aluminum on 125 Handler

[galto]

I see on the Hobart Handler 125 that aluminum isn't a sugested material. I don't see why not if it has the MIG attachment. Can anyone let me know why trying to weld aluminum with the 125 is a bad idea?
Or atleast why it isn't listed on the sugested materials list?

I can do gas(brazing etc.), but figure I should try this wire feed method and see how it goes.

Thanks!

[hankj]

I see on the Hobart Handler 125 that aluminum isn't a sugested material. I don't see why not if it has the MIG attachment. Can anyone let me know why trying to weld aluminum with the 125 is a bad idea?
Or atleast why it isn't listed on the sugested materials list?

I can do gas(brazing etc.), but figure I should try this wire feed method and see how it goes.

Thanks!

The big problem is the rate that aluminum can dissipate heat. A 125-amp machine can weld thin aluminum sheet if it has a sufficent volt/amp curve to get into spray arc.

I have a 200-amp class machine, and it welds aluminum just fine, but it can supply arc voltage that is much higher than a 125-amp machine at any given feed speed. Therein lies the delimma!

Hank

[galto]

Would pre-heating the aluminum be OK?

I plan on doing very thin aluminum plates on some heat sinks and filling incomplete burnouts in castings.

I could get the parts up to the 300C or so range, I don't want to get much higher than that or they will plastically deform during handling.

As far as the volt/amp curve, what do you look for in an aluminum welder?

What are the conditions that must exist to create a spray arc?

Again, thanks for taking the time to answer my novice questions.

[hankj]

Spray transfer occurs in an argon-rich (for aluminum, you need 100% argon) atmosphere when the arc voltage is high enough to ionize the shielding gas. A good average is 22- volts, but there needs to be enough current available at 22-volts to generate enough heat for the weld! At 22-volts, my MM135 will only deliver 40 amps. When I get up into the 125-amp range, I'm only putting about 18-volts out, which is not enough for the process.

You may have decent luck with thin sheet, but I doubt, even with preheat, that you'll successfully weld on any significant sized casting.

There will be some more opinions coming along, I'm sure. Those are my 2¢!

Hank

[Airgasjim]

Well really there are two problems that exist with weldin with a 125. The first Hank explained (lack of power). The other one and almost as frustrating is trying to feed aluminum through a 10' liner. I typically explain it as trying to feed wet spaghetti through a drinking straw. Its not fun at all.