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AustroTom

Furnace to forge aluminum

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Hello All,

new to this forum and lovin' it!

 

I'm planning on fabricating a large driveway gate out of aluminum and was wondering what the best way would be to heat the aluminum at a steady temperature of 750-900 deg. F. I'm guessing right now that natural and propane gas usually burn at a higher temperature thus start sputtering when dialed down.

I have a large quantity of scrolls and leaves to forge so the constant watching of the aluminum is not an option. Steady temp is a must. Would an electronic oven make more sense than an open flame forge?

 

Any info greatly appreciated,

Thanks,

Thomas 

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I'm planning on fabricating a large driveway gate out of aluminum 

 

The words *large driveway gate* and aluminum caught my attention. Have you ever seen a large gate made from aluminum? Do you want to do this gate in one large pour or do it in sections? How you going to connect the sections? How much sag is engineered into the span of the gate? Is the aluminum strong enough to to be self supporting AND have enough left over strength to support a wind load and 6 to 10 of the neighbor kids using it as a swing? Aluminum is a sought after metal for junkers. How are you going to protect your investment from a chain and a pickup truck late at night?

 

How are you going to make a cope and drag larger than the gate? How are you going to handle several hundred pounds of molten metal before and during the pour?

 

Lots of questions, 

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Greetings Tom,

 

Glenn covered most of the questions that I would have ask ...   Finish ?   You see a lot of gates out there that are anodized or professionally treated..  Have you ever tried to forge a leaf from aluminum ?  Not so easy...  I suggest you post pictures and sizes of the material that you plan to use...  I always considered aluminum as THE OTHER METAL..

 

Forge on and make beautiful things

Jim

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Forge, as in not cast?

 

Started playing with a few small pieces this year, nothing so big as scrollwork. (on a coal forge) It takes a bit of practice to forge hot without melting or cracking, and depends on alloy. A few times I was even successful.....ish. :rolleyes:

 

You could anneal and forge cold, it goes a lot further than you'd think before you have to do it again. Watch it though, melts really easy, sometimes right under that apparantly solid oxide layer. (Think - squish! ow ow ow ow!!!!) Also moves ridiculously fast compared to a lot of steel, especially when hot.

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Greetings again Tom,

 

Your reply puts a whole new spin on my suggestions...    Fantastic work...    I always wanted to try building a contained forge out of fire brick and use electrodes like the ones in water heaters...   With some electronics and some simple on off temp control this might be an option..   Again Beautiful work...

 

Forge on and make beautiful things..

Jim

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I would think electric is a good way to go.  There are plans for an electric heat treat oven on a British bladesmiths website, that might be a good starting point.  A good pottery supply place should have the elements and maybe even a controller.  I would either shield the elements completely or make sure you put a shutoff relay attached to the door so it cuts the power when you open the door.  You don't want to electrocute yourself.

 

Another option would be to build a muffle furnace.  Your burners would operate in a chamber but your parts go into a chamber inside the burner chamber.

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Thank you.

That's what I was thinking of: a furnace heated with something like a water heater coil (though would prob. have to be hotter), and a thermostat to regulate the temperature. This way it doesn't matter when I pull the material out of the "oven".

problem is I have zero experience with any type of oven/furnace construction (water heater coils for instance would fail horrendously when not submerged in liquids, right?).

So I hope somebody could steer me in the right direction and might help with the design.

 

Thomas 

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Just thinking out loud, I'd expect it would be possible to use "Incoloy straight rod heating elements". They are basically the same as water heater elements, but can be specified for use in air instead. Watt density would need to be much lower than for water heating, but the incoloy elemets are supposedly good to 1600 degF surface temperature. You'd need to find suitable elements for the size of furnace and carefully work through the manufacturers' design calculations; best is to work out a ballpark design and use this to fill in their design spec sheet, letting them do the final calculations.

 

Control would almost certainly need to be with a thermocouple and PID controller; these are cheap (probably a lot cheaper than a thermostat able to cope with the temperatures involved) and give much more precise control.

 

Personally, I'd use the controller to switch the power via an SSR, rather than a contactor, for shorter output cycle time, but the element manufacturer can provide advice on this.

 

What size of workpiece are you intending to deal with in the forge? I assume you'll be forging sections and joining them together afterwards?

 

I've built half a dozen electric HT ovens broadly similar to Andy Gascoigne's plans on the British Blades site, including a sword-length one. I'd expect going electric to be heavy on power.

 

I suspect that the temperature could possibly be achieved with Propane, given a bit of thought and a good burner design, though I've not tried to get down that low myself. The lowest I have aimed for on my forge was a steady 750 degC (1382 degF) and that was relatively easy (it was a general-purpose forge intended to go from HT to welding temperatures and also reached 1413 degC (2575 degF). If it's not possible to get the flame temperature down low enough simply through good mixture control, I'd expect a radiant heating system, where the burners heat the roof of the forge and the radiated heat from the roof heats the workpiece, to be possible.

 

It seems like an interesting project. Some more details on the forge dimensions needed would be good.

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Thomas, For very large jobs while in Florida we sent the stock out for commercial annealing and cold worked for texture.

For scrolls and such requiring forging we heated with a propane/air torch and a pine paint stick. Clamp torch to table and light. pass aluminum in front of torch and do a count. Rub with pine stick. When the pine stick left a black smudge mark you forge.

After a few feet of stock you get a feel and go. Sure some are overheated and crumble, but not many.

I have forged 1/2 round to 2x2 square solid this way.

Use 6061 or 6060 for solids and 3003 for sheet...the local marine boat builder uses a 5000 alloy...not sure which.

 

Often you need to cold forge to work harden some areas or use a network of supports to keep in good as it lacks the strength or iron.

 

I am sure there is a local NOMMA shop you can talk to...if not then call Art or Phil at Art's Work in Florida or Jack Klahm of Klahm and Son's

 

I was just out in California (LA and Oakland) if I had known I could have stopped in and showed you a few techniques.

 

Ric

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what would be wrong with a gasforge turned low , i can turn mine right down , and to see if aluminium is at forge temperature ,take a piece of pinewood and scrape it like you would write with chalk and if it leaves a charcoal like mark its ready to forge, cheers HJP

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