Welding magnesium...

Certainly magnesium can be welded. It is however VERY combustible and extremely hard to put out if it catches fire (ever try to blow out a road flare?).

 

Wow...this is timely. I have a set of 308 magnesium Cromodora wheels in which one of the wheels has a 1cm chunk taken out of the perimeter of the wheel. I'd like to have it repaired, but have been having some difficulty in finding a place that will weld magnesium.

Does anyone here know of a reputable wheel repair shop that will weld magnesium?

 

Product liability has made many shops skittish about any serious repair on a wheel especially on a performance car. Doesn't sound like a big problem to fix (as long as it doesn't burst into flames). Keep plugging along, perhaps you can find someone who doesn't have a business to protect that can weld it.

 

... unless you eliminate the oxydizer.

Traditional magnesium welding was done in an inert atmosphere -- pure nitrogen or some "noble" gas from the periodic table. That required a "glove box" enclosure for small jobs, or an environment suit for working in larger enclosures.

Environment gear for sand and grit blasting has become more common. But I've noticed that people have been just "playing the odds" with magnesium, lately. The shop that cleaned up the Alfa's wheels also just went at it with a grinder in plain air.

Maybe because aluminum alloys are more common. Aluminum is harder to ignite -- but playing with "Thermite" doesn't sound like such a great idea. I messed about with burning magesium in my youth enough to know to treat it with caution.

 

Not trying to be discouraging, just relating what has happened around here. There used to be a wheel shop in town that would fix anything you brought in (good work). Now I hear they don't even want to look at cast wheels.

That's not the only game in town but it makes you look harder to find one.

 

check these people out to see if they can do mag:
http://www.rimpro.com/

 

Looks promising, they tell you up front to expect a six week wait.

 

Shavings only...? huh

We used to throw old VW blocks into our beach campfire.

It always brings the rangers though... never had one explode. I guess it could... raining molton Mg...

 

1. Several years ago I found a pro welding shop that would weld my VW engine case, just had to clean it up for them. I can see wheels being a different insurance/safety matter all together, though.

2. One of my good VW buddies was grinding on his VW engine case -- lots of dust in the air. He was using an electric grinder, hand-held. Next thing he knew, his upper torso and head was engulfed in a ball of fire. He lucked out, only a small loss of skin hair and 1st/2nd degree burns. He looked bad at first but it's been over a year and he looks normal now. But we all learned...

3. Another VW buddy, retired certified VW mechanic, used to work on the engine cases as well as throw them into camp fires. Heat works either way

 

Kids remember,,,,,,,,,,



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I did some magnesium machining in college, working on Mg control arms for our Formula SAE car. Being engineers we had to be responsible and collect those shavings for future experimentation. They actually were not easy to set on fire, eventually had to get it started with some paper. Then add a shot of water to kick it up a notch, bam! And always wear safety (sun) glasses, burns nice and bright.

 

There are any number of Magnesium Hewland gearboxes out there that have been welded. I have welded/repaired mine with no problems. I would guess it's almost impossible to get a Mag casting to burn with a TIG torch.

 

Well pardon the heck out of me for disagreeing with the Oracle of All Things who is obviously Always Right.

--- obviously a statement intended to dazzle the reader with your all-encompassing expertise.

http://www.sylvaniamaterials.com/pdfs/Welding_Poster.pdf: "Since magnesium will absorb a number of harmful ingredients and oxidize rapidly when subjected to welding heat, TIG welding in an inert gas atmosphere is distinctly advantageous. The welding of magnesium is similar, in many respects, to the welding of aluminum. Magnesium was one of the first metals to be welded commercially by the inert-gas non-consumable process (TIG)."

http://www.welding-advisers.com/Welding-magnesium.html: "Safety precautions must be understood and followed. When Welding-magnesium or when working with magnesium one must always remember that the material is highly oxidizable and, when in form of machined turnings or powders, it will burn, if ignited, with dangerous intensity. Machining must be performed under controlled conditions, with approved extinguishing agents ready on the spot." ... "Gas Tungsten Arc for Welding-magnesium (GTAW) also known as Tungsten Inert Gas (Tig) ..."

http://en.wikipedia.org/wiki/Arc_welding: "Gas metal arc welding (GMAW) is a semi-automatic or automatic welding process that uses a continuous wire feed as an electrode and an inert or semi-inert shielding gas to protect the weld from contamination. When using an inert gas as shield it is known as Metal Inert Gas (MIG) welding. ..." ... "Gas tungsten arc welding (GTAW), or tungsten inert gas (TIG) welding, is a manual welding process that uses a non-consumable electrode made of tungsten, an inert or semi-inert gas mixture, and a separate filler material."

http://en.wikipedia.org/wiki/Gas_tungsten_arc_welding: "C. L. Coffin had the idea of welding in an inert gas atmosphere in 1890, but even in the early 1900s, welding non-ferrous materials like aluminum and magnesium remained difficult, because these metals reacted rapidly with the air, resulting in porous and dross-filled welds.[2] Processes using flux covered electrodes did not satisfactorily protect the weld area from contamination. To solve the problem, bottled inert gases were used in the beginning of the 1930s. A few years later, a direct current, gas-shielded welding process emerged in the aircraft industry for welding magnesium.

