New Welding Forge WIP

With the forge curing nicely, I figured I'd better get busy and build the lid. I cut off a 3" tall section of the same diameter pipe that I used for the forge body...... Split it, and then filled in the sides/gaps with 1/4 plywood to make it match the outside diameter of the forge. Laid the form on a piece of plywood, and used nails to ensure everything stays put. I decided to build the lid just the reverse of the forge.....putting kawool on the inside, and making the rest out of castable.

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The pieces of bent rebar will be handles for the lid....inset into the castable.

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Next I mixed up some castable to a very soupy consistency, and basically soaked the kawool in it. Then I laid the kawook in the form, and mixed up a thicker batch of castable.....

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Then it was just a matter of filling the form with castable, and putting the rebar in place......

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I got the castable way more wet then I wanted to......but I guess it is what it is. Now it's just a matter to curing time before I can do anything else. Once I get it in place and fired, I'll update the thread with how it works out.
 
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Thought I would add to this thread and show you what I use for a burner in my welding forge. Before we get to that, I just want to mention something that I feel if VERY important with any burner you use in a forge......KEEP IT SIMPLE! I've spent countless hours of time trying to help folks with forge burner problems, and I've come to fully believe..... The more you overtake the pluming, the easier it is to stop up the drain. The vast majority of problems I've assisted with/solved concerning forge burners can all be directly related to over complicated burner designs. Just keep it straight forward and simple......and your life will be much nicer.

I choose to use a very simple, single burner with a blower on my welding forge. Easy to build, very few things to go wrong, and it just plain works.

It all starts with choosing the correct blower for the application. While I know that many folks use "squirrel cage" blowers, otherwise know as Shaded Pole blowers, that are very inexpensive, and easy to find, I personally think that is one of the least desirable blowers that a person can choose. Squirrel Cage/Shaded Pole blowers are NOT designed to function with ANY amount of back pressure....something that is always present in a forge burner application. Here's what happens: As back pressure increases, air flow decreases, and causes the motor to heat up, and burn out the windings. Don't get me wrong, some folks who use their forges very little, have gotten away with using this type of blower for years, but for those who do any kind of higher volume or prolonged usage of their forge(s), they can be a real pain. I know, because I did just that.....used shaded pole blowers. They worked fine, as long as I didn't run the forge much, but as I got into longer and longer days at the forge, blowers started burning out. At the time I simply didn't know any better, so I just kept replacing them....and kept burning them out.

Finally I broke down and purchased a blower that is specifically designed for forges. At the time (over a dozen years ago) I believe I paid $125 for this one...

Welding_Forgebunerandblower2.jpg


It's 164 CFM, and has been going strong for all these years. If you're going to use a blower on a forge, I highly recommend this one/type.

Here's a pic of the entire burner I use in my welding forge:

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From the blower to the forge, the parts are:
-164 CFM electric blower, wired into a ceiling fan speed controller (DO NOT use a typical light dimmer, it will cause the motor winding to burn out....you've been warned!)
-Pipe Flange with 2" threaded fitting
-2" X 12" piece of blade iron pipe, threaded both ends
-2" X 1 1/2" 90 degree elbow (this is a very important part of the burner....the reduction from 2" to 1 1/2" aids greatly in the fuel/air mixing, and increases velocity at the burner end for better control and high temps)
blowerburner4.jpg


-1 1/2" X 18" black iron pipe. (this is the pipe that goes into the forge and is the "burner"

Propane is delivered through a common rubber propane hose, controlled with a propane needle valve. (there is also a ball/shut-off valve located at the propane regulator). I far prefer a needle valve to a ball valve at this location. Its far more controllable, and makes fine adjustments MUCH easier. The 2" pipe has been drilled and tapped to accept the 1/4" pipe nipple. The nut you see next to the burner pipe is to "snug" the pipe nipple in place. I DO NOT USE ANY TYPE OF ORIFICE IN THE PIPE NIPPLE. I tried several differ sizes of orifice, and found that with the needle valve, they were totally unnecessary, and made the forge much more difficult to "tune".

blowerburner3.jpg


After a bit of experimenting with this burner, I installed 3" concentric pipes in the burner end..... I found that it quiets the roar of the burner nicely, and it gives me a better flame pattern, with a wider adjustability then without the concentric pipes.
blowerburner5.jpg


Finally, the burner holder is an important part of the equation too. You want something solid and heavy gauge, that will be able to withstand the high/long endurance heat. It need to be welded solidly to the forge body, and be of the proper ID so an to "fit" the burner you're using. In my case I used a pice of schedule 80 pipe, and using a boring bar, enlarged the size to about .030" larger then the O.D. of my burner pipe size. This allows for expansion of the burner pipe, but isn't so oversized that it allows flames to come out the burner holder. I drilled and tapped three 1/2-13 holes approx 120 degrees apart, and use 1/2-13 bolts to hold the burner in place.

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The new forge had been curing for a couple of weeks now. I'm guessing that in about another week it might be cured enough to do some test firings and see how things are going to work. The currently plan is that once the castable refractory is cured enough, give it a good cleaning with a brass brush, blow it out, and apply ITC-100.

Once I get it ready, I'll add to this thread as things move along.
 
