Aluminum forge body?

S

syvmn

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Apr 5, 2009
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Hey guys. I'm in the process of building a forge and was wondering what you thought about this aluminum tank I found. It is 12" diameter and about 20" deep. I'm not intending to build a large forge so I was thinking of a 3" layer of kaowool all around making a chamber about 6" diameter. I probably wont need the full 20" depth either so I might shorten it up to 16" or so.

Are there any issues with using aluminum as the forge body?

P1000804.jpg



This is the burner I made (EZ burner). I don't have a pressure gauge yet so I really don't know what pressure I'm running it at but it seems to make a nice flame.

[video=youtube;cqLVkvojeVk]http://www.youtube.com/watch?v=cqLVkvojeVk[/video]

Any thoughts on chamber size would be appreciated.
 
I find a 4-6" chamber is just right. The aluminum should not be a problem if the forge is well insulated as you plan.

Consider making it a poured refractory liner that is wrapped with K-wool to fit the aluminum tank.
Use a 4" cardboard tube and an 8" piece of PVC pipe as the mold. Make the liner about 12-14" long.Drill/cut holes through the two for a piece of PVC that is the size of your burner flare. Position it so the burner will just enter the chamber at a tangent. Put the PVC piece through the tubes and use some sealant if needed to close up any sloppy fitting holes. Place on a piece of plywood and use construction adhesive to cement the tubes to the board. Pour the liner mold with Mizzou or some similar hight temp refractory and let cure for three days. When the liner is cured, tear out the cardboard and cut the PCV with a skill saw set to just barely cut the tube on both sides. It should then split off easily with a few cuts from a box cutter. Paint the inside of the liner with ITC-100, and wrap it in wool until it snugly fits the tank. It should be easy to make a hole for the burner in the tank to line up with the one in the liner.
Use insuboard to make ends that snugly fit the liner and the tank. Cement them in place with satanite.
Add some legs or make a cradle and you are done.
 
Hopefully I followed what you said. Is this the end product you were thinking? I'm not sure if I should do a 4" or 6" opening. If I do a 6" opening and 15" long that gives me 423 cubic inches. I think I saw somewhere about how many cubic inches you should expect out of one of the EZ burners.

forge.jpg
 
Not to hijack your thread but are you planning a blower? I'm going to be building a forge similar to yours with a 5 gallon metal bucket or I might use two and cut one in half so I can make a smaller opening without stacking bricks to close it up. Could you have your air blowing in a pipe with the burner pipe inside of it so you only have one hole going into the forge ?
 
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I'm not planning on using any blower at all. The only time you would use a blower is to feed air to the burner. I don't think you would ever just use a blower by itself shooting cold air into the forge. Or maybe I misread what you wrote.

The burner I'm using doesn't need a blower though.
 
syvmn said:
Hopefully I followed what you said. Is this the end product you were thinking? I'm not sure if I should do a 4" or 6" opening. If I do a 6" opening and 15" long that gives me 423 cubic inches. I think I saw somewhere about how many cubic inches you should expect out of one of the EZ burners.

forge.jpg
Click to expand...

I'm pretty sure the kaowool goes between the metal skin and the refractory liner. ITC-100 seals the refractory.
 
Yes, the refractory liner is wrapped in K-wool on the outside.
If you use a 4" inner chamber, and 2" walls that makes the liner 8" wide. Wrap that in 2" thick K-wool and it should fit a 12" shell nicely. The ITC-100 is a coating on the inside of the poured liner.

With an atmospheric burner, a 2" poured liner is possibly overkill. I would suggest making a blown burner if you plan on using the forge for HT and general forging. You can make it PID controlled and punch in any temperature you want the forge to hold at.
 
The only thing it will be used for at the moment is heat treating. To start off I will only be doing stock removal until I am comfortable and proficient at that part of the game.

My concern with a 4" chamber is that I'm going to have a huge hot spot at the point where the burner enters the forge. Any thoughts on creating an environment with even heat?
 
If the burner enters at a tangent to the interior of the forge the flame will swirl around the outer part of the interior. This evenly distributes the heat. You don't want the flame aimed directly at to work.

Wayne
 
insanity said:
If the burner enters at a tangent to the interior of the forge the flame will swirl around the outer part of the interior. This evenly distributes the heat. You don't want the flame aimed directly at to work.
Wayne
Click to expand...

