xxx series consist of both heat treatable and non-heat treatable alloys, beware of hotcracking with some of these alloys.

Heat treatable alloys attain their mechanical properties through thermal treatment. Solutionheat treatment and artificial aging are the most common methods.

Solution Heat Treatmentis the process of heating to temperatures (around 990 Deg. F). Inthis temperature range the alloying elements or compounds go into solution. After heatingthe part is quenched typically in in water. The quench produces a supersaturated solution atroom temperature. Solution heat treatment is usually followed by aging.

Aging. The precipitation of a portion of the elements or compounds from a supersaturatedsolution in order to yield the required properties.

Heat 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-treatis 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 asupersaturated solution. The third and final step in the heat treat process is to maintain thewelded part at a low temperature. The time has to be long enough to allow a controlledamount of precipitation of the aluminum alloying elements.

The 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.

With heat treatable or none heat treatable aluminum alloys, the differences between theMIG and TIG heat affected weld zones (HAZ) and the base metal affected by the weldheat can be significant.

With none heat treatable aluminum alloys in the 1xxx - 3xxx - 4xxx - 5xxxseries, thereduction of the HAZ tensile strength is typically predictable under normal weld conditions.In contrast the HAZ area strength with heat treatable alloys 2xxx - 6xxx - 7xxxcan be reducedbelow the minimum tensile strength required for the parts when the welding heat isexcessive during the weld. Higher tensile strength from the filler and reduced strength fromthe part influenced by the annealing effect of the weld and you have hot cracking in the HAZof the base metal.


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Alum Designations. 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 working aging.

Wrought aluminum alloysare alloys that are rolled from ingot or extruded. Alloys can alsobe divided into a cast group of alloys. Cast alloys are those used to manufacture parts frommolten alloys of aluminum poured into molds. Cast alloys are precipitation hardenable butnever 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. 2xxxdesignates the copper cast alloys.

Some times with thin aluminum parts, with the weld appearence, youneed 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 weldsprovide higher weld energy and look like MIG spray welds.

As thes above alum box welds are out side, gage corner welds, the number oneissue will be weld burnthrough. These welds will benefit from the pulsed MIGmodes in which the weld drops cause rapid freeze welds with distinct paternsas provided above. Also the manual TIG welder dipping the wire in and out of


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the weld creates the same effect. Remember this weld appearence may indicatelack of weld fusion or excess porosity when the alum parts > 4 mm thick.

Cast Aluminum Alloy Designations:

Aluminum 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 version.

First digit of cast aluminum alloys is the principle alloy. Firstdigit also describes the aluminum series.

1XXX 99% Min Alum2XXX Copper3XXX Silicon + Cu and or magnesium4XXX Silicon5XXX Magnesium6XXX Unused Series7XXX Zinc8XXX Tin9XXX Other Elements

Weldable grades of aluminum castings are319.0, 355.0, 356.0, 443.0, 444.0, 520.0, 535.0, 710.0 and 712.0.

Aluminum 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 weldingaluminum. Aluminum has higher thermal conductivity and lower melting temperatures, bothfactors 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 alloyedwith the right elements.


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[] Aluminum can conduct electricity six times better than steel and nearly 30 times betterthan 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 thermalconductivity creates a great heat sink which can create insufficient weld fusion on parts over4 mm and weld burn through issues on parts less than 3 mm. The weld fusion concerns isone 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 getweld fusion with the short circuit mode. Pulsed MIG is beneficial on all thin aluminumapplications. The viscosity is beneficial when using spray or pulsed transfer for all positionwelds.

[] Aluminum has a low melting point 1,200 degrees F, this is more than half that of steel. Fora given MIG wire diameter the transition short to spray weld current for aluminum is muchlower than it is for steel.

Aluminum Descriptions.

1XXX.Minimum 99% aluminum. This very low strength series is considered none-heattreatable and is used primarily for bus bars and some pipe and chemical tanks. This alloyprovides superior corrosion resistance. Alloys with purity levels greater than 99,5% are usedfor electrical conductors (for example alloy 1350). 1XXX series are easily welded with 1100and 4043 alloys.

2XXX.Alu-Copperprovide approx. 2 to 6% Cu with small amounts of other elements. The Cuincreases strength and enables precipitation hardening. The 2XXX series is mainly used inthe aerospace industry. Most of the 2XXX alloys have poor weldability due to their sensitivityto 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 hotcracking. Exceptions to this are alloys 2014, 2219 and 2519, which are readily welded with2319 filler wires. Hot cracking sensitivity in these Al-Cu alloys increases as copper is added

upto 3% and decreases when the copper is above 4.5% Be wary of Alloy 2024 as it iscrack sensitive.

