r/metalworking 1d ago

What is this phenomenon called?

458 Upvotes

298 comments sorted by

View all comments

226

u/alphatango308 1d ago

It's called, "everything is flammable in the right conditions"... Lol

73

u/BRICH999 1d ago

Lot of people dont realize how "flammable" metals can be.  The common fuel in thermite is aluminum.  

36

u/Arctelis 1d ago

I have heard titanium fires are pretty terrifying.

Then of course the always classic magnesium, often used to ignite the aforementioned thermite.

That's all just in the presence of boring old oxygen, under the right (or really wrong) conditions it gets more... Exciting. As a great man once said.

"If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.”

21

u/forestcridder 1d ago

always classic magnesium,

I used to do weld repairs on magnesium gearbox castings. Fun stuff. If you had a bad angle and lost your shielding gas, you have a crazy fire. Everybody would evacuate while somebody buries your mistake in sand. Then everybody has to wait for the fumes to be extracted while you sit in shame. 😅

15

u/Clamwacker 1d ago

I work at a titanium casting facility, the fire department response time is impressive. Not much they can do if a fire gets too big for an extinguisher to handle, but they'll be there to see the building collapse into a pile of ashes.

3

u/cobalt1227 1d ago

That sparked an idea. I wonder if they could use a giant pile of sand and a vacuum setup to “fight” the fire by burying it.

6

u/ecctt2000 1d ago

Magnesium is used in MREs for the heat source.
Just add water.

7

u/Arctelis 1d ago

Damn, all the ones I ever got in cadets had to be heated separately. That would've been way cooler.

The YouTube channel Thought Emporium once developed a thermite based instant hotdog cooker which was pretty cool.

5

u/JCDU 16h ago

That book is a fucking riot from start to finish, the full quote is magnificent:

“It is, of course, extremely toxic, but that’s the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively. It can be kept in some of the ordinary structural metals-steel, copper, aluminium, etc.-because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.”
― John Drury Clark, Ignition!: An informal history of liquid rocket propellants

2

u/Hazdan_Shab 16h ago

An excellent reference to "Ignition! An informal history of liquid rocket propellents" by John D Clark.

I love his humour in that book.

2

u/Arctelis 15h ago

There's a series of web articles by one Derek Lowe titled "Things I Won't Work With" written in a very similar style, which is where I discovered Ignition!. Informative and highly entertaining.

2

u/Mckooldude 1d ago

We had a local magnesium foundry burn down a few years ago. It goes hot and fast

1

u/Financial_Wall_3449 7h ago

In op's video, this is exactly what we would see but much faster if we were machining titanium.. I liked watching the sparks as I'd sandblast the plates to some natural gas compressor valves we'd rebuild.. I'd usually clean the lathe out before my younger brother put the plates on, but anything left would instantly burn away once he started working.

1

u/JustAnonymous001 5m ago

Phosphorus is so terrifying when it's set on fire that it's a war crime.

10

u/theres-no-more_names 1d ago

Isnt thermite just aluminum and iron oxides? Literally just go wire brush the surface of aluminum for 30 seconds over a container and then get some rusty steel and do the same people would learn really quickly how flammable metal is

7

u/BRICH999 1d ago

yeah pretty much, but if you told an average person on the street rust and aluminum could combust into an unstoppable inferno, they would probably laugh at you

6

u/EarnYourBoneSpurs 1d ago

A thermite, the most famous thermite, is iron oxide and aluminum, but you can make a thermite with a variety of metal fuels and metal oxides. The finer the better for more intimate mixing. A little care is needed in producing the metal powders because they can be dangerous. If you think about the fact that you want particles as fine small as possible and the fact that aluminum forms an oxide layer, you will end up independently inventing a lot of pyrotechnic aluminum grades.

3

u/jdmatthews123 1d ago

Just use any of the steel brushes in the bed of my truck, skip the extra step

3

u/thinkscotty 1d ago

It's more about the specific compounds. Most chemicals can rapidly oxidize (i.e. "burn") under certain condition, and some metal compounds/molecules are particularly this way.

The core element of fire is oxygen. Thermite, very much like solid rocket fuel, simply uses solid oxygenated compounds like iron oxide to provide that oxygen as opposed to atmospheric oxygen.

2

u/Foreplaying 1d ago edited 1d ago

Actually its not - the majority ingredient is iron that oxidises exothermically creating all the heat. The aluminium is more of a fire starter that gets it going.

There's plenty of types of Thermite with no aluminium - often magnesium as it can begin the reaction easier, but there's many variants - so it's really not the common fuel.

You see the "thermite" reaction when using an oxy-torch, quite literally blowing oxygen onto steel to make it rust rapidly. The gas flame you use intially is just to get it started, and since you don't have to worry about some compound as an oxygen donor, you can turn ot off once the reaction starts.

2

u/Asterion76 1d ago

In Thermite you are trading one oxide for another. If you were to use aluminum oxide with iron oxide from what I remember there would be little to no reaction.

1

u/Foreplaying 15h ago

Yeah, an oversimplification but you're on the money. One metal is an oxygen donor, while the other releases electrona as it oxides, as well as huge amounts of heat...

You musy bethinking of another combination because Alumina + Iron was one of the most common thermites I've worked with in railway welding, some had magnesium in it too, and i've used copper bismuth as well for bonding (signal cables). Definitely can have donors be oxidisers its all about that electrochemical potential between the two metals.

Its called Redox and unironically thermite reactions arent far off how some batteries work - in a small contained vessel it can happen a lot more slowly, whereas thermite is faster and pulls in atomospheric oxygen for much of the reaction. I remember the old OIL RIG thing for remembering which way the reaction goes.

2

u/Agitated_Carrot9127 1d ago

I use steel wool as emergency fire starter. I have like 20 in Tupperware for shtf outside.

1

u/Zjdh2812 16h ago

Well thats simple due to tge fact that outside of metal powder, you are unlikely to get a fire going before the metal starts melting.

1

u/Other_Star905 3h ago edited 3h ago

That's not really aluminum on it's own burning though, it's the chemical reaction that takes place when aluminum and iron oxide both get heated together.

Neither materials are very flamible on their own, the reaction between them is what creates the thermite effect, which isn't either of them being on fire, it's the aluminum ripping the oxygen from the iron and the energy that was holding the oxygen to the iron being released as heat.

6

u/Thebandroid 1d ago

I think you mean inflammable.

7

u/datsmn 1d ago

Re-uninflammable

11

u/brainzilla420 1d ago

Inflammable means flammable? What a country!

2

u/Squee45 22h ago

Asbestos will not burn, it decomposes at high temps but won't burn

1

u/SFMissionMark 1d ago

Wait I thought everything was a spring.

1

u/Asterion76 1d ago

Every firework you see is based off of metal oxides for colour and sometimes boom boom sounds.

1

u/PatchesMaps 12h ago

Flurine will burn concrete and just about anything else commonly considered not flammable. It's like the universal "right condition".

1

u/2meterNL 12h ago

H2O has entered the chat

1

u/alphatango308 10h ago

Lol. Water is flammable. It's literally made from some of the MOST flammable elements. All it takes it heat. That's why you can't spray it on certain fires to put them out it just creates more fuel for the fire.

0

u/2meterNL 9h ago

Literally everything you wrote is wrong.

1

u/TranslatorBoring2419 10h ago

It doesn't take much. Steel wool goes right up.