Kind of like this, left side. If you were to have it upright, the flame would spiral upwards, laying down, spiral out towards the front opening

furnace.jpg
 
The main purpose of a poured refractory liner is to make an even heating chamber. It will have a hot spot at first, and take as much as fifteen to twenty minutes to fully soak the refractory, but once up to heat, it will stay at a very even temperature. Placing a blade in after it is soaked will allow a very even and controlled HT. PID control will make it even more accurate.

My concern for your plan is that you want to make a HT oven but are planning on using a forging type burner.
Make the burner a blown type and add the PID control. A blown burner is easier than a venturi burner to build anyway. Take as look at my plans posted in the stickies for a two-stage PID controlled forge. Those who have built one claim less than five degrees fluctuation.
 
Aluminum has a very low melting temperature compared to steel, 1220 degrees F. That's lower than the operating temperatures of a forge. I hope the insulation is up to the task. Is that aluminum tank going to hold up?
 
The outer shell on a forge might get up to 500-600F at most. On many it never gets past 200-300.
I agree that the shell is the least concern as to cost in building a forge. It can be just a wrap of 24 gauge steel with sheet metal screws holding it together. Many poured refractory forges , and most HT ovens have just such a outer shell.
 
So here's the conclusion I have come to.

1. 3" Kaowool, 1" refractory, Coating of ITC 100....giving me a 4" diameter
2. 14" long should give me all the depth I need for now
3. I'm going to stick with my venturi burner to keep costs down
4. I'll get a PID/thermocouple but just for monitoring purposes. At this point I'm not going to go the extra mile for full control

forge2.jpg


I do have an 8" SS tube I could use but that only lets me use 1" Kaowool and 1" Refractory cement...or 2" kaowool with just a coating of the cement. Hmm...

The 1" of refractory vs 2" is because I'm not making mass quantities of knives, nor am I going to be hammering anything. I think the time it would take to heat up 2" would actually cost me more in fuel even though its more efficient once its up to temp. I just don't see myself running the forge for an hour at a time.

What do you think?
 
Please post pics as you build if you could I'd be very interested in seeing how you build it and how you built your burner.
 
Here's a few pics of the pieces to my burner. The design is Ron Reil's. Here's a link to his website (which I find ridiculously hard to navigate...): http://ronreil.abana.org/sitemap.html
Look for the "Reil" or "EZ" burner design plans. The only place where I deviated from his design is the flare at the end. Since I don't have any way to flare a 1" x 3" pipe I just used a 1" x 2.5" and put a 1" to 1.25" bell reducer on the end. In the video above you can see that it seems to work quite well. I have never build a burner before and have never been in another blade smith's shop so I really have nothing to compare it to.

Venturi.jpg


Venturi2.jpg


When I get around to building the forge I'll start a WIP. I keep changing my mind about how I'm going to go about doing it. I wish I had a 10" tube so I could do 2" Kaowool and 1" refractory cement....oh well.
 
That plan should work fine. The aluminum shell should barely get warm.

The venturi burner you made will do the job, but I think the bell reducer flare is not right. Try just a sleeve of 1" stainless pipe without the reducer. That should allow the flame to mix and expand as it leaves the burner tube. The stainless flare will last longer.

When running the forge, let it heat up slowly. Running the burner wide open into a cold chamber invites cracking the liner. Once heated to above 1000, you can crank up the heat to whatever yo want. Allow the chamber to fully soak before doing a HT.
 
I tried the burner without the flare and it doesn't work. I haven't researched it enough to know why, but it seems venturi burners require it. Ron suggests flaring a 1" piece to 1-1/4" on the end or you can buy a SS one from him. I'm cheap...

Here's the burner without the flare. When I start to turn up the pressure it blows itself out

[video=youtube;umfa1PE4r4s]http://www.youtube.com/watch?v=umfa1PE4r4s[/video]

Here's the burner with the flare. When I turn up the pressure it sounds like a jet taking off :o)

[video=youtube;pw2YTtwADEA]http://www.youtube.com/watch?v=pw2YTtwADEA[/video]
 
That type of burner will burn outside the forge with a flared end but the flare is not needed in the forge just a straight pipe.

Richard
 
Huh, good to know Richard. I will be very interest to see how it works when I get that far. I'm still trying to source as much of the material I need locally. Half to save on shipping and half to support local shop owners.
 
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