3XXX. Alu-Manganesewhen added to aluminum produces a moderate strength, none-heattreatable series typically used for radiators, cooking pans, air conditioning components andbeverage containers and storage equipment. The 3XXX series is improved through strainhardening which provides improved corrosion properties and improved ductility. Typicallywelded with 4043 or 5356 electrode, the 3XXX series is excellent for welding and not prone tohot cracking. The moderate strength of this series prevent these alloys from being utilized inspecific fabrication or structural applications.


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4XXX. Alu-Siliconreduces melting temperature improves fluidity. The most common useis as a welding filler material. The 4xxx-series alloys have limited industrial application inwrought form. If magnesium added it produces a precipitation hardening, heat treatablealloy. The 4XXX series has good weldability and can be a non-heat-treatable and heattreatable alloy. Used for castings, weld wires. The 4xxx wires are more difficult to feed thanthe 5xxx series.

5XXX.Alu-Magnesiumincreases mechanical properties through solid solutionstrengthening and improves strain hardening potential. These alloys have excellentweldability with a minimal loss of strength. The 5 XXX series has lower tendency for hotcracking. The 5XXX series provide the highest strength of the nonheat-treatablealuminum alloys. These alloys are used for cryo vessels, chemical storage tanks, autoparts, pressure vessels at elevated temperatures, cryogenic vessels as well asstructural applications, railway cars, trailers, dump trucks and bridges because of thecorrosion resistance. 5xxx looses ductility when welded with 4xxx series fillers due toformation of Mg2Si.

5xxx Series and Weld Crack Sensitivity:The 5xxx typically while welding with or withoutfiller metal have low crack sensitivity. Usually the filler metal will have a little more Mg thanthe base metals being welded. Be wary of 5052 especially if TIG welding without a fillermetal, use a high Mg filler like 5356 for the 5052 alloy. All aluminum concave fillet welds andconcave craters are sensitive to hot cracks.

6XXX. Alu-Magnesium & Silicon(magnesium-silicides) combine to serve as alloyingelements for this medium-strength, heat-treatable series. 6XXX are principally used inautomotive, pipe, structural, railings and extrudedparts. This series can be prone to hotcracking, but this problem can be overcome by the correct choice of joint and filler metaland weld procedures that minimize weld heat input. This series can be welded with either5XXX or 4XXX series, adequate dilution of the base alloys with selected filler alloy isessential. 4043 electrode is the most common filler metal for this series. Be wary of liquationcracking 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, thesealloys 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 assufficient 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 squaregroove. All 6xxx aluminum applications that have concave welds and concave craters aresensitive to hot cracks.

7XXX. Alu-Zincwhen added to aluminum with magnesium and copper permits precipitationhardening and produces the highest strength heat-treatable aluminum alloy. These alloysare primarily used in the aircraft industry, armored vehicles and bike frames. The weldabilityof 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.) Andsusceptible to stress corrosion cracking. Grades 7005 and 7039 are weldable with 5XXXfillers.

7xxxCrack 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


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principally used in the aerospace industry. Filler metal selection for these heat-treatablealloys include the 4XXX series.

Again the above alum welds look neat and many alumwelders like this look, however it does not matter if itsa MIG steel or aluminum weld, with welds like this poorweld fusion and increased porosity potential will resulton parts > 4 mm thick.

Panasonic Weld Equipment Issues, andlack of aluminum welding process expertise:


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The company I visited was welding 6xxx series, extruded aluminum, thin gage parts. Theyhad purchased a Panasonic VR OOGAL 11robot, with a Panasonic 350 amp Panastar RA 350pulsed power source. For the welds they used an 0.046, 4043 wire and argon. The MIG wirespool 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 long (5 to 18 mm) . The robot weldswere made on aluminum square tubes 0.070 thick. The 6xxx tubes are welded to a thickeralum part 3/16 thick. Since they purchased the robot the completed welds never lookconsistent over their short lengths. All the thin tube welds were made with the same welddata, yet in the same locations on different parts, some welds look very fluid while otherwelds look very cold. Most of the welds ended up with a black and dirty appearance yet thepush gun angle were correct. These welds caused so many issues the company was readyto 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. Rememeberwith aluminum we have one set of weld concerns with parts < 3 mm
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(burnthrough) and on parts > 4 mm we have weld fusion and porosityconcerns that are reduced with higher energy weld.

