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4s2
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Thermite Welding
Sure everyone asks about how to make thermite etc, but has anyone done any in depth reaction testing?
I have heard that railroad rails used to be welded together with a simple thermite proccess. I want to try and work it with .25 inch plate steel on
some general joints. I also want to use it for cutting.
Also is there a better way to ignite the proccess without using a torch? I was planning on just using oxy/Acetylene at a distance (so not to blow the
powder away). I have heard of using some potasium compound with glycerol. Does anyone know what the K compound is, or where to find it OTC? (trying to
get away from using any kind of flame to start the proccess, so... no Mg)
The applications of using a practiced thermite compound for weldments and cutting is pretty amazing when you figure you dont have to lug your gas
cylinders around or a power supply for your plasma cutter.
Some other questions like... how do you think I could allow the puddle to move along the joint?(aside from gravity. I was hoping that I could string
the thermite out in a line and have it run straight down it)
What factors would allow control of the heat?
Would the Al2O3 be displaced to the top of the molten puddle? (the Fe will precipitate, and most flux metals rise to the top and form a slag crust, I
thought maybe the Al would do the same) If the Al stays in the weld, what might be a way to keep it out? Slag inclusion in any weld sucks nut.
I haven\'t failed, I\'ve found 683 ways that don\'t work. -- Me.
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Hardy
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Potassium Permangenate + Glycerol is a reaction of high enough temperature to ignite the thermite. (I havn't tried this.)
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Hardy
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I'm thinking of trying the thermite reaction this week if I can get my hands on some Magnesium, (or Potassium Permangenate + Glycerol, but I
doubt that)
I'll post Pictures if I can
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Hermes_Trismegistus
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Magnesium ribbon is fairly inexpesive and comes in long rolls,
to weld with thermite was a bit of an art form culminating somewhere around the turn of the century, best get a book on it.
Special crucibles were used to funnel the molten steel down into the joint, I beleive it was used not for convienience but because they were the only
way of welding some of the gigantic peices of machinery in common use.
paddlewheel axles and such...
For cutting, plasma torches are relatively inexpensive and vastly superior.
I know that gingery sells a book ( Lindsay's technical books ) on thermite welding.
There is a good reason that few people go beyond the play stage with thermite, using it is as a tool requires skill and the medium demands respect.
Failure to respect thermite will result in very bad things happening.
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Tacho
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Let me add to what has been said that the iron that comes from a thermite reaction may not be the most appropriate from a structural point of view.
And I would like to emphasize the word "art" mentioned by Hermes. Although I have never done soldering, thermite reactions are a very
special kind, and I believe that to get good results with soldering, one must "master an art" rather than just doing it straightforward.
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4s2
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I understand that there are better ways to do things, but I don't store those items in my truck (although I probably could) on a regular basis.
Something about driving around as a potential bomb (moreso than normal)
With thermite I could keep it in my truck(not mixed of course) and take it places that cylinders or electrical consuming tools could not go... say to
a junk/scrap yard. or... anywhere else that requires a quick cut. as well I wouldnt need to light ANYTHING on fire, as I would with Mg strips (plus I
can't find any where I live)
I found a possible sorce for the Potassium Permangenate, and glycerin from glycol or some first aid crap. I will search today and try to find it. If
anything both can be bought online.
As far as the Fe glob in the weld... Fe on its own is understandably not the best for welding steel, as their properties do not match. I had though of
including titania and cellulose into the mix to act as a shielding agent, as well the titania would be intoduced with the precipitate and form a
stronger weld.(faster)
I haven\'t failed, I\'ve found 683 ways that don\'t work. -- Me.
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flashpoint
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I have two questions, that I have had for a while concerning thermite.
1. Can you get 'sun burnt' from thermite?
2. Is the UV Rays, put off by the process of thermite burning, enough to damage your eyes?
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The_Davster
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I know the UV can damage eyes but I'm not sure if you can get a "sunburn" from it
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BromicAcid
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You can get 'sunburnt' from thermite, if not from any UV rays being produced then definately from the heat. Just as people around a hot
fire all day get 'sunburnt'.
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Hermes_Trismegistus
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Yes, you can get sunburn from anything emitting enough light or radiated heat energy.