This process was perfected in 1941, and became known as heliarc or tungsten inert gas welding, because it utilized a tungsten electrode and helium as a shielding gas. Initially, the electrode overheated quickly, and in spite of tungsten's high melting temperature, particles of tungsten were transferred to the weld. To address this problem, the polarity of the electrode was changed from positive to negative, but this made it unsuitable for welding many non-ferrous materials. Finally, the development of alternating current units made it possible to stabilize the arc and produce high quality aluminum and magnesium welds.[3]"

Note the terms: MIG -- Metal Inert Gas, TIG -- Tungsten Inert Gas. Prior to the widespread availability of MIG and TIG welding equipment, welding in an enclosed inert atmosphere was the only available option.

Take an old-fashioned oxy-acetyline torch to your filler rod and see what happens.

Did you miss the term "traditional"? Did the universe not exist before you were born? Do you share Neanderthal's inability to comprehend the passage of time?

"Magnesium welding -- So easy a caveman can do it"


And if you would notice, the comment I took exception to was:

http://www.ilpi.com/safety/extinguishers.html: "Those who work with flammable metals may also have a specialized Class D dry powder extinguisher for use on fires (in a pinch, a bucket of dry sand will do, but you really should have a Class D unit if you work with such materials)."

But then, Class D fires weren't even defined in the 40s.

 

Randy,

THanks for an informative post. I agree with what you wrote - magnesium is extremely hard to ignite, in my experience. I remember being able (barely) to ignite the thin strip using a cigarette lighter when younger - but it required getting the hottest part of the flame right on the thinnest part of the metal, not that easy. Years later in our shop I had a relatively thin rod of the stuff and I just could not light it, even with a MAPP torch. I am not sure I believe the story about throwing Mg engine blocks into a fire - they would never light at that heat level and if they did they would burn ferociously hot and for a very long time. And it's not like large chunks of Mg alloy are easy to find, let alone pure Mg (and they sure aint the same thing).

Good job on trying something that many/most folks would be paranoid to try




DGS,

"Note the terms: MIG -- Metal Inert Gas, TIG -- Tungsten Inert Gas. Prior to the widespread availability of MIG and TIG welding equipment, welding in an enclosed inert atmosphere was the only available option.

Take an old-fashioned oxy-acetyline torch to your filler rod and see what happens."

The whole point of MIG and TIG are that there is no O2 in the gas mix - to prevent oxidation. To get ideal welds in Mg (and many other metals) you back fill the part with gas so you get good penetration all the way through. I'm sure an Mg rod will burn with an Oxy-Acetylene torch, so will Al if you get it hot enough... but a huge chunk of Mg alloy in a campfire won't

 

When I was in the Navy, if there was ever a Class D fire, we were told to "eject it over the side". The ocean was our "fire extinguisher"

 

My experiences are from back in the '60s when TIG welders weren't stock items at Sears. We used a glove box and an argon atmosphere for welding. We weren't welding huge chunks, we were welding slot car chassis parts -- which were thin enough to be ignited readily. My cousin was more into the Mg frame cars -- I preferred the downforce of heavier brass rod birdcages with big honkin motors. His preference for Mg frame cars caught up with him when he tried affixing a model rocket motor for propulsion.

But elemental Mg ignites at 632C and melts at 650C -- although different alloys will vary significantly. (http://www.freepatentsonline.com/6818075.html) While shapes with more surface area exposed to an oxydizer will react more readily, and smaller masses will increase temperature from less calories of heat, the shape of an object doesn't change its flash point temperature. Just because an alloy doesn't light off in a TIG arc doesn't mean it can't be ignited.

In the comm stations, we had thermite charges on the crypto gear -- if the site was overrun, we'd light off the thermite, and the whole rack would melt down -- right through the aluminum floor. We called it "China Syndrome".

 

I agree completely, however I think it's more than just the shape, but the size. Maybe it's hard to get one part of a chunk of Mg hot enough to burn because the heat is transferred so quick through the part? I dunno... but I know the problems we have at the shop with TIG welding or plasma cutting Aluminum are due to this. My welder will do twice as thick steel as it will Aluminum. I'd guess thats why igniting chunks of Mg is much harder than small shavings. Also, many metals will burn - including aluminum and titanium. Mg more easily, for sure, but the others will too (and often equally as ferociously as Mg). The thing is, Mg has this 'mystical' reputation for being deadly - like some think it will burn as easy as a gas soaked rag! Not saying you feel this way, but the rep of Mg has many people thinking this way.

Kudos to the guy for giving it the ol' college try, and succeeding! I think its very safe to say that if you work Mg (be it milling, lathe, grinding, cutting or welding), make sure you set things up so that if it DID catch fire, it could be allowed to burn itself out without major damage to person or property. This means not grinding a big chunk of Mg on a metal table where it would just melt through but working Mg near the shop door on a concrete floor away from too much flammable stuff would be OK.

On a side note, I got an email from a machine broker once... he had a milling machine for sale cheap that had "some fire damage". Turns out a block of Mg had ignited on the table and of course could not be put out. There was literally a funnel shape in the machine right through the table and to and through the casting where that Mg had burned and burrowed its way down before it went out. Expensive lesson to learn

 

Originally Posted by Randy Forbes; "........ you intentionally wanted to wreak havoc and destruction."

Sorry Randy,
But if'n you don't want a Witch hunt,,,,, then leave your broom parked outside.

Edwardo
I got an A+ in TIG at my University,,, I can weld anything.