Aluminum Welding Tips and Information:

Aluminum alloys can provide unique physical properties.

Weight.Aluminum is three times lighter than steel and yet aluminum can provide higherstrength when alloyed with specific elements.

None Magnetic.Since aluminum is nonmagnetic, arc blow is not a problem duringaluminum welding.

Thermal Conductivity.With a thermal conductivity rate that is five to six times higherthan 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 inall positions with spray and pulsed with relative ease. In contrast to steel the highconductivity of aluminum acts as a heat sink making weld fusion and weld penetrationmore difficult to achieve on parts > 4 mm.. However on thin parts, the rapid build up ofheat in the alum parts can add to high weld fluidity and weld burn through potential.

Aluminum Porosity and Hydrogen.When MIG or TIG weldingaluminum, the weld decision maker should always be aware that


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this is one of the metals that are most susceptible to porosity. The main cause of porosity inaluminum welds is the absorption of hydrogen in the weld pool which forms gas pores in thesolidifying weld metal. The most common sources of hydrogen are hydrocarbons andmoisture from contaminants on the aluminum base metal and on the filler wire surface. Alsowater vapor from the MIG or TIG shielding gas will provide the same results.The trapped hydrogen can result in extensive weld porosity which can often be extensive

Note: Hydrogen cracking is common with low alloy carbon steels but hydrogen cracking willnot occur with aluminum. Hot cracking or solidification crackingis a primary cause foraluminum cracks.

Alum Solidification Cracks. As we are all aware aluminum is muchweaker than steel and has a much lower weld solidificationtemperature. These cracks typically occur due to thermalexpansion and contraction. The resulting stresses may tear the

weld apart..

Common causes of alum solidification cracks.

[a] incorrect choice of alum weld consumable.

[b] Concave welds, undersize welds, and welds with insufficient weld throat. (The weldthroat depth must be sufficient to compensate for the weld contraction stresses).

[c] Weld joints too rigid.

[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 interpasstemperature control.

Note: Solidification cracking is reduced with the selection of crack-resistant filler metal likethe 4xxx and 5xxx filler metal. Be wary when choosing the filler metal to specifically reduceweld cracking, as the weld metal may provide lower strength than the parent metal and willnot respond to heat treatment if applied.

Aluminum and Liquation Cracking. In contrast to hot crackingwhich occurs in the weld, while MIG or TIG welding aluminumliquation cracking will occur in the welds's heat affected zone

(HAZ).

With liquation cracking low melting point films are formed atthe grain boundaries and these films (liquid elements)cannotwithstand the contraction stresses during the weld metalsolidification. Heat treatable alloys, like the 6xxx and 7xxxseries are sensitive to liquation cracking. To reduce thepotential for liquation cracking, consider a weld wire with alower melt temperature than the parent metal. With alloy 6061 -6082, liquation cracking can occur in the partially melted zone


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when a weld with good dilution is made with 5356 or similar filler metal is utilized. In contrastwhen welding the same alloys with 4043 liquation cracking should not occur.

How do you define a quality weld?

The influence of the aluminum oxide layer.Aluminum will combine with oxygen to form analuminum oxide layer. This layer will form instantly as the aluminum surface is ground ormachined. The aluminum oxide layer while being so thin its difficult to measure, can also bevery porous.

The aluminum oxide layer like a sponge can readily trap moisture, oil, grease and othermaterials adding to the potential for hydrogen pickup. The aluminum oxide layer providesexcellent corrosion resistance, however this is a layer that must be removed for optimumweld quality. Due to its higher melting point (3700 degrees F) the oxide layer if not removedcan 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 plasmacollide with the oxide surface moving the oxides. The oxides are also disrupted throughmechanical cleaning, wire brushing, solvents and chemical etching. The weld voltagecontrol also influences the oxide removal. One of the best practices to attain clean alum MIGwelds is to "use the lowest possible open arc voltage". The low voltage assures a short arclength, that results in a concentrated arc plasma which assists in the oxide removal.

Aluminum alloys that are difficult to weld or sensitive to cracking.

Alloys that may be sensitive to hot cracking are found in the 2xxxseries, alum-copper,and in the 7xxxseries, alum-zinc.

With the 2xxx series hot cracking sensitivity increases with Cu < 3% and decreases with


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Cu > 4.5%. Avoid weld practices that promote high heat input as grain boundarysegregation cracking potential.