Perhaps trying to locate magnesium ribbon might be worth the effort, glycerol and permanganate may make localized spots of high carbon (brittle)
bubbles
I'm not certain though, you see, the iron produced is at twice its melting point and carbon may be burnt away, the manganese may remain though,
you'd have to check it's boiling point.
P.S. You REALLY don't have to worry about any danger from mixed thermite.
Anything hot enough to get that burning would have........
Well, lets put this in perspective, a propane torch can't ignite thermite, a campfire.... can't ignite thermite, a fifty caliber bullet at
close range.....can't ignite thermite........ a blazing inferno of a housefire......can't ignite thermite.....
Okey Dokey Smokey.
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Hermes_Trismegistus
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Psst.....ebay..75 ft roll.....10 bucks
and you might be able to find it cheaper where you live, you can just ask for it at a chem supply, if you are asked for the intended use, tell them
the truth, thermite isn't controlled or restricted in any way, thermite welding is a completely normal and legal thing.
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IgnorantlyIntelligent
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Just a thought about you carrying buckets full of it in your truck.....I'd LOVE to see 55lbs of thermite burning in the middle of a road! 
But I know it wuldn't accidently ignite(unless I run up with some ribbon )
Hermes: Are you sure a camp fire can't ignite it? Hell I've used beer cans as fuel for fires while "campin" and had a fire so hot
we we scared of it(from only AL cans)
Thermite is a bit energetic and welding with it isn't very general. Maybe this would get more replies if it were in misc. or energetic mat.
[Edited on 11-4-2004 by IgnorantlyIntelligent]
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4s2
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| Quote: | Originally posted by Hermes_Trismegistus
P.S. You REALLY don't have to worry about any danger from mixed thermite.
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Yea I am pretty sure that even my burning vehicle would not ignite it, and if it did, I really wouldnt care becuase my truck would allready be on
fire... I added that to keep away posters that would think its unsafe.
Now then... I am either going to be purchasing some KMnO4 or Mg ribbon online.
I mixed up the propper amount of Fe2O3 and Al (that I grated off of a failed casting). I found some pure glycerin at walgreens. 4 oz for $2. The KMn04
that I bought was in the form of a fish tank somethiner-other(the bottle didnt give what % of KMnO4 it was, so I might try to concentrate it later).
It was a purple liquid. I put the KMnO4 on a paper towel and dropped on some Glycerin. oooo... not a lot happened. after about 5 min the purple turned
redish... but that might just do it on its own, or the paper towel could have absorbed it etc.
I tried it again, this time applying it to some Thermite mix, and same thing happened... nothing. at this point I lugged out my Oxy/Acetylene torch
and grabbed a double 0 tip.
I found that while the torch could easily make puddles in the chunk of steel I was working on, it would just as easily blow the thermite away. as
in... gust of wind, blowing away. it just scattered my pile. so I put the leftover thermite into a container(steel) and heated it again. I got some
rather neat sparks(that came out of the thermite area), but the thermite was so scattered I don't think it would have made a continued rxn.
Guess I will have to investigate the Mg. A friend said I might be able to find Mg at a gun/ammo shop localy? if not ebay is always cool too.
I haven\'t failed, I\'ve found 683 ways that don\'t work. -- Me.
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Marvin
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It has been suggested that the most reliable way to start thermite is with a sparkler, and that magnesium ribbon has a habit of going out. Ive seen
several failed thermite demonstrations where the magnesium ribbon has gone out without igniting it.
Mixed thermite is not that dangerous, but to ignite reliably it helps if the aluminium powder is as fresh as possible, so opening it when needed and
mixing would be best.
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Esplosivo
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The burning temperature of magnesium is around 310 deg Celcius, and probably a sparkler could reach somewhere around that temperature, though I
wouldn't suggest its use. I have never seen Mg ribbon which stopped burning in air (it burns as hell even in a CO2 atmosphere!!) and even if it
does fail why not simply stick another Mg ribbon and try again?! As far as I've understood his is not a demonstration right?
Edit: Btw, to collect most of the liquid iron, together with the aluminium oxide formed a crucible with a relatively small hole at the bottom is used,
probably some form of ceramic curcible.
[Edited on 11-4-2004 by Esplosivo]
Theory guides, experiment decides.
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Saerynide
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I dont understand how a tiny sparkler can set off thermite but a blazing truck can't If you are talking about the same kind of sparkler as I am, those little stick things that you can "write in the air" with
using its light at night, then I am really confused. The last time I played with those, it couldnt even catch my cotton shirt on fire (thank god  )
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Hermes_Trismegistus
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Um.....
