Newbie with a problem TIG welding Aluminum

[JonnyTIG]

jrscgsr,
the tempurature for annealing aluminum is quite a bit hotter than the temp for burning off the black smut from an acetylene flame. Anyhow, the base metal would have to be held at the elevated temp for a few hours to get to a completey soft fully annealed state. The amount of annealing that occurs during the pre heating that I mentioned is minimal, and depending on the alloy, (naturally aging vs stablized) the part if previously hardend would react when cool and begin to return to it's hardened state over a matter of time. Being that the parts are dissimilar alloys, one being what looks like a disk of 6061 and the other being what looks to be a casting (probably 356) it would be benificial to at least partially anneal the wrought or extruded disk as to promote a more equal shrinkage and deter possible cracking in the weld zone.

[SundownIII]

BigL350,

You're probably melting your tungsten (1/8" if I remember correctly) because you have your balance set incorrectly. Too much electrode positive (cleaning side of the AC cycle) puts more heat into the tungsten and less into the workpiece.

Never seen a tig welder with an "auto" balance control.

I suspect you've got a 185A Lincoln, transformer based machine. As I said previously, thoriated is not the proper tungsten for AC welding on a transformer. The tungsten will splinter and form small ***** which drop into the weld bead.

With the "mass" of that workpiece, you're going to have a hard time getting a good bead, even with preheat. An argon/helium blend may give you a better shot of making it happen. I've got a Dynasty 200 but I'd be firing up the Sync 250 for that job. You've got to keep your arc focused on the base casting til you get your puddle. Then add filler (not before) and wash the molten metal up to the 1/4" plate. You will never get a decent weld melting the filler with the arc.

Even with a clean surface (which your's is not even close) cast aluminum will emit junk from the base metal. That's why I said you may need to butter it up. (means laying down a bead, grinding it out, repeat til you get clean base material).

That's a difficult weld to make with an underpowered machine. For an inexperienced tigger, it may be dang near impossible.

[jontheturboguy]

A couple of things:
You didn't turn the machine to AC.
Your machine doesn't have enough tuna for that shark.
You didn't clean the aluminum well enough.
You sand blasted one or both of the parts.
Your tungsten is too small and melting away.
Poor gas flow.

Check those, and let is know.

[SundownIII]

Brilliant, just freaking brilliant.

[6010]

Your problem will lie somewhere within the things Jon gave you to look at. But even if you had cleaned this to perfection and had good argon flow, looking at what you are welding it is like Jon said ... 100 amps is not enough tuna for the shark.

[jontheturboguy]

Brilliant, just freaking brilliant.

Hard to see every ones replies here in the mobile phone. Looks like i gave cliff notes for every thing you posted. :-)

[jrscgsr]

jrscgsr,
the tempurature for annealing aluminum is quite a bit hotter than the temp for burning off the black smut from an acetylene flame. Anyhow, the base metal would have to be held at the elevated temp for a few hours to get to a completey soft fully annealed state. The amount of annealing that occurs during the pre heating that I mentioned is minimal, and depending on the alloy, (naturally aging vs stablized) the part if previously hardend would react when cool and begin to return to it's hardened state over a matter of time. Being that the parts are dissimilar alloys, one being what looks like a disk of 6061 and the other being what looks to be a casting (probably 356) it would be benificial to at least partially anneal the wrought or extruded disk as to promote a more equal shrinkage and deter possible cracking in the weld zone.

Depending on the part he is welding it may not be a good idea to partially anneal the part if it is put under stress. Aluminum anneals between 300-400 c and must be held at these temps for .5-3 hours depending on the alloy and whether it is wrought or cast aluminum. This is to fully anneal the part. Just saying consider the forces the part is going to see. The part my begin age hardening after burning off the soot, but it will be softened. Try "painting" a piece of 6061 t6 sheet with acetylene soot and than burn it off. The aluminum is very soft after, easily formable by hand. Not something you'd want in a critical part.

[6010]

Sorry Sundown. Somehow I missed you longer post - I guess it was kinda late posting for an old man like me. I do have a question for you. I have never tried the mig welding with a spool gun, something I plan to do soon since I just bought some AL wire, and recently acquired a spool gun. My question is when you are stretching the capabilities of your welders as far as amps go ( say you have a 200 amp tig and a 200 amp mig ) does one have a better chance of giving you a satisfactory weld ?? My gut feeling is the tig would have an edge since you would have more control over the heat imput due to the fact you could keep the heat in one place a long as you needed. This is assuming all other things are equal - gas flow, pre heat, etc.

