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The job site requires welding both aluminum and steel (each to themselves only) for different areas of the project. The contractor has a dual purpose wire feed welder (aluminum and steel) but I am unsure that a dual purpose welder will be optimal for both types of metals.

Can you get quality welds from a multiple metal wire feed welder, or do you need separate units for steel and aluminum?

I'm looking to understand any potential differences between the three types (aluminum, steel & dual) of welding machines and the welds they produce. Likewise, any testing results that indicate the strength of welds for both types of metal using both dedicated and dual purpose welding units would be useful.

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  • $\begingroup$ @JamesJenkins: you can always ask the contractor to justify the welder being proposed. If the contractor can't do that you then have reasons for concern. The contractor's response will also indicate the competence of the contractor in doing the job required. $\endgroup$ – Fred Feb 6 '15 at 13:11
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    $\begingroup$ @Fred the contractors response is going to be based primarily on the fact that he already owns the dual machine, and did not budget in his bid for purchasing two new separate machines. He is not going to go looking for or telling you about any sources that suggest he needs to go buy new machines. $\endgroup$ – James Jenkins Feb 6 '15 at 13:17
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The short answer: it's not optimal, but may work. Hopefully if these welds are critical, they're being performed to some code (In the US, for most structural work they'd be AWS D1.1 and D1.2 respectively.) Aluminum is considered among the hardest metals to weld well, so quality control is especially important there. Overall, the wire feeder itself doesn't have too much impact on weld quality - a bunch of other factors including the power source, welder (person), joint preparation, consumable choice, and cleanliness of the welding environment will make a bigger difference.

Steel is an easier metal to feed through a welding lead, because it has a higher column strength, and is less likely to buckle. It's guided by a narrow tube ('liner') that runs through the cable, and is typically just pushed by the wire feeder (which may be built into the power supply or a standalone unit.) Because aluminum has a lower column strength, it is more likely to buckle, and thus not feed well. When this happens, the wire will stop feeding out of the gun, and just fill up the liner which then gets jammed and has to be cleaned out. This is a pain for the fabricator, but shouldn't affect weld quality other than maybe causing some extra starts and stops.

For a short welding lead, and using large diameter aluminum wire, they may well be fine using the same wire feeder. If not, there are a number of other strategies. For small amounts of work, they may use a spool gun which is essentially a miniature wire feeder which the welder carries around. A small spool of aluminum wire is actually inside the gun, along with the drive rollers which only have to push the aluminum a few inches as a column before it gets to the weld. Another common strategy is a push-pull gun, where the wire feeder pushes the wire with to help it come off the spool, but additional drive rollers in the gun pull it to keep some tension on the wire as it goes through the liner. It is possible that they are using the same wire feeder, but changing from a conventional MIG gun to a push-pull gun when they switch from steel to aluminum. That would be a common practice.

At the end of the day, I wouldn't be worried about their choice of wire feeder. For the most part, it will work or it won't. I would be more concerned with their overall quality control system. Are welders working to a written procedure? Have welders been tested before they're set loose to weld? How and how often are finished welds inspected? If they are welding to a code, these answers will be dictated by it. If they are not welding to a code, you can get a rough idea of what level of QC they employ.

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This assumes US codes are used.

The question of whether or not a quality weld can be produced needs to be proven through testing. Per AWS (American Welding Society) codes (D1.1, D1.5, etc) the welder (person) must be certified for the weld type (FCAW, SMAW, etc), the materials to be joined, and the position to be welded (flat, vertical, overhead, etc).

In addition to all of that, the actual weld to be used needs to have been tested to prove that a quality weld can be made in a perfect situation. This is through the PQR (procedure qualification record) and WPS (weld process specification) process.

All welds are also tested. This can be visual all the way up to xray. At the very least all welds are supposed to be visually inspected.

All of this testing and paper work is there so that you have the best possible chance of getting a good final product. It is a lot of work and expense, but it is the only way that you can have confidence in a weld without wondering.

In answer to this specific question, if all of the testing and paperwork has been done correctly, the contractor's model of welding machine doesn't really matter.

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  • $\begingroup$ Just to be clear, there are many different codes that could apply depending on what you're welding. For example pressure vessels or pipelines aren't generally done to AWS codes in the US, but ASME or API respectively. Also depending on the provisions of the code, not all WPSs have to be qualified by testing (PQR.) Also, strictly speaking, AWS codes will require qualification, but not certification. Each of those things alone could be their own question, if anyone cares about the details. In most codes, the specific wire feeder will not be an essential variable. $\endgroup$ – Ethan48 Feb 6 '15 at 15:13
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A prime example of welders that would perform such welds would be a Lincoln PowerMig 210, Hobart Handler 210 MVP. This is just to name a few. Miller and Everlast also have the "MVP=Multi Variable Process" units. Keep in mind most Multiprocessing welders have a lower production time or more clearly defined as "Duty Cycle time" due to the Multi-variable process of using 120v or 240v. All of these units have a max thickness close to production grade but are more suitable for the DIY person. I personally use a Lincoln PowerMig 210. Not that it's any better but the all around characteristics of welding GMAW=MIG welding MIG also referred to as Metal Inert Gas, SMAW=Shielded Metal Arc Welding also referred to as Arc Welding, FCAW=Flux Core Arc Weld, FCAW-S=Shielded Gas Flux Core, GTAW=Gas Tungsten Arc Welding also referred to as TIG in both AC and DC electrode negative or positive, And Aluminum Spool gun Mig welding. These are very versatile machines capable of handling most DIY jobs with a high quality of weld deposition. The welding process of FCAW-S has the highest deposition rate and is used more commonly in high production areas. Downside of these units would be on average 3/8" max carbon steel or 1/4" Aluminum thickness.

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Yes,you can get good quality welds of both steel and aluminum with the same welding machine. A wire welder or MIG gun {Metal Inert Gas} is normally loaded with a 30lb. reel of copper coated steel wire of various diameters{20-45 mm.} depending on the thickness of steel to be joined.To weld aluminum you will bypass the steel reel drive ,plug in an aluminum spool gun loaded with a 5lb. reel of aluminum wire,here again of varying diameters,and change the weld cover gas from the CO 2 mix to a straight argon cover gas.Years ago the standard wire welding machine would have also had to have an additional component attached, a high frequency rectifier,but todays wire welders commonly come factory ready to accept an aluminum spool gun.The operators experience and dexterity now comes into the picture,but a failed weld will not be the machines' fault.

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    $\begingroup$ MIG wire is commonly in the .020"-.045" range, not 20-45 mm. It is available in larger sizes too, but none that approach 20mm. $\endgroup$ – Ethan48 Feb 8 '15 at 17:34
  • $\begingroup$ 20-45mm is roughly almost 1-2 inches (25.4-50.8mm) $\endgroup$ – Chuck Oct 19 '15 at 0:27

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