Hello, metalworkers!

Haven't been by in a while. Been busy getting ready for a six month volunteer
stint.

We know by sooting aluminum and torching it the soot will burn to indicate the
annealed condition has been reached. I doubt this is more than a coincidence as
I read the aluminum oxide layer become mobilized and can be removed by rub
soldering at some temperature, so I speculate annealing happens to happen at
near the same temperature. That is, buring off the soot doesn't anneal the
aluminum, it's the heat that anneals the work.

Is this an effective method of preparing aluminum for soldering? Does the soot
act as a powerful reducing agent, turning the Al2O3 into reduced Al at the
surface?
Can presooting aluminum, torching it to remove the soot, and applying flux with
the tip of a solder wire, then rubbing with solder wire be a way of tinning
aluminum for soldering?

Inquiring minds want to know. So do I.

I have the equipment, solder, and flux, but not a single scrap of aluminum
other than a beverage can.

I'll be working with 0.080 inch thick aluminum soon.


Yours,

Doug Goncz ( ftp://users.aol.com/DGoncz/ )
Student member SAE for one year.
Loves in my life:
Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically.
So that is who I spend my time with.

Doug Goncz wrote:
Hello, metalworkers!

Hi Doug!
(Snip)

Can presooting aluminum, torching it to remove the soot, and applying flux with
the tip of a solder wire, then rubbing with solder wire be a way of tinning
aluminum for soldering?

The way that I misunderstand the process is as follows:

* Use an uncontaminated (by other than aluminum) stainless steel brush to knock
off the thickest part of the surface oxide of both pieces to be joined.

* Clamp the pieces in place and cover them as much as possible with a
thermal isolating blanket. (Kaowool)

* Heat the bejeezus out of the pieces until tin solder flows.

* As you add to the puddle, use the stainless brush in your third hand to scratch
the aluminum oxide off the surface under the puddle.

* Keep scratching for the entire length of the joint. The solder will act to isolate
the new surface from oxygen. New oxides will not form.

* Let the workpiece cool. Be careful that the pieces not move during the critical
liquid - plastic - solid phases.

I have never used this process but it seems reasonable. A bright fella such as
yourself will probably want to build an argon chamber to further limit oxide formation.

Let us know how it goes OK?

--Winston

Thanks, Winston, Leon, and Gary!


Yours,

Doug Goncz ( ftp://users.aol.com/DGoncz/ )
Student member SAE for one year.
Loves in my life:
Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically.
So that is who I spend my time with.