7xxx alloys that contain Al-Zn-Mg like 7005 resist hot cracking and have bettermechanical weld properties than Al-Zn-Mg-Cu alloys like 7075 that contain smallamounts of Mg and Cu which extend the coherance range increasing the crack

sensitivity. Zirconium is added to refine grain size and reduce crack potential. Electrode5356 is often recommended for this group as the magnesium helps prevent cracking.The 4043 electrode would provide excess Si promoting brittle Mg2Si particles in thewelds.

Be careful when welding dissimilar alum alloys as extending the coherence rangeincreases the crack sensitivity. When welding alloys that do have good weldability likewelding a 5xxx alloy to a 2xxx base alloy or a 2xxx filler on a 5xxx alloy and vice a versayou can end up with high Mg and Cu and increase the coherence range increasing thecrack sensitivity.

Five Common Aluminum, MIG Filler WeldingMetals:

5356 - 4043 - 1100 - 5556 - 4047

Usually the filler metal selected should be similar incomposition to the base metal alloy for example a1XXX filler wire for welding 1XXX - 3XXX-series basemetal alloys. Special consideration is howeverrequired when weldability is an issue. Weldability ofnon-heat-treatable aluminum alloys should be

measured in resistance to hot cracking and porositypotential. Hot cracking issues are encountered whenwelding with alloys sensitive to cracking, alloys subject to excess heat or parts that arehighly constrained.

Cracking issues can occur when low strength weld alloys like 1XXX are used to join 5XXXalloys (or vice versa) or when welding dissimilar metals with different strengths. The bestfiller metals when hot cracking occurs is to use 4xxx fillers.

When considering an aluminum MIG filler metal, make sure you askthe right filler metal questions.

What's the best alum filler for "corrosion resistance"?

What's the best alum filler to "match the color"of the base metal?

What's the best alum filler for carrying "high weld current"?

What's the best alum filler for "good weld crack resistance"?

What's the best alum filler for the "desired strength"?


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What's the best alum filler for "high temp or low temp service"?

Weld mechanical properties such as yield, tensile strength and elongation are affected bythe choice of aluminum base and filler alloys.

With groove welds, the heat affected zone (HAZ) dictates the

strength of the joint.The non-heat-treatable aluminum alloys HAZwill be annealed and their HAZ will be the weakest point.

Heat-treatable alloys require much longer periods at annealingtemperatures combined with slow cooling to completely anneal themso that weld strength is less affected. When welding alum pleaseremember that preheating, excess interpass temperatures and andexcess weld heat from over sized welds, slow weld speeds andweaving all increase temperature and time at temperature all can influence the strengthlevels that will be attained.

In contrast to groove welds the fillet weld strength is dependent on the composition ofthe filler alloy used to weld the joint. For example the selection of 5XXX instead of 4XXX

can provide twice the weld strength.

When to use either 4043 or 5356 filler wire?

4043aluminum filler wire is an aluminum wire with 5% silicon. This wire was developed forwelding the 6xxx series aluminum alloys. 4043 may also be used to weld the 3xxx series or2xxx alloys. 4043 is also used for welding castings.

[] 4043 has a lower melting point and provides more weld fluidity than 5xxx series filleralloys. 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 weldsurface more stable transfer and is also less sensitive to weld cracking when welding the6xxx series base alloys.

[] 4043 provides more weld penetration than 5356, however the 4043 will produce welds withless shear strength and ductility than those made using 5356.


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[] 4043 is used for applications when the service temp above 150 F, in contrast 5356 is notsuited to applications where prolonged heat is applied.

[] 4043 is not well suited for welding Al-Mg 5xxx alloys and should notbe used with 5xxx alloys with > 2.5% Mg, alloys such as 5083, 5086 or5456 as excess magnesium-silicide (Mg2Si) can develop in the weld

structure decreasing ductility and increasing crack sensitivity. (Oneexception to this 4043 rule is when welding the 5052 alloy which has alow 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 shapingthe welded part after welding to remember this fact.

[] For MIG wire feedability note the 4043 or 1100 are softer than 5356 so expect more wirefeed issues.

5356wire is an aluminum wire with 5% magnesium. This is the mostcommon aluminum filler wire due to superior strength, ductility andsuperior MIG wire feedability. 5356 was developed to weld the 5xxxstructural alloys and also the 6xxx series extrusions. Do not use the5356 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 degreesCelsius). The formation of Al2Mg at elevated temperatures at the grain boundaries makes thealloys prone to stress corrosion. For components that will be anodized after welding, 5356 isrecommended for the best color match, in contrast 4043, will turn black when anodized.

