Aluminum or Magnesium?

[Xray]

Hi all! This is my first post on the Miller forum.

I use my Econotig for general hobby welding, and I occasionally use it for my X-ray repair business. One problem that I recently encountered is I was trying to repair a broken metal bracket that holds a rear cover onto a Dental X-ray tube head. From the look and feel of the metal, I was certain that it was cast Aluminum, but I had a heck of a time trying to Tig weld it. The broken section of the bracket is only about 0.25 in wide by 0.125 in think, and about 3 inches long. The metal seems to be very brittle, as it breaks very easily when flexed even a small amount. When trying to Tig weld it, the metal just melts into a very rough looking blob, and will not accept Aluminum filler rod. After many frustrating attempts, I began to wonder if maybe the metal isn't Aluminum, and is rather Magnesium. So, could anyone please tell me how I could test the metal to determine if in fact it is Magnesium instead of Aluminum? BTW - I'm using pure Argon, with 1/16 inch Thoriated Tungsten.

Thanks!

[shorerider16]

Unless you are welding in a vacum chamber that has been purged, welding magnesium would cause it to burn, and boy does it ever burn. (I guess grade 9 science was good for something after all. )

[KBar]

(I guess grade 9 science was good for something after all. )

Back in the 60's we used to play with the different metals in science class. Our teacher would sneak in the back room and pull out his flask on occassion, we didnt see him for 15 minutes so we would play with different things, mercury was fun and we almost burnt the lab up. Yes, science was fun

[Xray]

Back in the 60's we used to play with the different metals in science class. Our teacher would sneak in the back room and pull out his flask on occassion, we didnt see him for 15 minutes so we would play with different things, mercury was fun and we almost burnt the lab up. Yes, science was fun

What else is there besides welding and riding??? Hmmmm..... I can think of one thing, but I might get kicked off this forum if I mentioned it!

[Xray]

Unless you are welding in a vacum chamber that has been purged, welding magnesium would cause it to burn, and boy does it ever burn. (I guess grade 9 science was good for something after all. )

Yes, I recall from High School Chemistry class that Magnesium does burn, but it requires Oxygen to support the combustion. I don't believe it would burn when shielded by the Argon.

[TS-Off-Road]

Unless you are welding in a vacum chamber that has been purged, welding magnesium would cause it to burn, and boy does it ever burn. (I guess grade 9 science was good for something after all. )

Magnesium welds fine. You need magnesium filler for it though. Don't leave any grindings or shavings laying around, those WILL burn!

[Randy Forbes]

Magnesium welds fine. You need magnesium filler for it though. Don't leave any grindings or shavings laying around, those WILL burn!

I agree. I repaired three (3) vintage go kart magnesium wheels yesterday. I've also done BBS (BMW) & Ferrari wheels. The BBS was a joy to weld on, quite free of contaminates. Ferrari and old McCulloch wheels are more challenging to get a porous-free interface of old & new.

The filler rod is expensive (last purchase $92/Lb.) but a pound goes a long way! Trick is to find a supplier willing to sell less than 10 Lbs!

I saved all the shavings from turning a repair (lathe swarf) in a paper bag and threw it on a bonfire. VERY bright white, but quickly burnt itself out. Don't try that in your shop! So yes, keep the area clean from shavings and grinding dust.

Magnesium oxidizes very quickly, so any repairs need to be cleaned back to bare metal. I usually use a carbide "tree" in a die-grinder for this. It helps to direct the chips away from your clothing.

[Xray]

I appreciate everyone's comments, but I'm still waiting for an answer to my question of how to dertermine what type of metal I have. I suppose I could shave off a few splinters of metal with a knife, and then try to burn it with a propane torch. If it glows very brightly while burning, then it probably is magnesium. Does anyone know of another way to test metals in order to determine what they are? I know with various grades of steel you could determine a lot about their makeup with a spark test by grinding them and seeing the color, brightness, and types of sparks that fly off. That basically shows how much carbon is in the steel. But what about testing Aluminum? Is there a simple test that can help you determine the type of Aluminum that you are about to weld?

[Burnt hands]

Xray,

You have picked a good quick method to test for magnesium with the shavings test. The camping stores have magnesium fire starters for just this use.

This should separate magnesium from alum.

I don't know of a valid method of determining the exact alloy type except thru the use of a Niton xray gun. This is very expensive equipment and I have nobody near me who has one.

I can offer this: if you determine your alloy is magnesium, I have a 3/8" thick plate of mg AZ31B. I will slice a piece off for you to try to tig weld if this helps.

If your piece is alum, it may be easier to find the proper tig alloy.
I defer to others on this forum for their expertise.

good luck

[migman69]

I believe you may want to consider some other kind of tungsten since i have heard this type is very harmful to your health without proper ventalation.