I'm not certain as to whether a sparkler can ignite thermite, but if it was, I imagine it would be more widely known than it is.
Also, I beleive that the temperature of burning magnesium ribbon is actually 1335 deg Celsius (2435 degrees F), a little higher than had been
previously posted
And I understand that even that high temperature is just sufficient to ignite the thermite, and that sometimes doubling or trebling the ribbon
at the bottom part that is in contact with the thermite powder helps to provide enough thermal mass to get a high enough local hotspot for ignition.
as to the crucible you need to have the iron pouring out the bottom, don't assume you can use just any type of porcelain or clay, thermite will
destroy most, and i can't imgine you want liquid glass or vitrified porcelain in your melt.
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chemoleo
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Let personal experience speak, for a change :-P
Hermes, and whoever else is wondering/debating - sparklers are absolutely fine, and work well.
I don't know how many countless thermites I ignited with it (check Exotic Thermites thread).
I even managed to ignite an Fe2O3/Al thermite with Al-shavings, ranging up to 2 cm in length, and 2 mm in width (there you have to tie two or three
together).
Why does it work so well with sparklers?
They contain METAL powders, which produce the sparkles. They obviously burn at a high temperature, which is plenty to ignite the thermite.
In addition, the sparklers are STUCK into the thermite mixture (to provide a better heat contact), and it continues burning - unlike Mg ribbon, which
requires gas (O2, CO2, N2, you name) it to burn.
I am sure Esplosivos 310 degC was a typo, as even burning paper easily surpasses this temperature So must be yours, Hermes, Magnesium ignites at 632°C and burns at 1982°C (just checked)
The problem with the thermite welding is that the resulting Al2O3/Fe forms an intricate mix, and does not separate easily.
To avoid this, a flux agent such as CaF2 is added, which allows easy separation of the oxide and the iron.
PS the only problem with the sparklers I ever had was with CuO/Al, where a single sparkle is enough to set it off! And this burns instantaneously, so
be careful, else you will glowing copper gas in your face...
[Edited on 12-4-2004 by chemoleo]
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Esplosivo
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Sorry! Should have written 1310 deg celcius and btw it is an approximation as
you can note. Damn how much a number can make such a difference lol
Edit: This mustn't be my day. I've written the temp. as 310 again before the edit.
[Edited on 11-4-2004 by Esplosivo]
Theory guides, experiment decides.
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Hermes_Trismegistus
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I am curious to know the burning temperature of magnesium in air.
I did not use a reference book but rather used the internet. I looked again now and found two references to 1300 C and one to a higher temperature.
My only thought is that these temps are for air and one is for burning in a pure oxygen atmosphere.
Also I just re-read the beginning of the thread. 4s2..........I don't believe thermite is the appropriate tool for welding 1/4" steel plate.
I was used in the past to weld very large/thick objects (like railroad ties) but I'm pretty sure the process involved setting a crucible of
thermite above the gap between the peices to be welded and then allowing the molten metal to poured in with greensand or wooden molds to keep the
molten iron in the gap until solidification.
There might have been a process for welding thicker steel plate (battleship armor..etc) but thin steel plate would probably warp under the immense
heat.
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4s2
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Yes yes, we all know that thermite is not the best tool. I personaly feel that Oxy/Acetylene is a better tool (at least its more versatile, and
carries a high bang for the buck at $500) for welding and cutting. If you are careful you can easily weld quarter inch plate, weld brass, bronze,
stainless, Aluminum, cut etc.
What I want is a dry (or mostly dry) chemical compound that can easily be transported and used on the fly. If theres something better than thermite
(and isnt going to explode) that can be made instead, then by all means, I would be interested.
They used a crucible method with a flux to pour the iron into joints etc, but if the temp is high enough and it burns at the right rate, I predict
that it would be able to create a small puddle in the base metal(after the plate heats up (after a few inches of rxn)) while the small puddle is
open, fluxes would help bring the Al2O3 to the top of the weldment, and Titania or something like it would be added into the precipitate of the weld
to strengthen it.
If the end result could be hardened rods that could be pulled out on a whim in an isolated condition (such that any kind of welding equipment is not
possible).