Alum Weld Strength and Weld Heat Considerations:

As mentioned, typically the resulting HAZ of a groove weld will determine the strength of thejoint 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.

Heat treatable alloys require a specific time at temperature to fully reduce their strength. Thestrength 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 ofstrength loss due to weld heat is influenced by both time / temperature. Faster weld speed orsmaller welds produce less weld heat in the weld area. Fixtures that provide heat sinks lowerthe weld heat input. The lower the weld heat the higher the as welded strength.

The following can add unnecessary weld heat and require consideration on the influence ofweld heat on aluminum alloys;

[1] lack of interpass weld temperature controls on, multi-pass welds.[2] excess preheating,[3] slow weld speeds,[4] wide (8 mm) weld weaves,[5] oversized welds,(>6 mm fillets),[6] welding thin parts or many welds concentrated is a small area,


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[7] unnecessary high weld current and voltage.

Shear or Tensile Strength.In contrast to aluminum groove welds, thefillet weld strength is mostly dependent on the composition of the alumfiller 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 seriesfiller metals, the tensile strength of groove welds differences may be minimal.Howeverserious consideration is required when considering the shear strength of aluminum "filletwelds". The approx. transverse shear strength of 4043 is around 15 ksi while theshear strength of 5356 is approx. 26 ksi. The bottom line the 5356 provides superior ductilityand shear strength.

WIRE TYPE AND FILLET WELD SIZE: Alcotec reports that tests have shown that a requiredshear strength value in a fillet weld in 6061 base alloy required a 1/4 inch (6 mm) fillet weldwith 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 threerun fillet to achieve the same strength.

Ductility and alum welds may be a consideration if forming is to be performed after weldingor if the alum weld is going to be subjected to impact loading. Also ductility should be givenconsideration when bend tests are applied during weld procedure qualification.

In contrast to the 5xxx series, the 4xxx series filler alloys provide lower weld ductility, this isaddressed with special requirements within the code or standards relating to the weld testsample thickness, bending radius, and material condition.

Corrosion Resistance: Most aluminum base alloy filler alloy combinations providesatisfactory 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 alloywas developed to weld storage tanks that contain hydrogen peroxide. The difference in alloyperformance can vary based upon the type of exposure. Filler alloy charts ratings aretypically based on fresh and salt water only. Corrosion resistance can be a complex subjectwhen looking at service in specialized high corrosive environments, and may necessitateconsultation with engineers from within this specialized field. Good contact Alcotec.

Service Temperature:Stress corrosion cracking (SCR) is an undesirable condition whichcan result in premature failure of a welded component. One condition which can assist in thedevelopment of SCR is Magnesium segregation at the grain boundaries of the material. Thiscondition can be developed in the Mg alloys of over 3 % through the exposure to elevatedtemperature. When considering service at temperatures above 150 Deg F, we must considerthe 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 5554has less than 3 % Mg and was developed for high temperature applications. Alloy 5554 isused for welding of 5454 base alloy which is also used for these high temp applications. TheAl Si (4xxx series) filler alloys may be used for some service temperature applicationsdependent on weld performance requirements. More info contact Alcotec.


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Color Match After Anodizing: The color of an aluminum alloywhen anodized depends on its composition. Silicon inaluminum causes a darkening of the alloy when chemicallytreated during the anodizing process. If 5% silicon alloy4043 filler is used to weld a 6061 application, and the weldedassembly is anodized, the weld becomes black and is veryapparent. A similar weld in 6061 with 5356 filler does notdiscolor during anodizing, so a good color match isobtained.

Post 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-T6has 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 heattreatment to return the mechanical strength to the manufactured component.

If post weld heat treatment is the option, it is necessary to evaluate the filler alloy used withregards to its ability to respond to the heat treatment. Most of the commonly used filleralloys will not respond to post weld heat treatment without substantial dilution with the heattreatable base alloy. This is not always easy to achieve and can be difficult to controlconsistently. For this reason, there are some special filler alloys which have been developedto provide a heat treatable filler alloy which guarantees that the weld will respond to the heattreatment.

