Sciencemadness Discussion Board

Thermite metal casting

ecos - 19-5-2016 at 10:47

Hi All,

I am planning to shape iron to form some metal shapes. melting iron needs high temperature "1538 °C". Making furnace and this stuff needs high effort

Fe2O3 + Al = Fe + Al2O3 + a lot of heat

I was thinking to use the molten output of the thermite reaction to draw my final shape under sand as this video : https://youtu.be/vCYICQ51tLA

I couldn't find any info about the quality of last product. would it porous ? has cracks?.....

did any try this before?

PHILOU Zrealone - 19-5-2016 at 11:26

Such thermite are/were used for railway welding / soldering of rails; they use special casting tools but the quatity of powder involved is much bigger (light powder mix --> big volume vs density of Iron = 7 g/ccm) than the resulting metallic piece.

[Edited on 19-5-2016 by PHILOU Zrealone]

Jstuyfzand - 19-5-2016 at 11:27

I dont think the end product will be nice and smooth, what metal shapes exactly?

Scalebar - 19-5-2016 at 12:40

Years ago i kept some iron from a thermite reaction, it was porous and crumbled after a few months - could be the amount of slag in the piece I'd got. What about using the heat of the reaction to melt an additional charge of metal? A jacket of iron pieces around a quantity of themite ( or vice-versa) might have some results - or just make shrapnel.

When it's used for rail welding i got the impression it was the heat of the molten iron flowing over the joint that caused a weld rather than the iron from the reaction filling the gap like solder

blogfast25 - 19-5-2016 at 13:02

Quote: Originally posted by Scalebar  
Years ago i kept some iron from a thermite reaction, it was porous and crumbled after a few months - could be the amount of slag in the piece I'd got. What about using the heat of the reaction to melt an additional charge of metal? A jacket of iron pieces around a quantity of themite ( or vice-versa) might have some results - or just make shrapnel.

When it's used for rail welding i got the impression it was the heat of the molten iron flowing over the joint that caused a weld rather than the iron from the reaction filling the gap like solder


It's perfectly possibly to obtain high quality Fe from thermite, also drop cast.

Rail welding by thermite is real drop casting.

Using thermite heat to melt another piece of metal won't work because heat transfer is slow and inefficient.

Shrapnel? Thermite isn't explosive by any serious description.

The video is of course a nice demo of how NOT to do it!

[Edited on 19-5-2016 by blogfast25]

ecos - 20-5-2016 at 02:31

I was planning to cast a knife or a small sword :) . just small things for fun.



macckone - 20-5-2016 at 20:00

Key is settling time before pouring. You need an alumina funnel with a seal. Adding degassers and fluxes helps.

PHILOU Zrealone - 21-5-2016 at 04:09

Quote: Originally posted by ecos  
I was planning to cast a knife or a small sword :) . just small things for fun.

Maybe inductive heating into a ceramic crucible would be more appropriate for that kind of metal art work.

[Edited on 21-5-2016 by PHILOU Zrealone]

ecos - 21-5-2016 at 14:24

Quote: Originally posted by macckone  
Key is settling time before pouring. You need an alumina funnel with a seal. Adding degassers and fluxes helps.


I am sorry, I don't understand your point.

macckone - 21-5-2016 at 21:50

Quote: Originally posted by ecos  
Quote: Originally posted by macckone  
Key is settling time before pouring. You need an alumina funnel with a seal. Adding degassers and fluxes helps.


I am sorry, I don't understand your point.

You can't just have the thermite go straight into the mold.
It has to have time to degas.
If it doesn't sit for a few minutes it will be porous and brittle.
Industrial thermite contained fluxes and degassers.
The mechanism for holding the thermite was traditionally similar
To a funnel made of alumina and a plug used to release the charge.
By holding the thermite in the flask until the reaction completes
And the degassers and fluxes have done their work.
Then the charge is poured.

PHILOU Zrealone - 22-5-2016 at 03:54

A little demo is better than a long writing:
Thermit welding used to join Railway tracks - Magic Marks

Practical videos:
Railroad thermite welding near the Mississippi river

Railroad thermite welding

macckone - 22-5-2016 at 19:40

Cool videos. I wonder what the plug material is. The flasks are fairly large for a relatively small amount of good metal, which is what we would expect.

ecos - 23-5-2016 at 15:00

Thanks for the info.

after some search. I found more info in this nice video : https://www.youtube.com/watch?v=TstoubOQImQ

MrHomeScientist - 24-5-2016 at 05:53

I did some thermite reactions once at a convention that also had some blacksmiths participating. I gave them a lump of thermite iron to play with, which of course felt solid and heavy, and they found out it was completely hollow!