Author Topic: Smelting  (Read 7730 times)

Offline Darren

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Smelting
« on: July 16, 2009, 12:08:30 PM »
Just got back from my local scrappy (he's collecting my mill on Saturday.... :ddb: :ddb: :ddb:)

We were discussing metal for the shop and he doesn't really get anything in that would be suitable for our needs.
But....he did suggest smelting alloy into ingots and such. I can have all the scrap bits and bobs of alloy inc car wheels and cylinder heads, gearboxes etc I could ever need.
I can't say I'd wish to get into smelting, but then again that's a lot of alloy scrap he was showing me today...

Years ago when I was really poor I remember melting mixed metals down on our coal fire to extract the alloy to weigh in.....I did say I was poor, not much better now ... :lol:

Does anyone here smelt, is it worth the aggro, how hard can it be ???????

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Offline Andy

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Re: Smelting
« Reply #1 on: July 16, 2009, 12:39:05 PM »
Those sound like big lumps of metal and would need a fair bit of cutting up to get them into the typical 'back yard foundry' crucible. Also need to consider the cost of gas or other fuel which would be used.

I'd say that the idea could be a goer if you can overcome the above, although the resulting new alloy that you end up with might have unexpected properties.

Andy
« Last Edit: July 16, 2009, 12:42:33 PM by Andy »
From probably the smallest, dampest and most untidy workshop in Bradford, West Yorks, England, if not the world..

bogstandard

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Re: Smelting
« Reply #2 on: July 16, 2009, 01:19:09 PM »
Darren,

As Andy says, you will end up with a real junky metal. Even the local scrap processor, who recycles ali, mainly for the automotive industry, has to be very careful what goes into the mix. Most of their labour force is into separating the different types of ali, and even then, they mix pure raw additives to it to get it something like.
I have worked with the raw material of a general mix as you are suggesting, and I will tell you now, it is not nice. Imagine trying to machine solidified evostik, it sticks to your cutter and sort of tears from the surface rather than cuts. I had a friend who used to work in a foundry casting steel mill rolls, and I asked him to melt some ali bits down and cast it into bars for me. I have tried all sorts of silly things in my time, that one turned out to be one of the silliest.

But to get back to your other thing about smelting. Melting the stuff.

When I do a steam rally in September, there is usually a chap next to me who casts and makes his own full scale engines, not large ones, say up to 18" tall. Resurrecting old industrial engines from the past, say for use in small farm dairies etc., of which there are no more examples, working mainly from original drawings and photos.

He does all his casting the old way, before furnaces etc. During the winter he does his melt on the open fire in the house, and in the summer he digs a pit in his garden for doing the same thing. He mentioned that once he has got things up to heat, things were no different to a normal furnace, he would just keep adding his ali scrap, and taking out what he needed for the pour. He told me his most prized possession was a large stainless steel vessel that he uses for his smelting. I think it must be something like the deep pans they use in a canteen servery.
He was also saying that he uses the old techniques for casting, no specialised oiled sand etc, he uses very finely riddled dry earth. It seems to work, as his engines look very nice and always attract a good following.

John

Offline Bernd

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Re: Smelting
« Reply #3 on: July 16, 2009, 02:17:04 PM »
Darren,

All you can read about metal melting in the backyard: http://www.backyardmetalcasting.com/index.html

Bernd
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Offline Darren

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Re: Smelting
« Reply #4 on: July 16, 2009, 04:32:39 PM »
Umm a whole new arena.....  :scratch:

I've read a couple of times that car engine alloy makes good machining ingots/castings.

But coke cans and pie trays do not. Machine wise they are sticky but do cast well with a shiny finish.
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Offline John Hill

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Re: Smelting
« Reply #5 on: July 16, 2009, 04:56:22 PM »
....aaaahhhhh!  Memories! :D

As a schoolboy some of us friends got together and built a furnace in a backyard.  We went to the brick works and got the right clay to build up a suitable fireplace and someone at the brickworks made us some flower pots without holes in the bottom.

We used coal which we found in a big pile by the rail yards. ::)

The first lighting went really well and was blown by someone's mother's nice new horizontal vacuum cleaner, the aluminium truck pistons melted in what seemed to be no time at all and using big tongs we poured the molten metal into a box made of 3x2, wood!  ****

Then we got worried about what would happen if  the vacuum cleaner got dirty or anything so we extended the pipe and put the vacuum cleaner up out of harm's way on the roof of the garden shed.

The second burn went well too but for some reason which I forget we stopped before it was all melted, then when my friend restarted the vacuum cleaner there was a sickening boom from the roof of the garden shed and not much of the vacuum cleaner could be found.

Obviously when we stopped coal gas had risen up the hose into the cleaner and was ignited by the motor brush sparks.

***The wooden moulds was someone's idea and was claimed to be common in glass making, the molten metal chars the wood and from then on you have a carbon lined wooden mould! 
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Offline Darren

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Re: Smelting
« Reply #6 on: July 16, 2009, 05:00:46 PM »
Those sound like big lumps of metal and would need a fair bit of cutting up to get them into the typical 'back yard foundry' crucible.


Just get one of these.... :ddb: :ddb: :ddb:

http://www.youtube.com/watch?v=9JUBBEhrvfc&NR=1
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Offline Andy

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Re: Smelting
« Reply #7 on: July 16, 2009, 07:03:47 PM »
That is one scary machine  :bugeye:
From probably the smallest, dampest and most untidy workshop in Bradford, West Yorks, England, if not the world..

Offline Darren

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Re: Smelting
« Reply #8 on: July 16, 2009, 07:10:05 PM »
You wouldn't want to fall in would you....

