[bolt_boy_49]

I practiced mig welding aluminum today. I had a lot of trouble getting a good start to my weld. Once I got going I had what appeard to be a good weld. Can anyone offer a suggestion as to why Im not getting a good start?

Im using a millermatic 210 with a spool gun.
The aluminum is 1/2"

[NEW INTERIORS]

The key to welding Alum,Is to make sure it is super clean...

[bolt_boy_49]

What is the best way to make sure its clean? I have a wire brush for aluminum only. what else should i do?

[ericnova72]

Pre-heat the material. Your problem is that it takes several inches of weld before there is enough heat in the base metal for things to go smoothly. This is the same reason that TIG is the preferred method on aluminum, you use the TIG torch to heat the aluminum at the start of the weld before adding filler rod.

[OneMoreTime]

Some tips on welding aluminum:

http://www.lincolnelectric.com/knowl...ntent/alum.asp

There are aluminum flux materials that help with cleaning the metal as well..use a run on run off tab to help with the starts..

Sam

[bolt_boy_49]

Wow Thank you all for the quick help.

[NEW INTERIORS]

I use a very fine sanding pad,And lightly hit it,When the machine is set right and the alum is clean right,You shouldn't have to pre heat it.You should only have to pre heat it if your machine isn't big enough.Don't be scared to run it a little hot.

I like to use these sanding disc.(But make sure it's a fine one)..

[cboy]

Do any of you get away with using the 75/25 gas mix on aluminum...or do you have to switch bottles and use a gas just for alum.

I'd like to practice on alum...but don't want to invest in another bottle and a special gas mix just to plunk around. (I have the alum wire...just not the gas).

[oldred]

You can't use 75/25 sorry to say, it sure would make things simpler (and cheaper) if the mix was that versatile but unfortunately it's not.

From the looks of the welds in that pic a tad more heat would probably help and some pre-heat would help also, especially on heavier stock. The reason the weld does not start out very good is, as ericnova pointed out, the material is sinking off the heat too fast and as it becomes hotter from the weld the bead will smooth out, pre-heating would solve this but just welding a little hotter would make a big difference too. Clean throughly with a stainless steel brush and make SURE the brush has never been used for anything else. A common mistake is to grab up a brush that has been used for various other chores thinking because it is stainless it will be fine but if it is contaminated it could easily cause problems, don't use your Aluminum cleaning brush on carbon steel (especially important when TIG welding and critical when using Oxy/Acetylene). Those sanding discs New Interiors mentioned are also an excellent way to clean Aluminum and are my first choice unless a brush is the only thing practical to reach into the joint.

[bolt_boy_49]

Could you use 100% Argon for steel? That would still get cboy down to one bottle.

[oldred]

Nope that don't work very either, not with MIG anyway.

[timothale]

My old neighbor in Calif used to build circle track cars and I always had him do my critical welds. He said some of the made in China sandpaper will contaminiate the metal because of the adhesive they use. He always cleaned the parts with acetone as the last step.

[NEW INTERIORS]

Originally Posted by timothale

My old neighbor in Calif used to build circle track cars and I always had him do my critical welds. He said some of the made in China sandpaper will contaminiate the metal because of the adhesive they use. He always cleaned the parts with acetone as the last step.

Never had a problem using the pad's,And never had to use Acetone,And never had to pre heat any of the Alum I did, I did ''ALL'' the Alum work,For one of the biggest (if not the biggest,,I think he is)offshore boat company in the world for about 10 years before I became disabled. He also own's a bunch of shipyard's that only build's his boat's. 300 foot supply boat's and Ice breaker's..