Filler alloy 4643was developed for welding the 6xxx series base alloys and developing highmechanical properties in the post weld heat-treated condition.This filler alloy was developedby 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 thatwill 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 weld7005 bicycle frames and will respond to heat treatment without dilution of the thin walledtubing used for this high performance application. Other heat treatable filler alloys havebeen developed including 2319, 4009, 4010, 4145, 206.0, A356.0, A357.0, C355.0 and 357.0 forthe welding of heat treatable wrought and cast aluminum alloys.

Work Hardening is used to produce strain-hardened tempers in none-heat treatable alumalloys. (Increases strength). This is influenced by mechanical energy leading to deformation.As the deformation occurs the alum alloy becomes stronger, harder and less ductile.

Precipitation 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.Thealloy is reheated to a lower temp and holding for a specific time. This heat treat producessuperior mechanical properties. Please note on the heat treatable alloys that haveundergone this treatment, the weld metal heat will change the mechanical properties in boththe HAZ and base metal.


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Aluminum Filler Metal Information:

AluminumFiller

InternationalSpecs

ChemistryMeltTemp

Yield Tensile

Electrode1050A

ISO / GermanyA199.5France A5Italy P-AP5

Electrode1100

ESAB OK18.01ConarcaoA400SPacweld 421AA

Al 99% -Mn0.05 Cu0.05 - 0.2Si - Fe0.95Zn 0.10

1190to1215F643 to657C

5 ksi34MPA

13 ksi90 MPa

Electrode1100 - H12

15 ksi16 ksi

Electrode1100 - H14

17 ksi 18 ksi

ER filler 1100 used to weld all 1XXX alloys plus 3003and 5005 alloys

Electrode1188

UNS A91188

Al 99.8%Si 0,06, Fe0.06Cu 0.005,Mn 0.01,

Zn 0.03.Ti0.01

1215F657C

Electrode2319

UNS A 92319used for Allithium aircraftalloy 2090

2319 is heattreatable goodstrengthductility on AlCu Casts

don't use 2319on 5XXX

Cu 5.8 - 6.8Si 0.2 /Fe0.3Mn0.2-0.4Mg 0.02Zn 0.1Ti 0.1 - 0.2

1010to1190F

543 to643C

2319 used on2219 2014 plusalum copper castalloys

Dont use on5XXX


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ER4XXX ALUMINUM ELECTRODES.

ER 4043 - 4047Moderate strength good corrosion resistance.(Lessstrength than 5356)

ER 4043 - 4047 Low sensitivity to cracking while weldingER 4043 - 4047 Lower weld ductility than 1XXX - 2XXX -

5XXXER 4043 - 4047 Can weld 1XXX - 3XXX - 6XXX 2014 / 2219 / 005 /5052 / 7005/7039 Al - Si and Al - Si - Mg casts

Electrode4043

Germany ISO

S - ALSi5Italy S-AlSi5France A- S5

"don't" use toweld high Mg5XXX 5083 -5086- 5456

ESAB 0K18.04Packweld425/AAThysen

UnAlSi5Century 331400Conarco A408

Si 4.5 - 6Fe 0.8, Cu0.3Mn 0.05Mg 0,05, Zn0.1Ti 0.2

1155F623 C

10 ksi69Mpa

Moderatestrength goodcorrosionresistance

Low sensitivityto cracks while

welding

Lower ductilitythan 1XXX2XXX5XXX

21 ksi145 Mpa

Can use on 1XXX

3XXX6XXX201422195005505270057039Al-SI + Al Si Mgcasts

Electrode4043 - 18

39 ksi270MPa

41 ksi285 MPa

On thin alumsheet 4047 isused as analternative to4043

Electrode4047

Germany ISOS- AlSi12Italy S-AlSi12France A-S12

Si 11 - 13Fe 0.8, Cu0.3Mn 0.15, Mg

1050F565C

Moderatestrength goodcorrosionresistance


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0.1Zn 0.2 Low sensitivity

to cracks whilewelding

Lower ductility

than 1XXX2XXX5XXX

Can use on 1XXX3XXX6XXX201422195005505270057039

Al-SI + Al Si Mgcasts. Fasterfeeeze than 4043can preventformation ofcrater cracks

Electrode4145

Si 9.3 - 10.7

Fe 0.8Cu 3.3 -4.7Mg/Mn/Cr0.15Zn 0.2

970F

Low sensitivityto weld crackson 2XXX

Good for

Al - CuAl -Si- Cucast alloysresponds to heattreat

can repalce 40434047 will result inlower ductility

ER 4145 Low sensitivity to weld cracking on 2XXX alloysER 4145 Good for Al - Cu Al Si Cu Cast Alloys. Respondsto heat treat. ER 4145 Can replace ER 4043 4047, willhowever have lower ductility.

