10 Questions You Should to Know about Aluminum Mig Welding Wire

By ssbn727 Date 10-16- 21:16 I think Lawrence is on to something with his comments...

On another not, I found this article while reading some of the articles in the archive for the Fabricator:

http://www.thefabricator.com/article/aluminumwelding/succeed-at-welding-thick-aluminum-with-the-right-material-preparation-filler-choice-and-equipment

And as I was reading this, a couple of things jumped out at me regarding your situation...

Question: What are some equipment considerations?

Hoes: Water-cooled GTAW [gas tungsten arc welding] torches and GMAW [gas metal arc welding] guns should be considered for production welding of aluminum when amperage exceeds 150. Lighter air-cooled GTAW torches, GMAW spool guns, and push-pull systems sometimes will work for intermittent welding in this range, but will overheat when working at the higher amperage and duty cycles needed for production work.

Question: How do you prepare base materials and filler materials?

Burns: Materials need to be free of oil, grease, and moisture. Edges need to be more rounded than on thin materials to prevent premature melting, which causes lack of fusion (LOF) and lack of penetration (LOP). Often extended lands are used to get good fusion at the root, and the groove may be formed into a U shape.

Filler metals typically are from 3⁄32 (it should be 3/64" or at least 1/16th" diameter) to 3⁄16 in. These require special equipment and handling because of the springiness of the wire. When using large-diameter wire, note the duty cycle and be aware that most welding equipment such as torches and power supplies are rated using CO2, not argon or argon/helium mixes, which increase the heat to the gun and lower the duty cycle.

My question is:"If you are working from a WPS, is the filler metal dia. an essential variable in let's say AWS D1.2?" if not, then why not change to a thicker diameter and a more robust GMAW gun along with using an argon/helium mix (Is this a nonessential variable too?) so you don't need to increase the current and you control your HAZ better as well as the weld cooling down slower? i ask this because currently I'm not familiar with AWS D1.2.

Hoes: Oxide removal is also critical. As aluminum is stored, the oxide layer thickens, absorbs hydrogen, and traps impurities that can be absorbed into the weld puddle. Hydrogen, readily absorbed into liquid aluminum weld metal, turns to porosity when the weld solidifies.

Remove oxide with a clean stainless steel brush. Be careful not to use too much pressure if using a power tool. A power brush can dig into the aluminum, roll it over, and burnish it, trapping contaminants under the surface. Use grinding wheels and sanding discs that are designed for aluminum to minimize contamination. Machining instead of grinding can result in a cleaner surface, but remove all coolants or lubricants before welding. Paint and coatings also need to be removed from the weld area. Before brushing, clean and degrease with acetone, nonchlorinated brake cleaners, or citrus degreasers to avoid spreading contaminants. There are stronger cleaning solvents on the market, but exercise caution to use them safely.

Aluminum welding consumables should be properly stored to avoid shop dirt contamination and excessive oxide formation. This is especially important with GMAW consumables because the insulating oxide layer can cause problems with electrical contact between the aluminum electrode and the copper contact tip. Also, a large amount of surface area on small-diameter wires forces more contaminants into the weld deposit. GTAW cut-to-length consumables can be cleaned, but it is impossible with GMAW wire.

Question: What causes cracking? What prevents it?

Burns: Two things cause hot, or solidification, cracking. The first is stress-related. When the filler material solidifies at a temperature equal to or below that of the base material, stress caused by the metal shrinkage pulls on the molten pool or weld metal and causes cracking. The second is more of a chemistry issue. Alloys such as the 6XXX series that have a wide liquidus/solidus temperature range are more prone to cracking. The temperature difference creates a mushy range during solidification, forming coherent interlocking dendrites that result in voids between the grains. As the coherence range widens, it becomes more prone to what might resemble microcracking in the weld.

Stress corrosion cracking (SCC) is basically a chemistry issue in which some alloy elements, often accelerated by heat, have a galvanic reaction to each other. This is called metallurgical susceptibility. Environmental atmosphere and temperature contribute to this reaction that can lead to failure when stress is added.

Hoes: When the amperage is turned off quickly at the end of a weld, the puddle solidifies quickly and leaves a concave crater that pulls apart and cracks when it shrinks. Some advanced GMAW machines have crater-fill features with which the machine continues to weld at a reduced current for a period of time after releasing the trigger. This fills the crater and ends the weld with a convex bead, which is not prone to cracking. When using equipment without a crater-fill feature, double-back at the end of the weld to leave the crater on the weld. With manual GTAW, backing off the current with the foot pedal and adding a little extra filler metal at the end of the weld can also fill the crater.

TIG welds often have a tendency to crack if there is not enough filler metal, especially when working with crack-sensitive alloys like the 6XXX series. Dilute enough filler metal into the puddle to change the weld chemistry. Starving the puddle by not adding enough filler metal often leads to cracks. 6XXX alloys never should be autogenously welded (without filler). The silicon-alloyed 4XXX filler metal is less crack-sensitive than the commonly used 5XXX alloys but should not be used on alloys that contain more than 21⁄2 percent magnesium. The commonly used alloy is one of the only ones in the magnesium-alloyed family that can be welded with the 4XXX filler metals.

