Metal casting furnace details

[Graziano]

Here's a link to a small workshop metal casting furnace complete with drawing and details. This actual furnace dates from the 1950's and has been in continuous use since then, through two owners. It uses gas via a red pottery kiln gas regulator and air via a high pressure, low volume 1 hp motor centrifugal blower (large 20 inch diameter by 3 inch wide). This is a fast furnace that takes minutes to melt a crucible full of aluminium and so avoids hydrogen porosity and the need for inocculants to prevent this.

I thought I'd post this info for anyone interested in metal casting, though I can seriously state that learning first hand from an experienced metal caster is well worth while to avoid injury. You can avoid little problems like hot metal explosions caused by not preheating your scrap metal or a moist sand mould, or porosity by casting in humidity over 70% (I've seen barometers in a small foundry for this purpose).

Astro-Tel - Gas Fired Furnace (http://www.turbofast.com.au/astrotel/furnace1.html)


Cheers,
Mark

Furnace melting a load of Bronze:
http://www.woodworkforums.com/attachment.php?attachmentid=144225&stc=1&d=1281351352

Resin bonded silica sand, 1/2 a mould:
http://www.woodworkforums.com/attachment.php?attachmentid=144226&stc=1&d=1281351352


Resin bonded silica sand, 2/2 a mould:
http://www.woodworkforums.com/attachment.php?attachmentid=144227&stc=1&d=1281351352

Cast bronze out of the sand mould:
http://www.woodworkforums.com/attachment.php?attachmentid=144228&stc=1&d=1281351352

Cast bronze after passivation and machining:
http://www.woodworkforums.com/attachment.php?attachmentid=144229&stc=1&d=1281351352

[eskimo]

here it all is in PDF format
fig 1 & 3 are the same going by the links on each of the pages...the same sketch pops up
I need to read it properly

[Graziano]

That's a good idea condensing it into one document. If there's any technical queries I can ask the current owner about them and pass it on. Laurie, the original owner whose website that is, is 87 or so and a bit crook these days so I wouldn't want to start an avalanche of email enquiries to him. Both owners tell stories of people coming in off the streets and asking about casting, then being shown that furnace, and after a pause the person refuses to believe metal casting is done with that furnace instead of a massive furnace and teams of people running around.

[Master Splinter]

If you are after furnace building and metal casting info I've found this site quite a good resource - http://www.backyardmetalcasting.com/

[Graziano]

If you are after furnace building and metal casting info I've found this site quite a good resource - melting metal in a home foundry, backyard metalcasting, metal casting (http://www.backyardmetalcasting.com/)


That's quite a good site, about the only thing I'd be wary about, are the flower pot clay crucibles and the steel crucibles: The clay ones as described in certain "Brothers" books are famous as being "suicidal" throughout the metal casting industry compared to a commercial $170 silicon carbide crucible . The homemade steel crucibles do dissolve iron into the molten aluminium in them and can cause alloy problems at molten aluminium temps.

Commercial carbide crucibles are cheap enough, will hold iron, bronze and aluminium (not at once of course) and you don't have to worry about them dropping their hot load all over the floor like a flower pot. The hot metal will make large scabs of cement explode off the floor when spilt from steam formation in the cement. :oo:

[19brendan81]

Thanks for the link. I have been casting aluminium at home for a couple of years with charcoal and am ready to switch to gas for a cleaner burn. I did cast breifly with an oil fired furnace but it was slower than the charcoal and produced a pretty bad smell.

Whats the best place on the east coast to get silicon carbide crucibles? I have been meaning to get one for a while as my steel one burnt out recently.

Brendan

[Graziano]

Thanks for the link. I have been casting aluminium at home for a couple of years with charcoal and am ready to switch to gas for a cleaner burn. I did cast breifly with an oil fired furnace but it was slower than the charcoal and produced a pretty bad smell.

Whats the best place on the east coast to get silicon carbide crucibles? I have been meaning to get one for a while as my steel one burnt out recently.

Brendan

Foseco Australia (http://www.foseco.com.au/) , silicon carbide is supposed to be cast iron only but also works really well for non ferrous too. Gas consumption is high with that furnace you'll want something a lot bigger than a nine kilo cylinder or you'll get freezing condensation on the outside of the cylinder.

[19brendan81]

Freezing on the outside doesnt bother me so long as it keeps fluid on the inside so it can supply the burner.

How does this burner perform re time and gas consumption for aluminium?

