I don't know, but I had the same thoughts about melting down brass taps and fittings etc. Is it worth the gas ?

Hi Alan,

I have tried melting aluminium cans. The main problem is that being thin the cans have very high surface area to volume and when melted there is a great deal of dross and a corresponding low recovery of usable aluminium. Recovery is slightly better if you use Lo Salt as a flux.

Cans are also made from pure aluminium. This is very soft and gummy so it does not machine well. Adding a little copper (circa 2-4%) improves the machinability of the metal.

Speeder builder5. I think you would get a good recovery of brass from scrap taps and fittings.

Mike

I find scrap aluminium everywhere. Possible sources are old carpet joining strips, old aluminium furniture, old shower rails, old car wheels, old hard drives etc.

The advantages of aluminium are that it is plentiful, it melts at a relatively low temperature (circa 650 degrees C) and it can be melted in easy to find stainless steel containers. Furnace construction is not critical because the temperatures are fairly low.

Once you move to melting brass then the melting temperatures are much higher (circa 1000 degrees C). The furnace construction is more critical, special clay graphite crucibles (expensive) need to be used and zinc fume (toxic) is troublesome. The potential dangers of the process are large.

I would advise try aluminium melting and casting first and then move to brass once you have some experience.

Mike

Michael, I'd be wary of old car wheels, they could be magnesium, hence the term 'mag wheels'

should burn well tho.

Roy

Hi,

This guy does a lot of home casting for his engines and his self made videos are well worth watching. This is what he has to say on recycling aluminium for casting (including a simple test for magnesium in alloys):

I think the video is showing that the larger the surface area of the scrap Ally the less you will get in the actual melt due to the surface oxidising.

This is why ally turning have so little scrap value, to high an oxidxe content.

peter

What are ready-meal food trays made from? I tried melting a couple (just with a torch) as an experiment, and they just turned to dust. Could it be some coating? A storey on the radio I heard:- Some Aussie is reconned to be the biggest lager drinker/ most for longest time, it was calculated that if he'd kept all the cans the scrap price now would have paid for his beer over all the years.

Brian:

If you have a spring balance and a bucket of water, you can determine the specific gravity of the casting. This is an up-to-date version of Archimedes 'eureka' method.

Weigh the casting hanging in air and then weigh it again immersed in water. It will lose the weight of its own volume of water. The specific gravity is equal to the dry weight divided by the difference between the dry & wet weights.

Suppose it weighs 10 kg in air and 8.5 kg immersed in water, then the specific gravity is equal to 10/(10-8.5) ie 10/(1.5) = 6.7 (This example doesn't apply to a real metal – I've just used easy numbers to show the method of calculation.)

Then look up the SG on the internet or in some Tables of Physical Properties. This method will distinguish easily between aluminium and the zinc-based die-casting alloy (aka 'Mazak&#39. I think pure zinc castings wouldn't often be encountered, Mazak would be more likely.

If you don't have a spring balance, you can use a rod or beam and a counterweight, with bits of string to suspend the beam itself and the casting and counterweight from the beam. You measure the distances from the beam pivot to the casting's string at the balance points dry and in water (keep the counterweight in the same position and move the casting to balance in each case. It's a bit more difficult to explain in a forum like this but by manipulating the two distances, you can calculate the SG.

I hope this helps.

Best regards,

Swarf, Mostly.

Dithering,

Thanks for the input – I mentioned about this happening because there was a suggestion earlier to use stainless steel cans for smelting, – I wanted to point out that this is a dangerous practise. When I first started, I thought stainless cans would be just the thing. I did not know at the time, and would have found it hard to believe that ally at 650 degrees would 'dissolve' or otherwise penettrate stainless steel -The first one lasted for about three smelts, then dumped ally – fortunately inside the furnace, so no harm done. The second one I tried failed at the second attempt, and dumped ally around my feet – I was very glad I had boots on – it also boils the moisture in concrete, which spits violently. The same phenomenon occurs with the chunk of copper suggested in this thread to make the metal easier to work – copper melts at a much higher temperature than ally (my forge certainly won't melt it), yet there is no trace of the lump of copper in the resulting ingots – it dissolves (or otherwise merges) into the ally.

I mention this again, because someone in this thread suggested stainless steel cans for smelting, and the thread seems to have missed that point completely. I use a thick homemade iron can, with a coating of clay inside. Even for 4 cans for a pound, its not worth the risk with stainless.

I have used many old harddrive castings for smelting – so far all of them have been aluminium.

Has anyone reading this forum actually used rubbish metal like drinks cans or picnic trays to produce useful castings with any sort of bulk? – I always had far too much dross, as many people also say in this thread (and on many other threads, over and over again) – IMO, it simply is not worth the time to collect the damn things, then melt them down, then decide what to do with the resulting crap, 'cos it sure isn't useful metal. There is a thread somewhere in this forum (I think) which discussed this long ago, with some interesting details on metal thickness and coatings – the opinion then was forget it.l

Mike Cox is hiding his light under a bushel – it's worth finding his artilces in MEW near the end of last year on aluminium smelting. they certainly make me want to have a go at it.

Neil

Michael,

I  also have been making castings for many years, and I just have to disagree with you, if only for safeties sake – Many sites dealing with aluminium mention the risk of using steel containers – the failures I have had were not  'pinholes' – large areas of the steel disappeared with no warning – cleaning/heating them does no good. On the other hand, crucibles can usually be seen to be cracking, and therefor avoided. As I noted, I use a thick steel can with a clay liner – so far that has survived for about three years – no cracks, no failures, no risks.

 Of course, you are free to take the risk – but at least others should be aware of the risk of getting molten aluminium at 700 degrees on their feet.

This thread has covered most of this stuff before, including comments from current contributors.

http://www.model-engineer.co.uk/forums/postings.asp?th=45889

Edited By wotsit on 24/02/2012 10:33:31