Bit more reading and I see that alloy melts at around 600deg, there was me thinking it was more like 1,200 for some reason?

Having read a little bit and watched a few Utubes it doesn't seem to be that hard to achieve? People are making lathe and other machine castings at home and they seem to be doing OK?

More reading required...... :)
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Offline Darren

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Re: Smelting
« Reply #9 on: July 16, 2009, 07:19:10 PM »
What I have not yet found out is what to do with dirty alloy, ie with bits of steel in it.

I assume you knock the easy stuff off before melting, what happens to the rest. Does it just sink to the bottom of the crucible?
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Offline John Hill

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Re: Smelting
« Reply #10 on: July 16, 2009, 07:31:40 PM »
If I recall correctly the school metal shop teacher had a piece of hooked fencing wire which he used to pick out the gudgeon pins from the melting pistons.

He also had a flux of some kind, it looked like a handful of crystals, which he threw into the pot then scooped off a layer of grunge that floated to the top.

(I am talking about the school shop here, not the backyard job with Mum's unfortunate vacuume cleaner.)

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Offline Darren

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Re: Smelting
« Reply #11 on: July 16, 2009, 07:35:53 PM »
Thanks John,

I saw someone throwing something in the melted mix and then scooping the crud out but he didn't say what it was....
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Offline John Stevenson

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Re: Smelting
« Reply #12 on: July 16, 2009, 07:38:00 PM »
It needs to be as clean as possible, i.e. studs removed etc and once mented you throw in some ge-gassing tablets which boils it up to release any impurities in the metal which then floats on top as dross.

This is skimmed off and a flux applied to the surface whilst the final temperature is reached, then this is skimmed off just prior to the pour.
Alloy wants to skin and oxidise very easily so the cleaner you can keep the metal the better.

Final quality is a bit of a question brought about by what the original material was and other factors.

Just because the parent metal was good quality doesn't meant to say that the new part will be the same as some components can burn off in the remelt.

John S.
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Offline Bernd

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Re: Smelting
« Reply #13 on: July 16, 2009, 09:47:11 PM »
The stuff is boarax. It's a flux to help make the impurities float to the top so you can skime them off.

Bernd
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Offline Darren

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Re: Smelting
« Reply #14 on: July 17, 2009, 08:02:51 AM »
Thanks Guys, all interesting stuff.

The main reason for looking at this idea is because dirty scrap no longer fetches enough reward for the scrap dealers to haul about. So it's mounting up in the yards.
Being offered all "you can carry" is certainly an incentive.

I don't think "doing it" presents too much of an issue, Initially I'd think about chucking bits in the cast stove during the winter to separate the steel.
But the question of the final quality still remains.

Only one way to find out I guess..... :smart:
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Offline John Hill

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Re: Smelting
« Reply #15 on: July 17, 2009, 04:56:50 PM »
Darren, I expect any diecast bits you have will be better metal that cans and cheap sheet material.  I save old floppy and hard disk castings and the scrappy is real keen to sort those from the rest.
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Offline Darren

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Re: Smelting
« Reply #16 on: July 17, 2009, 05:22:36 PM »
Funny you should say that John as I was stripping some dead hard drives down just the other week and kept all the cases.... :thumbup:
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Offline PTsideshow

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Re: Smelting
« Reply #17 on: July 26, 2009, 10:52:23 AM »
The hard drive casting are a real good grade of alloy. The problem with cans is two fold really, one both sides are coated with an epoxy plastic coating the inside with BHP to protect the contents from picking up the metallic taste or the Ph assorted food item from reacting from the metal. The outside of the cans has an ink receptive coating layer, then the multiple passes of ink colors, then a clear protective layer to protect the printing.

Then we can add into the mix all the crap that gets stuffed in the inside the cans before they are scraped. Not to mention all the remaining wet and dried contents. Plus the fact that the thinness of the metal some goes up in smoke, and the repeated adding of material to the melt to make up for the air space. Unless you have a large capacity crucible it is fuel and time/work foolish.

Pistons are generally a good grade of metal, engine blocks and heads next, tranny cases and others are a mix of all most anything and therefore should be avoided if possible. Not even taking into account the oil all over them.

One of the better safety issues is clean and dry, will prevent the steam and other liquids converting to steam when least expecting, during the melt. And flinging molten metal globs in all directions.

As far as some of the disingenuous internet video's and sites that are giving info be careful, as they put out some bad if not genuine information. As with the video's of things that aren't what them seem. Faking it with editing, or saying one thing and then doing something else. Abounds on the net.

Most of the die cast can be of any alloy that the caster has at the moment. As when it started out it was zinc die casting, or zinc casting. Some of the brass dust catchers from India at the local flea market have some much iron in it it is magnetic. Much to the dismay of the Indian/Pak guy that has the stand, when I walk by with my magnet. As he is BSing somebody about his family foundries "high standards of purity for their brass castings". :lol: :lol:
 
Here is the start of some of the best books on metal casting furnace, crucibles making etc in the bookshelf section of the forum.
http://madmodder.net/index.php?topic=84.0 they are on pages 9 and 10 starting with this one.
http://madmodder.net/index.php?topic=111.0 more than you might ever want to know about forges,furnaces and kilns.

Any of the books by C.W.Ammen are as current today as when they were written for the basics.

Lindsay publications are also good.
glen
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glen

Offline Darren

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Re: Smelting
« Reply #18 on: July 27, 2009, 04:19:45 AM »
Thanks for your insight on this subject Glen,

Have you done any casting yourself?
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