I have seen some pretty mig welds on Al boats but don't know it they are any stronger than a weld with a tig unit would have been. I know you have had a lot of experience welding Al so I thought I would someone who has used tig and mig for repairs. I have done a little reading on each process but haven't run across anything that compares to two process as far as strength. I do know the mig would be much faster but don't know if it has any other advantages.

[Broccoli1]

A proper weld in each process will have the same Strength.

[Broccoli1]

In general you are limited to about 16g with MIG and AL so MIG is not ideal for thin sheet work.

In general TIG is limited in the heavier stock.

This is based on the average Machines.

BUT add Pulse to the Migoline and Inverter technology to the Tigger and things change

http://www.millerwelds.com/resources...loys-GMAW-GTAW

http://www.millerwelds.com/resources...W-Fabrication/

http://www.millerwelds.com/resources...e-on-Aluminum/

[Broccoli1]

http://www.alcotec.com/us/en/educati...e/qa/index.cfm

Just a couple links I have saved in my Bookmarks

[SundownIII]

6010,

Not sure I fully understand your question or that I could provide a "brief" answer to what I think it is. This is a very complex issue and some of the threads Broc posted may shed more light on the subject.

With that said, I'll post a couple of my comments.

It's never a smart/good thing to try to exceed the capabilities of the welding machine you're using. As mentioned, a tig or a mig weld will have comparable strength if executed properly. Tig gives you a few more options which I will discuss later.

The reason you see, say an aluminum boat mig welded is because of "speed". A company I work with quite closely just completed a 45' aluminum oyster dredge boat. 95% of the welds on that boat were done using mig. Had tig been used, that boat would still be in the shop and 10% finished. Using today's technology (pulsed mig, push pull, etc) an experienced mig welder can come close to tig weld appearance and do it much, much faster.

Mig, being a DC process, puts a higher percentage of "heat" into the weld, but you're limited here to the machine output. Only option with mig is to go to multi-pass, which, because of the speed factor, is a viable option.

Tig, and here we're talking AC welding, uses a portion of the AC cycle (depending on the balance set) to accomplish the cleaning effect. Staying in one spot does not always mean greater penetration, but rather, simply adding heat to the base metal (not what you want). With today's inverter technology, a welder is able to focus the arc (higher freq) to obtain better penetration. Still comes down to the available amps though. Going to an Argon/Helium gas blend can further increase the heat in the arc column. Generally, the higher the Helium content, the higher the heat, but high Helium mixes also increase the difficulty in starting an arc.

For really thick, high mass, material, most experienced tiggers will go DC tig and use a pure Helium covering gas. This will give you the most penetration of all the tig processes. DC tig is not an easy process to "master" and many will get frustrated and "give up" before they achieve success.

Then you've got guys like Fusion King with their Dynasty 700's whose "capabilities" generally far exceed the type of work they normally encounter. Just because you've got the capability to tig weld at 500+ amps doesn't mean that it's easy. It takes effort and practice to get used to working with that kind of "heat". It's definitely not something I would want to do on a regular basis.

In summation, there is no easy, cut and dried solution that fits every situation. For the "average guy" he needs to be aware of what his options are. Those include preheating, gas blending, and machine setup. In this regard, tig gives you more options, but tig can never compete with the speed of a properly setup mig.

[welder_one]

sundown, so what your sayin is?????


jokin... wel said

[yorkiepap]

Hey BigL350,
The guys have provided solid information regarding aluminum & the inherent issue that can/will arise. Aluminum is quite finicky & cleanliness is next to godliness with aluminum. You may think it's clean & then you see similar issues as you have experienced. You want to keep all your steel & aluminum tools kinda segregated so as not to contaminate your alum. by using grinding wheels/discs or brushes that have been used on steel. Bear in mind..... aluminum needs to run HOT & in the case of MIG..... HOT & FAST.

To 6010: You have gotten superb information from SundownIII regarding TIG & MIG & the associated parameters each will be fruitful. Since I do both aesthetic items, classic/show car accessories, & production items, I use both processes. TIG is a necessity for the "looks" of the auto parts, & MIG is the necessity for the production items. The price is quite different as the TIG items cost twice or more the cost of production items. The production items have to be done fast, so MIG fills the bill & allows a handsome profit margin. As stated, when done properly, strength is equal with both processes. I have (2) spoolguns, shop & mobile. They have been great with multiple applications such as the road jobs getting to do flux-core, 70S-6, & 4043/5356 on one outing..... really makes for nice $$$. Do as much practice as possible to really get the "feel" of using a spoolgun.... you will find it indispensable & wonder why you waited so long to get one.

Denny

[Goodhand]

6010,
With that said, I'll post a couple of my comments.

Excellent! I've just added your explanation to my welding folder in case a friend should need the info. Of course I'll give you credit when I pass it on.