Question: What visible signs indicate a good weld? A bad weld?

Burns: Sometimes a good-looking weld is not a good weld. Unfortunately, the best way to evaluate a weld is to cut it apart, look at the depth of penetration, fusion, and porosity level. While we can’t use this method without destroying every weld, using known welding codes, such as those published by CWB and AWS, and following qualifying procedures increase the probability of achieving quality results.

Hoes: Look at bead shape. A good weld will be flat to slightly convex, without concave shapes or hollows between the ripples or in the crater, and have good wash-in at the toes. Check carefully for cracks using dye-penetrant inspection. If welds are ropey or convex, it is usually an indication that not enough energy was provided to the weld and cold procedures or undersized equipment was used. This is often an indication of possible LOF (Lack Of Fusion).

Question: How can a welder minimize the heat-affected zone (HAZ)?

Burns: Larger wire, fast travel speeds, and fewer passes all reduce the HAZ.
Hoes: High currents and helium additions to the shielding gas add energy when welding to increase travel speed, which reduces the HAZ. Use stringers, no weaving.

Question: How does shielding gas affect the thick weld?

Burns: In thick aluminum welding, helium is often added to argon to increase heat input. This can flatten the weld bead, increase root width penetration, and reduce porosity.

Hoes: Helium/argon gas mixtures, often utilized when GTAW on material over 1⁄4 in. thick and GMAW on material over 1⁄2 in. thick, transfers more heat to the weld than argon, which aids in welding thicker sections of aluminum. The broader bead profile resulting from the helium addition is not as deep in the middle, but it solidifies slower and allows some of the hydrogen to escape, reducing porosity.

Be sure there are no drafts or breezes removing gas from the weld area, leaks in the system, loose fittings, or spatter buildup in the nozzle. Check the purity of the gas. Contaminated gas really shows up with aluminum welding. Low-pressure tanks, below 500 lbs., can cause problems. Change them.

Question: How can a welder avoid wire feed problems?

Burns: Welding thick material with large-diameter wire can cause overheating of the contact tip if the weld gun or torch is not sufficiently cooled. The result could be loss of contact to the wire as well as excessive buildup at the exit of the contact tip. Use the proper equipment.

Hoes: Larger wire is going to feed easier than smaller wire when pushing. Use aluminum contact tips that are slightly oversized to accommodate the expansion of the aluminum wire as it heats up. Be sure the guide tube is plastic and the U-groove drive rolls are polished to prevent wire damage. The brake should be loose enough for the roll to spin freely without dumping wire when welding stops. Drive roll tension should be set back compared to what is used for steel.

Question: What extra steps should be taken to provide a safe environment?

Burns: Recognize that current must increase substantially to perform thick welds. With this increase in amperage, the heat and light given off as byproducts can result in burns from both temperature and ultraviolet light. Sufficient protection should be in place for both.

Hoes: Extra precautions should be taken to protect your eyes and skin and surrounding personnel. ANSI-approved safety glasses with side shields should be worn by surrounding personnel and as secondary protection from UV light under your hood. Higher levels of ozone result from thick aluminum welding conditions and enter your breathing zone. Adequate ventilation should be used to keep fume levels in conformance with OSHA standards while using caution not to exhaust shielding gas from the weld. Reference ANSI Z49.1.

The entire article really jumped out at me because it was fundamentally sound and logical... The basics... So take it and see if anything jumps out at you jsdwelder.

Here's the link:

http://www.thefabricator.com/article/aluminumwelding/succeed-at-welding-thick-aluminum-with-the-right-material-preparation-filler-choice-and-equipment

Here's another good article that can be used also to help your situation:

Aluminum welding Q&A: About soot, porosity, and equipment:

http://www.thefabricator.com/article/aluminumwelding/aluminum-welding-qa-about-soot-porosity-and-equipment

This one jumped out at me:

Q: My company fabricates a variety of aluminum products, and sometimes we find porosity in the welds after cutting and etching. We have checked our argon gas shielding carefully and find it adequate. We have also consulted the aluminum material suppliers, both raw plate and sheet and filler wire. They all have recommended cleaning processes, which we now employ. However, we continue to find porosity in our welds periodically. Is it possible the GMAW power source is influencing this contamination?

A: Unless the arc your present welding equipment generates is extremely erratic, you probably do not have a machine problem. Electricity generated in the arc is not contaminated. However, there is a type of pulse GMAW transfer available in some new generations of GMAW machines that can help eliminate this problem. This process superimposes a low-frequency pulse in combination with the normal high-speed pulse frequency. Certain low frequencies actually agitate the molten weld puddle at a rate that allows typically trapped gases or impurities to escape.

