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Old 02-04-2019, 08:40 AM
cliffrod cliffrod is offline
MetalShaper of the Month January 2020, March 2022
 
Join Date: Dec 2014
Location: Spartanburg, SC
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I like gas welding- that doesn't mean I'm great at it. Maybe this will help.

You didn't mention what glasses or lens you are using. Kent's TM2000 lens is not cheap, but it is indispensable to be able to see the puddle. All color gradient is eliminated. It will simply show white for heat and the puddle as glossy or shiny when it melts/forms. Welding thin aluminum is such a razors edge type of balancing act that you need whatever advantage you can get. That lens is one of those advantages. I use mine when gas welding steel as well. It's money very well spent.

For aluminum, you need to flux all parts that are tangent to the puddle, not just the rod.

Air is an insulator, not a conductor. I love the story about the camper who slept on the ground one night and woke up half frozen the next morning. He realized he had been trying to heat the entire earth with his body.... Welding is the same thing- that steel table will suck the heat out of your welding project in the same way. Get some air or brick between the part and the table.

If you melt the rod into the joint (not cool, wrong method, unprofessional, poor weld, etc, etc) and then try to heat the lumpy mess into a smooth puddle, it will overheat and either fall through or boil/bubble/effervess and make a bad porous weld. Fail, fail, fail. Don't do it. It is the wrong way to braze, too.

The filler rod needs to be very close to the flame and the puddle so it is almost as hot as the base metal in order to liquify instantly as you dip it into the weld puddle. This simultaneously cools the puddle so it doesn't drop through and fills the puddle so the weld seam is not undercut. The temperature of the puddle is manipulated by the flame of the torch, rate of progress and the dipping of the filler rod.

Welding thin aluminum requires establishing your puddle and moving forward very quickly- if not very, very quickly- using the filler rod to keep the temp of the puddle just melted enough to push forward. For a short bead, it will be over before you know it. It's nothing like crawling along welding steel. Don't know the actual numbers , but it's probably at least 4x or 5x faster in aluminum than steel. You're really moving. Practice, practice, practice.

Hang around and an expert or few may add to the thread.
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Last edited by cliffrod; 02-04-2019 at 08:41 AM. Reason: Typo
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