DIY casting respect

[Julian]

Oh, meant to say ... don't know how you would ensure the MAPP gas cylinder was purged before attacking it with a grinder ... might be best to saw it by hand!

[Dickjotec]

As j says you will have problems with swar due to the oxides and cutting oil if used. Better to try som bits of stock. Make sure whatever you pour it into is dry and if metal hot. I have seen aly poured into a damp ingot mould go up and come down as very hot rain. A bucket of dry sand to put the dross into and to hold the ingot mould is a good idea.
Have a go it is not as dangerous as perhaps we are making it seem but do take care.

[julianf]

The reason i want to use swarf is simply as i have loads of it!

Ive got off-cuts also, so i could also try them and see what the difference is (they are the same grade).

Id like not to sound like an idiot, but im not too bothered by the danger aspect.

Ill tape down the trigger on my torch to drain what i can from the cylinder, and then see what happens...

[julianf]

We're burning coal today, as, would you believe it, ive run out of glycerol!

(we accquired the coal, so its not so bad ; )

Anyhow, ive chopped the top off the cylinder, and its in the firebox at the moment (empty) as i thought id see how hot it got (using my IR thermometer - which only goes up to 560c, but it will be an indication at least) and then how easy, or otherwise, it is to manipulate the cylinder in and out.  So, a dry run, if you will.

If it gets hot, ill put some metal in there and see what happens : )

[julianf]

Well, that did not take long - just looked in, and the whole base of the cylinder was glowing red.

Have now loaded it with a quantity of (damp with cutting fluid) swarf, and will see what happens next!

[photoman290]

watching with trepidation from a safe distance as Julians kitchen fills with oily cutting fluid fumes.

[Dickjotec]

It takes lots of swarf to make a usable amount of metal.

[julianf]

We went out, hence the lack of reports -

The swarf was dissapointing.  Although it all glowed red, it did not form a liquid.  It did somewhat bind together into a hard lump, which is now stuck in the bottom of the cylinder though.

Some of it i was able to knock out (dry crumbly stuff, that looked very much like it did when it went in, but dark grey, rather than silver) but the rest is still in the cylinder (i have not looked since it cooled though)

I then tried some a small offcut, which melted fine, pooling on top of the swarf lump at the base.  I tipped this (small amount) out onto a tray, and it looked as you would expect - a lump of metal, but probably only 10-15cc of it.


So, in conclusion -

Offcuts melt fine.
Swarf does not.  My hypothesis for this is that it oxidises (?) far too much whilst its heating.

Im wondering if this can be resolved somewhat by feeding it into a molten pool (rather than just trying with the swarf from the start) such as its bought up to melting point that much quicker.

But im wondering as to the dangers of doing this without it being properly dry first.


Its not like i have tonnes of the swarf - probably about 50 litres in volume.  It has minor value at the yard, so i could just take it there, but if that 50 litres gave me 2 litres of product, id still be happy.

Any suggestions?

[Dickjotec]

Probably the best way would be to do it under an inert gass. How to do it I don't know. One of the problems is that it does not weigh much so it is difficult to get much in the pot and it does not conduct the heat through so has lots of time to oxidise. You could try compressing it somehow before heating.

[Tony]

Dry casting?  Forget that, use plenty of water!

http://www.youtube.com/watch?v=WUVUYH_vvZE

[julianf]

Just gave it another go.

I started with offcuts, got a good pool at the bottom, and then added some swarf.

I was real dissapointed to find that everything in the tin seem to have gone hard.  And then i realised why...



That photo was taken in the basement of the reactor at Chernobyl, where the molten reactor core solidified into a structure later named as the "Elephants foot"

I have something similar (but a little less of concern to the world at large) in the ash compartment of the rayburn!


It seems small gas cylinders are not as tough as i had hoped.

[julianf]

...i suspect this may be the last time i try this stuff indoors.

(well, probably not, but ill give it a while anyhow!)

I think i will try and make a proper furnace using one of the oil fired boiler burners i have here.  Ive got a couple of gas cylinders (for the body of the furnace) but they are some way away.  Freecycle will provide though, im sure! : )

I need to find a better crucible also.  The aluminium was only on the cusp of melting when the MAPP cylinder failed, so it did not take much at all.

[Bill]

Your steel cylinder possibly failed as a result of a eutectic type reaction with the molten aluminium. Perhaps better to try with a ceramic type container or don't use thin steel containers more than once.

[julianf]

I have just read that iron is soluble in molten aluminium.  Id assumed this was only once it was at its melting point, but maybe not.

I should probably see if i cant acquire a proper ceramic crucible, and some matching tongs.


I have a load of night storage heater bricks about here.  By their nature, they are supposed to absorb heat, rather than insulate, but the are physically stable at higher temperatures (although the one in the firebox of the rayburn is falling apart)

Or i should just get a propane cylinder and do the job properly.

[julianf]

Coming back to this (ive been clearing out the shed here, and have much more brass than i thought) -


I understand that a reasonable lining can be made from perlite and fire cement (if i can get these things locally, im more likly to get them).  I think the ratio suggested is 4:1.  4kg of fire cement is about a tenner (toolstation), but, depending on the size of the furnace (obviouly!) ill need more or less than that.


Julian, you mention a 20 ltr tin.  Obviously i have a few of them, but i wondered about getting an empty propane tank off freecycle?  Something like this -



?


I wondered if the thicker metal wouldnt be easier to work with etc?  Less likly for all the grog to fall out at the first knock?



ps. i know this is taking me a while.  i have too many things to be doing at the moment as it is!