This low-frequency process offers several additional advantages. Low-frequency weld puddle agitation has been found to reduce grain growth in aluminum materials, which minimizes weld cracking susceptibility. The most obvious benefit is the weld surface appearance. The lower frequency provides a weld bead that looks very similar to GTAW welding but at the speed of the GMAW process.

Check with power source manufacturers to find out which offer this process. Ask suppliers for data to confirm a reduction or elimination of porosity and reduction of crack susceptibility. Also request a demonstration to see if the machine provides the GTAW-like bead appearance.

An oldie but a goodie: How to recognize, minimize weld smut:

http://www.thefabricator.com/article/aluminumwelding/how-to-recognize-minimize-weld-smut

Here's another one:

Tackling aluminum GMAW - Technology advancements in power sources simplify aluminum welding:

http://www.thefabricator.com/article/aluminumwelding/tackling-aluminum-gmaw

And this one which can be important in your case:  Age before welding in T6:

Frank Armao discusses why weld strength increases when incorporating an aging cycle prior to welding in the T6 temper...

http://www.thefabricator.com/article/aluminumwelding/age-before-welding-in-t6

Which filler wire is best for welding -T6 aluminum, or ?:

http://www.thefabricator.com/article/aluminumwelding/which-filler-wire-is-best-for-welding--t6-aluminum--or-r

And this: Achieving T6 designation for :

http://www.thefabricator.com/article/aluminumwelding/achieving-t6-designation-for-

Let's not forget this either: Preparing, testing bend samples:

http://www.thefabricator.com/author/frank-armao?page=2

Here's a little reference article covering aluminium H and T temper designations:

http://www.thefabricator.com/article/aluminumwelding/welding-aluminum

Now, if all of these factors have been covered and you still have issues then I wish you good luck in solving your problem.

Respectfully,
Henry

MIG welding aluminum Q&A

Spool guns improve the "feedability" of aluminum wire by locating a small, 1-lb. (

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4-inch diameter) spool of wire on a pistol-grip style gun. Because spool guns only need to feed the wire just a few inches before it hits the weld puddle, they eliminate the potential problems created by pushing soft aluminum wire 10 or 15 feet through a regular gun. By using a spool gun, you'll spend less time dealing with a "bird nest" of wire tangled around your drive rolls.

Here are some common questions and answers around the best equipment and filler metals for welding aluminum.

How do I know which spool gun to use with my welder?

First, understand what spool guns are compatible with your welder or the welder you are purchasing. Spool guns are sized to match the performance of the welders they are aligned with (refer to Fig 1). If there are multiple spool guns available, purchase one with the rating and duty cycle that best matches your usage requirements.

As a rule of thumb, higher duty cycle guns are designed for heavier usage, therefore causing the price to increase.

Fig. 1 - Spool Gun/Millermatic® Welder Selection Guide

Spool Gun Choice

Aluminum Wire Diameter

Duty Cycle

Matching Welders

Spoolmate 100

.030 or .035 in.

135 amps @ 30%

Millermatic 142

Millermatic 211

Multimatic 215

Multimatic 220 AC/DC

Multimatic 235

Spoolmate 150

.030 or .035 in. 150 amps @ 60%

Millermatic 142

Millermatic 211

Multimatic 215

Multimatic 220 AC/DC

Multimatic 235

Spoolmate 200

.030 or .035 in.

160 amps @ 60%

Multimatic 235

Multimatic 252

If you want to learn more, please visit our website Aluminum Mig Welding Wire.

Millermatic 255

Multimatic 255

Millermatic 355

Spoolmatic 15A, 30A  (15 or 30 ft. cables)

.030, .035, .047 or .062 (1/16th)

200 amps @ 100%

Multimatic 235

Multimatic 252

Millermatic 255

Multimatic 255

Millermatic 355

Which are the best Millermatic welders for welding aluminum in DIY, farm/ranch, general maintenance and other “occasional” welding applications?

We recommend purchasing a welder capable of welding on 230V input power due to the properties of aluminum. A lot of energy is needed to overcome aluminum’s thermal conductivity rate and melt through the aluminum oxide, which forms on the outside of bare aluminum. In general, 115V welders do not have enough power to overcome these properties and lead to poor fusion while welding.

Therefore, the Millermatics we recommend are the 142, 211, 252, and 255. Pick the machine that meets your needs in regards to welding output, duty cycle, physical size and feature sets. The most popular choice is the Millermatic 211 because of its Auto-Set feature, MVP plug, small size and high output. If it is a larger machine you are looking for, both the Millermatic 252 and 255 are great choices.

Which wire diameter should I use when MIG welding aluminum?

Fig. 2 - Typical Parameters for and Aluminum Wire

Wire Diameter

Amp Range

Wire Speed IPM

.030

100 - 150

500 - 600

.035

85 - 190

480 - 740

.047

125 - 240

360 - 470

.062

190 - 340

265 - 420

For more Submerged Arc Welding Wireinformation, please contact us. We will provide professional answers.

Are there any special storage considerations for aluminum wire?