Melting aluminium sheet metal comparison.

[100model]

So what I found out making this video that different sheet metals can give widely different recovery rates and some machine really well to very poor machining without cutting fluid.

 

[lee webster]

If I want any sort of aluminium ingot here in Cornwall, I have to send for it. Very expensive to buy and post. If it was only for decorative items, such as a small picture frame I cast last year, I would use any source of available scrap. The picture frame was cast using a scrap Austin Seven starter motor housing (badly broken and badly welded). My sand rammer which is well used was the first thing I cast and is made from cans and extrusions. I have no idea what it's like inside, but it works perfectly. Any important castings I will use proper ingots. I wouldn't use cans anymore because of the fumes and smoke. I melt in my garage, which is joined to the house.

 

[ddmckee54]

I've always heard that any extruded aluminum, or sheet aluminum, will be more gummy when melted, cast, and then machined. Not to mention produce more dross when melted. Car or Truck pistons, wheels, or any other parts that have already been cast, are a better source of metal for casting parts that need to be machined. I think it has to do with the silicon content but I'm not sure. The already cast parts will already have it while the extruded parts will not.

The casting forums recommend that the best thing to with the extruded stuff is sell it to a recycler and buy the good stuff.

Don

 

[lee webster]

Getting "proper" aluminium ingots is very difficult, unless you buy dozens of kilo's. I haven't found a reputable supplier of LM25, but I can buy ZL12. Other casters use car wheels. I have been advised not to. Apparently a car wheel is made by die casting and is a different type of aluminium to that used for sand casting. I didn't have much luck with a Renault wheel, but I was having a bit of trouble with my small electric foundry at the time, so it could have been me. One stockist offered to sell me several kilo's of LM25, but I had to collect them. He is 350 miles away, and it was in the middle of lockdown. I didn't take him up on the offer. If anyone in the UK, preferable the south west, can recommend a supplier, I would like to know about them.

 

[Vietti]

I wonder if you could put together a group buy with the other casters in the UK?

 

[lee webster]

It would be interesting to see how much an order for the minimum amount of ingots would be, and who would be interested in buying them. I think most casters are happy to use car wheels, or other aluminium car parts.

 

[100model]

Getting "proper" aluminium ingots is very difficult, unless you buy dozens of kilo's.

It is the same where I live so because of that I have always used scrap and have never purchased ingots. I have used wheels all the time and give great results. I was surprised how well the cans machined but the heatsinks needed cutting fluid and then gave a really good surface.

 

[Steamchick]

I just melt cans, swarf, thick foil, etc. other aluminium to make "scrap" bar for screwdriver handles - or whatever. But hammer it tight and drop it into the molten aluminium in the pot while it melts - submersed - and I manage to get away with some useful billets for machining. I don't cast parts in moulds... failed miserably when I tried a flywheel in Mazak.
Interesting thread finding out all the things I do that are wrong.
Thanks guys.
K2

 

[lee webster]

I think my failure to get good results from car wheels was more down to me than the metal. I have felt for a while that my foundry isn't getting up to temp as well as it should. A Mk2 is on the "long winded" drawing board.

Swdweeb posted a video on youtube recently describing how to weigh a cast piece to determine if it has any inclusions. I tried it with a few pieces. Very interesting.

 

[Nick Hulme]

I donate my scrap and chips to a school, the teacher says he likes it because it's oil free and casts better than anything else he's had, it's all 6082, but there are many different grades of "Extruded" and referring to them all as one is not a smart move

 

[DaleW]

It all depends on what you want to do with it. If it's for machining then you want something like a 2011 which has 5-6% copper in it, a little led and less than 0.4% Silicon. If it's for welding than something in the 6000 range. 6060 for example has between .3 - .6 silicon as well as magnesium, this one is common in window frames, doors, pool fencing etc. As you remelt you will loose elements such as silicon, there by changing the properties. Ornamental casting can be pretty much anything but if it has a specific purpose I would do some research into what specification is used for that purpose and go with the specified ingot. On average clean ingot can be poured in the low to mid 700c where scrap aluminium flows better around 780c

 

[awake]

A couple of questions which will reveal both my interest and my ignorance on this topic:

1) Would the machining properties of these various ingots be improved by "tempering"? I confess that I don't actually know what that term means with respect to aluminum, but I'm aware that some grades of aluminum are miserable to machine when untempered, but well behaved when tempered ... or something like that.

2) Is it possible to add silicon or other alloying ingredients to the melt to improve the properties? I have seen videos with cast iron where the caster adds ferro-silicon (? or something like that) to improve properties.