Electrode4643

Si 3.6 - 4.6Fe 0.8, Cu1.1Mg 0.1 - 0.3Zn 0.1, Mn0.05Ti 0.15

1065to1175F573 to635C

4043 is agoodchoice for thewelding of heat-treatable alloysespecially the6XXX series. 4043has a lowermelting point and


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more fluidity thanthe 5XXX seriesfiller alloys. 4043has goodwelability. 4043wires are also less

sensitive to weldcracking with the6XXX series basealloys. 4043 issuitable forsustainedelevatedtemperatureservice, above150 deg F (65 degC).

KEEP THE ALUM CLEAN BEFORE WELDING.Aluminum has a great affinityfor hydrogen, which can be picked up from many sources, dirt, paint,moisture, markers, lubricants, etc. All mentioned can form hydrocarbonscausing serious porosity which can weaken the weld.

WELD POROSITY IS MORE OF A CONCERN WITH ALUMINUM THAN ITIS WITH STAINLESS OR STEEL. THE REASON STAINLESS ANDCARBON STEEL TYPICALLY HAVE MUCH GREATER YIELDSTRENGTH.

To clean aluminum, consider degreasing solvents and clean stainlesssteel brushes. Caution some grinding wheels will contaminatealuminum, (use wheels recommended for alum). Also on heat treatable

alloys, plasma gouging and cutting can cause micro cracks oncomponent edges, (remove edges with grinder).

ER5XXX ELECTRODES:

ER 5XXX Higher strength than other aluminumelectrodesER 5XXX used to weld 5XXX - 6XXX - 7005 alloysDon't use ER5XXX filler on 2XXX alloysER 5XXX Higher Mg Higher strength and crack sensitivitydecreases

ER 5XXX Pre heat and interpass max temp 150F 65C

Electrode5056

ISO/GermanyAlMg5France A-G5MCItaly P-AG5


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Electrode5083

ISO /GermanyAlMg4.5MnFrance A-G4,5MC

Electrode

5154

ISO AlMg3.5Germany

AlMg3France A-G3C

Electrode5183

Germany S-AlMg4.5MnFranceAlMg4.5Mn

Mg 4.3 - 5.2

Si/Fe 0.4Cu 0.1Mn 0.5 -1Cr 0.05 -0.25Zn 0.25Ti 0.15

1075to1180F579TO637 C

Dont use on hightempapplications5183 is forwelding highmagnesiumalloys to meethigher tensilestrengthrequirementsthan 5356.

Use on 5083 and5654 basematerials whenrequired tensilestrengths are>40,000 psi (276MPa) or greater.Typicalapplications arein the marine andcryogenicindustries, andhigh strength

structuralaluminumfabrication.


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REDUCE THE ALUMINUM "BLACK OXIDES"

The black soot that frequently occurs with MIG aluminum welds, is a

combination of aluminum and magnesium alloys that combine with oxygenand form oxides that appear black. The oxides that form have a lowerboiling point than the arc temperature, they evaporate and condense on theweld or HAZ area. Expect more soot from higher magnesium alloys. Forexample the common 5356 filler metal can provide more soot than E4043filler metal.

Excess soot is usually an indication of weld porosity issues. The soot cancaused and corrected by the following.

[A]INSUFFICIENT WELD ENERGY. TO ASSIST IN THE REMOVAL OF THE

ALUM SURFACE OXIDES.INCREASE WELD CURRENT / WIREFEED OR DECREASE WIRE SIZE FOR MORE CURRENTDENSITY.

[B]ARC LENGTH THAT IS TOO LONG.INSUFFICIENT PLASMA ARCENERGY 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 ALUMOXIDE SKIN IN FRONT OF THE WELD. BACK HAND (PULL) WILL PROVIDETHE 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 AFFECTEDZONE WIDTH. IF USING HELIUM ENSURE HELIUM FLOW METER IS USEDAND ENSURE HELIUM FLOW RATE IS A MINIMUM OF 45 CUFT/HR

[E]WELD SPEED TO FAST. MAY NOT ALLOW ADEQUATE BREAKUP ORREMOVAL OF ALUMINUM SURFACE OXIDES.

[F]ALUM SURFACE CONTAMINATED.NEEDS CLEANING.