[RayG]

Foseco Australia (http://www.foseco.com.au/) , silicon carbide is supposed to be cast iron only but also works really well for non ferrous too.....

Hi Graziano,

I compiled a list of Melbourne Foundry Suppliers a while back
http://www.woodworkforums.com/f65/melbourne-foundry-suppliers-100407/

Interesting, I have always been told silicon carbide is better for non-ferrous, and clay graphite for cast iron... Foseco have A4 Clay Graphite crucibles for $35.75

I use a normally aspirated burner, and while it's fine for bronze and Aluminium it just doesn't cut it for cast iron, last time I tried cast Iron it melted but not hot enough for casting. I need a blower.

I like the blower setup on that furnace, that's what I need for mine so I can do cast iron.

Thanks for posting.

Regards
Ray

[19brendan81]

Ray what sort of gas economy do you get melting alloy? And how long does it take?

[RayG]

Ray what sort of gas economy do you get melting alloy? And how long does it take?

Hi Brendan,

Here is the burner I am using.

http://www.backsaw.net/pics/burner.jpg

The cylinder is just a normal LPG cylinder, with a adjustable LPG regulator from BOC.

http://www.backsaw.net/pics/boc_reg.jpg

I can't help with gas consumption, I did try once to measure it with bathroom scales, but the scales kept auto powering off :) and re-zeroing when powered up.

As far as time goes, to melt 1kg of bronze takes about 7 minutes.

Regards
Ray

[19brendan81]

Looks the goods to me. Melting a keg of bronze in 7 mins is pretty good.

With consumption, are you getting multiple melts out of a cylinder? How many would you get? 5 or 10?

[Graziano]

Freezing on the outside doesnt bother me so long as it keeps fluid on the inside so it can supply the burner.

How does this burner perform re time and gas consumption for aluminium?


I'll find out the details of the gas regulator, I did find identical red units with the outside adjuster knob in pottery supply shops as it was too large for the barbecue gas shops.

You won't get liquid out of a normal gas cylinder unless it has a refilling tube fitted like the big cylinders at service stations or you turn the cylinder upside down which is illegal. This furnace runs fine on a 12.5 mm tube from the regulator with about 15 metres of 12.5 mm tube from the cylinder to the regulator.

It takes about 15 minutes to melt a full crucible of aluminium and I did hear somewhere along the line that it has a calculated efficiency of 3%. The owner pointed out that even though it's inefficient, it's cost effective as it doesn't waste his time, just gas which is cheaper.


Hi Graziano,

I compiled a list of Melbourne Foundry Suppliers a while back
http://www.woodworkforums.com/f65/melbourne-foundry-suppliers-100407/

Interesting, I have always been told silicon carbide is better for non-ferrous, and clay graphite for cast iron... Foseco have A4 Clay Graphite crucibles for $35.75

I use a normally aspirated burner, and while it's fine for bronze and Aluminium it just doesn't cut it for cast iron, last time I tried cast Iron it melted but not hot enough for casting. I need a blower.

I like the blower setup on that furnace, that's what I need for mine so I can do cast iron.

Thanks for posting.

Regards
Ray

Hi Ray, I may have the crucible type wrong, I was quoting from memory, but this guy did find he could use the wrong type and it either lasted longer or was cheaper/better value to use that type for non ferrous. I'll find out some brands, sizes and types of crucible he uses, I think it's an A20 but don't quote me on that.

I do know some Aussie crucible suppliers have been charging way over top dollar for the better brands of crucible and then substituting the cheap Indian crucibles that aren't nearly as good.

Edit: He's using a Morgan Super A20 size in silicon carbide which costs about $160-$170 from Foseco, the furnace will melt a full crucible of aluminium in 20 minutes from a cold start and a full crucible of bronze in 35 minutes from a cold start and 16 minutes after warming up if you stack the ingots on top first and pre heat them a bit. He also said the big so called secret is the higher air pressure/low volume of the centrifugal blower compared to a high volume low pressure blower like an airconditioner squirrel cage blower.

[DSEL74]

G'Day Guys.

I'm interested in casting a few parts for a 1974 motorbike I am working on. I can make the patterns no worries and have rammed up green sand moulds many years ago. However I am looking for someone who already has a furnace that would be interested in doing that actual casting.

I am not game enough to build my own furnace etc from ebooks.

I am located near Doncaster in Victoria. If you know someone who might be interested in helping me out it be much appreciated.

Cheers,

Dale
[email protected]