I guess I dont understand why no one understands that you can't just whip out or easily store gas cylinders in your vehicle(Plus the DOT would
have my balls becuase I have an SUV not a truck)
And unless you have a giant alternate alternator, for your special 12 V arc welder... (although I have seen this where they step it up to 110v on a
jeep)
I know the marines have some sort of coumpound that can be used to cut, and or sloppy weld, does anyone know what that is?
[Edited on 12-4-2004 by 4s2]
I haven\'t failed, I\'ve found 683 ways that don\'t work. -- Me.
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chemoleo
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Hermes, 1300 deg C is way too low. The light, at that temperature, would still have a yellow tinge to it. While, as you should know, Mg burns with a
brilliant white flame... suggesting a large UV portion in it. And this means the temperature HAS to be >1600 deg C.
If they burnt it in pure O2, they would have said.
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Hermes_Trismegistus
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bliss....
Approximate temperature (°C) Color observed
525 faint red
700 dark red
900 cherry red
1100 dark yellow
1200 bright yellow
1300 white
1400 blue white
These are references for magnesium burning temperature.
This one is a chem teacher listing it at 1335 deg C (for burning Mg Ribbon)
http://kaffee.netfirms.com/Chem/Burning.Mg_Demo.html
This one is a chinese magnesium manufacturing plant listing it at 700 - 1000 degrees celcius (for burning Mg Granules)
http://www.mhmqh.com/cpjs/ml001.htm
This one lists the exact temperature you are quoting and so leads me to beleive that this is the one you source you used.
http://www.emedicine.com/emerg/byname/cbrne---incendiary-age...
And then there is this British one which supports 1335 deg C as the the burning temperature of magnesium.
http://www.chem.leeds.ac.uk/delights/texts/Demonstration_20....
THis one lists it as >5000 degrees fahrenheit.
http://www.immnet.com/articles?article=1418
In short, it appears that there is no consensus as to the burning temperature of magnesium.
It leads me to believe that the burning temperature varies, perhaps due to the form or size of magnesium particle/ribbon/ingot being burned.
However that is just a supposition. For a final word I'd of course prefer to consult the CRC handbook when I have the opportunity.
P.S. get stuffed.
[Edited on 12-4-2004 by Hermes_Trismegistus]
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chemoleo
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Lolz good to see people read what I write, with Argus eyes
It seems there is quite a bit of dis-consensus in the literature, good thing we get clear on this.
Let's make some consensus here (same as you):
The temperature of burning Mg wildly depends on conditions, ranging from 1300 --> ~1900 deg C (700? I never saw Mg burning 'cherry red'
). I wasn't aware of that, that ribbon/granules/1kg blocks give different
temperatures...allthough now, that I think of it, it makes sense.
As to colour vs temp - I found the same data as you, but remembered incorrectly. My bad 
It just strikes me that the burning temp is quoted to be sometimes that low - not for no reason Mg (or Al) is quoted to burn with a VERY hot flame.
1330 deg C is just a few hundred deg above molten iron... plus, I was thinking in terms of thermites, where effectively Mg/Al is burning, and this
easily reaches 1800 deg C - despite the fact that the oxide has to be reduced, which entails an inherent energy loss (the oxide being reduced to the
metal). Admittedly this is still not the same as burning it in air, so this probably explains my confusion on this.
Anyway, back to topic (and no more needless accusations pls )
[Edited on 12-4-2004 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
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Mr. Wizard
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Some thoughts on welding without gas containers. You can use your car or truck alternator to weld, You can even use a few car batteries connected in
series. I won't give details because a search of the internet will turn up all you need, with pictures, equipment, and examples. It isn't
the ideal, but it will work. Since this is a thermite thread I'll throw in that it is possible to ignite fairly course thermite with a hot wire
with a car battery and jumper cables. Fasten 6 inchs (150 mm) of 1/16" (1.5 mm) flexible steel cable to some heavy copper cables. Jumper
cables work well, and have the clamps on them already. Bury the steel wire in the mass of the thermite and when you want to ignite it just connect the
cables to a charged automobile battery. Use the standard precautions you would observe when working around car batteries, gasoline, and electricity.
It is possible for the car battery to explode if you draw too much current. This won't work with small one inch (2.5 cm) piles of thermite, but
it will on larger ones. Don't stare at the glowing metal, it will leave spots in front of your eyes.
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