[G] CYLINDER GAS CONTAMINATED, TYPICALLY DUE TO POORDISTRIBUTOR GAS FILLING PRACTICE WHICH LEAVES EITHER CO2,OXYGEN OR MOISTURE IN THE CYLINDERS.

Electrode5356

GermanyFrance S -AlMg5Italy S-ALMG5

ESAB OK18.15Pacweld 430A

Mg 4.5 - 5.5Cu 0.1Ti 0.06 - 0.2Cr/Mn 0.05-0.2Zn 0.1Si 0.25 / Fe0.4

1180F637C

Dont use on hightempapplications.5356 is a greatgeneral purposefiller alloydesigned for thewelding of 5XXX


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Conarco A404ThyssenUnAlMg5

series alloyswhen


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THIS ALUMINUM MIG WIRES A BARGAIN.

If you get your aluminum MIG wire at a bargain price, itslikely you will have weld consequences. To test analuminum MIG wire, take two 1/4 alum plates, six incheslong. Start a 3/16, horizontal fillet weld approx. one inch

from the end of the plate. Make the weld is four incheslong. Don't weave use fore hand. After the weld hascooled, put welded plate in vice and use hammer to foldthe plates in on the weld.

In contrast to steel welds, a good, alum weld with properside wall fusion should break in most cases in the weld

metal. Examine the broken weld surface for porosity. Clean looking, small pore porosity isfound in the best of aluminum welds. Blackish looking small porosity often results fromlubricants from the material surface. Small gray, oxidized weld porosity often results from airtrapped in the joint or oxygen from the gas cylinders or lines. Extensive shiny porosity maybe an indication of moisture pickup. Ensure synthetic impermeable hoses are used for youraluminum MIG gas delivery rather than neoprene or rubber hoses.

Weld porosity can be blamed on many materials that can contaminate both the weld wiresand base metals. With aluminum, hydrogen is the prime cause. The bottom line keep theplates clean and at the ambient shop temperature. If necessary for your application grind theweld edges. Provide a protective cover for the alum weld wires. When the weld wires are notin use store in clean dry area. Good manufacturers of aluminum MIG wires will use extensivemanufacturing controls to ensure you have a clean consistent MIG wire. There is a price to

be paid for this weld wire quality. Compare yourbargain priced aluminum wire with a quality andconsistent product from a company like Alcotec.

Aluminum, Oxidation, Hydrogen and Porosity.

Aluminum has a high maximum solubilityfor hydrogen atoms in the liquid form anda low solubility at the solidification point.


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Hydrogen dissolved in the liquid weld metal will try to rise out of the weldduring the aluminum solidification. Some hydrogen gas pores will betrapped and porosity will occur.

Aluminum 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 layeris porous and can easily trap moisture, oil, grease and other materials. The aluminum oxidelayer provides excellent corrosion resistance, but must be removed before welding as itprevents 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 allused to attack the oxide layer. When MIG welding if the layer is not removed sufficiently a blacksoot 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.

The majority of aluminum weld porosity results from entrapped hydrogengas 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 orcleaning 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 gascylinders. Water from the porous, hydrated, alum oxide layer on the base metal surface.

[d] 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 youcan always find porosity in the alum weld, the real question is how much is acceptableand what inspection and weld process control method will be used to control theporosity.

To reduce aluminum weld porosity potential, slow down the weld

solidification rate to allow the hydrogen to exit. Reduce alum weldporosity with the following 11 points.

[1] To remove the alum surface oxide consider a die grinder(>30,000-rpm) rotary, coarse carbide file. An effective cleaning solution is acetone, bewarehighly flammable..

[2] Increasing weld parameters, with MIG increase the wire feed rate.

[3] Increase weld size.


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[4] Avoid weaves.

[5] Slow down weld travel speed.

[6] Use smaller diameter MIG wires.

[7] Evaluate the weld procedure so that weld heat and weld sequence is used as a tool forporosity reduction.

[8] Use lowest possible MIG weld voltage. Low weld voltage results in short arc lengthswhich create more energy in the arc plasma providing improved arc cleaning action of thesurface alum oxides.

[9]Use a higher energy gas mix like 60 helium - 40 argon. The helium requires higher weldvoltage. The 60 helium mix is superior to the common 75 helium 25 argon mix, as the thehigher argon content helps stabilize the arc and provides superior weld cleaning action.

[10] Don't use MIG wire wipes clipped on the wire.

[11] Don't use anti spatter within 2 inches of the weld. If you know how to set a weld youwould not use anti-spatter.

mig welding aluminum tips

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