DC welding of aluminum

By microfusionweld Date 09-07-2007 16:29

My AC capability on my Lincoln recently stopped working. I had an aluminum fixture that I had to send to another shop. I spoke to them after I received the part. They told me they welded it using DC. How is that possible. I enclosed some pics of part.

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By Lawrence (*****)

Date 09-07-2007 16:46

The short answer is that they welded those massive aluminum joints with DCEN and Helium shield gas.

There is some technique involved, and surface prep becomes even more important and regimented. (others here have more experience so I'll leave it to them)

But it is a pretty common process in the Aerospace world for joining thick sections of aluminum.

By reddoggoose (**)

Date 09-07-2007 17:52

It is possible, but like Lawrence mentioned it is typically done on thicker material and surface prep is very important. Since there is no AC cleaning action all oxide need to be removed. Welding aluminum on DC- is a bit tricky at first, but once you get a feel for it, it isn't too bad. The biggest problem in my experience was just knowing when the puddle was ready to start adding filler. Since there is no AC, the puddle doesn't give the nice shiny appearance to let you know when to start adding filler. After having the puddle fall out on me a few times I started to get the hang of it. When I had to test to qualify for my certs, we used an argon/helium blend in a gas mixer. It's been too long now and I don't remember the mix percentage.

By 803056

Date 09-07-2007 20:57

Use an EWTh-2 tungsten electrode with a tapered end preparation. Tapered, not ground to a long needle like point. You will want to use as large a tungsten as your machine will handle. Set up using DCEN. Use helium shielding gas. With helium, your flow rate will be three to four times that of argon.

Cleaning is VERY important. Look at "Tricks of the Trade" for a thread by rebeka on cleaning aluminum. There are sufficient details there to get started. Clean and weld within a four hour window, or clean again.

Best regards - Al