 

[DaleW]

yes you can temper Aluminium (reduce it's hardness) and heat treat it but it depends on what grade of aluminium your using as this determines the temperature, how long it's held at that temperature and then how it's cooled. The difficulty comes in, unlike steel or cast iron, you don't have a changing colour to give you an approx temperature which is critical and not all grades can be heat treated. this is all part of the science of metallurgy though I prefer alchemist.
Your second question is most definitely you can add other elements to your melt, but you really need to know what your starting with first. Cast iron generally you will always add some carbon (graphite) and silicon as these will burn off during the melt and again depends on what your starting with as many of the different grades of cast iron are dependent on the percentage of carbon and silicon in the mix.

For the average backyard foundryman go forth have fun stay safe and melt but if your doing critical parts for your miniature stream train, traction engine and so on be very careful as the wrong grade of material being used can have disastrous consequences.

 

[Richard Hed]

I just melt cans, swarf, thick foil, etc. other aluminium to make "scrap" bar for screwdriver handles - or whatever. But hammer it tight and drop it into the molten aluminium in the pot while it melts - submersed - and I manage to get away with some useful billets for machining. I don't cast parts in moulds... failed miserably when I tried a flywheel in Mazak.
Interesting thread finding out all the things I do that are wrong.
Thanks guys.
K2

How many times did you try?

 

[master53yoda]

I think I'll pop in here,
I process automotive power train parts into ingots for the Hobbest and ship allover the US I have shipped some outside of the US but the shipping triples the price. I have processed 30,000 lbs in the last 5 years shipped i 40 lb boxes. I started my foundry when i retired.
The aluminum from this scrap source is very close to A356,the silicon level is between 6 and 8 %, I limit the amount of pistons as there make up is higher in silicon, that doesn't mean that pistons are not good source for casting it just that I try to maintain the consistency as close as I can.
The biggest difference between casting grade aluminum and most extruded or other, has to do with the surface tension and the metals ability to flow into thin areas of a casting. If the casting is over .25" most any material can be cast. As far as machining goes I use a mist on the cutting tools and have no problems with machining. With all my shipments I include recipies for dross and gass removal flux as well as a heat treating process.

Art b

 

[timo_gross]

I prefer to sell my scrap at 20 Ct and buy new material. I never can remember the pricing, but not worth to think about "home brew" bar stock.
Easy said: I can buy 6061 T6 in small quantities locally.

A couple of questions which will reveal both my interest and my ignorance on this topic:

1) Would the machining properties of these various ingots be improved by "tempering"? I confess that I don't actually know what that term means with respect to aluminum, but I'm aware that some grades of aluminum are miserable to machine when untempered, but well behaved when tempered ... or something like that.

2) Is it possible to add silicon or other alloying ingredients to the melt to improve the properties? I have seen videos with cast iron where the caster adds ferro-silicon (? or something like that) to improve properties.

Doing proper heat treatment of Aluminium is not really easy for the home shop. Material must be held at right temperature for very long time and then quenched quickly. It is easy get it wrong "Hardened" Aluminum machines much nicer than soft state, one reason I always buy new bar stock.

To make Aluminium Castings I would cut up some old car parts that are machined from castings. (wheels, pump housings etc.)
It might be not too difficult to figure out a fair deal with the recycler. Swap one type of scrap with another.

 

[Steamchick]

Richard, I have made about a half dozen billets of aluminium from scrap in ny 3in High crucible, poured into a plot steel tube to make a bar for a screwdriver handle or something equally "low engineered".
One or 2 have just been remelted as wrong in various ways. But my Mazak piece is on a running model engine. It was a casting for a cylinder end cap with combined cross head guide. I used a plaster mould.
K2

 

[Richard Hed]

Richard, I have made about a half dozen billets of aluminium from scrap in ny 3in High crucible, poured into a plot steel tube to make a bar for a screwdriver handle or something equally "low engineered".
One or 2 have just been remelted as wrong in various ways. But my Mazak piece is on a running model engine. It was a casting for a cylinder end cap with combined cross head guide. I used a plaster mould.
K2

Why not keep trying? It sounds to me like you didn't give it enough tries.

 

[ddmckee54]

Steamchick:

What happened when you used the plaster mold, did the casting fail or was that one a success?

Don

 

[Steamchick]

Hi Don, plaster mould with MAZAK worked well second time.
Richard, I shall continue, but try and learn from experts to shorten the time to "consistent results". What I have learned amongst other things,
# the alloy for deep drawn aluminium cans is lacking the silicon used for castings. So probably OK for big, unstressed lumps, like tool handles! If it casts without inclusions ....
# Wrought aluminium isn't right either.
# scrap sand-casting material may be quite good - but may be lower in silicon than original alloy. Die casting scrap is not right.
Good to learn from the experts!
K2