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Over the past week I have been slowly firing the new welding forge.....starting out below 1000F several times, shutting it down and allowing it to cool. Day by day I inched up the temps to 1200F, 1400F, then 1600F.....letting it cool down fully after each firing. Today I decided that for better or worse, I would see what it would do. Any time you build a new forge, that differs as much as this one did from my previous welding forge, there is always some doubt about how it will perform.......those thoughts are now long gone! :)


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After starting the forge and letting it idle for about an hour, I inched the temp upward a bit at a time, and at about 1950F the steam started rolling, water was dripping off the front and back openings, and out of the burner holder. I just about shut it all down......JUST ABOUT..... but took a chance and kept going. The temp stalled for a while right around 2100F, but I suspect it was due to all the steaming/dripping going on. The forge ran, holding at around 2100F for about an hour. As the steam dwindled, the temp started rising again, and before I knew it, the temp was 2430F!


After a sigh of relief, now knowing that this forge is going to reach the level of heat I was hoping for, I tweaked the fuel and the blower a bit, and it just kept climbing. I honestly do not know where "top end" is on this forge...... my pyrometer tops out at 2499F..... and there have been times that I check the temp readout and nothing but a row of "EEEE" shows.....telling me the forge temp has topped 2500F!

And this was WITHOUT any coatings on the interior! I'm going to pull the forge off the table this week, and give a coat of ITC-100, and that should make it even better! :)

The forge actually got to 2490F, and I figured I'd better not press my luck. So I dialed it back a bit, and used it to forge down some 410SS that in the future will become laminated with Mosaic.

So, now you know everything about how I built this type of welding forge and burner. If it works for me, there's no reason it shouldn't work for you too!
 
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At 2445° I think that I would start worrying about my thermocouple holding up. No doubt that you'll be able to weld in it.

Doug
 
Hey Ed, That forge looks great, and it was cool seeing the process done with castable. It should hold up for a long time. Quick question though, what psi were you running on your propane reg at welding temp? Also is that pipe next to the door a additional blower to keep down "dragons breath"?
 
Doug: Wrecking the thermocouple is certainly a concern. The ones I use in the welding forge are rated for 2440F...... but experience has taught me that the rating put on a thermocouple is generally 500-600F below where the will actually be damaged. Several years ago I asked some questions to the tech folks at Omega, and they told me that all the ratings listed on their thermocouples are 500-600F BELOW the point where the heat will damage them..... I'm not so sure about other outfits, so that's the main reason I've stuck with thermocouples from Omega, and why I generally recommend purchasing from them versus other sources.


CMS3900: For comparison, the old welding forge ran at 5 psi. This one has a larger volume, so I had to bump up the pressure to about 6.5 psi. I expect that once all the moisture is driven out/its well cured, I'll start and run it at that psi until it gets to temp, then be able to back off the psi to maintain the heat. It's got about 5-6X the thermal mass that the old forge had, so I expected it would require more fuel, but the other side of that coin is that the increased thermal mass SHOULD allow it to hold heat much better then the Kawool forge, and allow me to dial the fuel back once that mass it up to heat.

You're absolutely correct on the pipe next to the door. It's a rectangle piece of tubing, with a 1/8" slot milled down the edge facing the door, and its connected to a blower that I scrounged off an old Caterpillar paver. Nothing more the an air curtain. I guess it's worth mentioning that without the air curtain, about 2' is as close as I can get to the door without getting singed. :)
 
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Thanks for the detailed build info and pics! I was wondering if you could provide more detail on the 3" concentric pipes in the burner. Just eyeballing , it looks like about a 1 inch and 3/8 inch pipe with 1/4 inch spacers inside of the 1 1/2" burner pipe?
 
There's no "one size fits all" with the concentric pipes. The key to them is to get at least 2 smaller diameter pipes inside the burner pipe, at least 3" in length. The spacers on the burner in the picture are 1/4" keystock.....but I did have to taper a couple of them and tap them into place with an hammer. Then they are MIG welding just on the outboard end to hold in place. Probably the most critical part is where to place the burner when inserting it into the forge..... for the castable forge I keep the end about 1/2" from the ID for the forge chamber.....if you stick that end with the MIG weld on it too far into the forge, it will erode the welds/burn the end of the pipes off. You'll know when/if that happens......because when the concentric pipes fall out, the burner will sound like an F16 jet engine! :)
 
Thanks! I plan to build at some point soon and debating blown vs aspirated, this seems like a very straight forward, design.
 
If you ever plan on making damascus, I highly encourage building a blower type forge. You can always dial it back/down for general forge work. If you go with a venturi burner(s), there's only so much heat you'll be able to get out of it/them....and they will almost always be less fuel efficient then a blown burner. I can't over emphasis how valuable keeping a forge design simple and clean can be. I've spend far too many hours on the phone or typing emails trying to help folks with overly complicated forge designs.... I don't know where some folks get the idea that the more "bells-n-whistles" they put on a forge, the "better" it's going to be......usually just the opposite is true. :)
 
Thanks for putting this together Ed! That's an interesting tip about the 3 concentric pipes with the burner! I try to remember that!
 
Just an update...... the new forge is now in place, and being used. Beyond the fact that this one takes a bit of time to come to welding temp (which I expected, but still have to get used to) it's working great, and I'm hoping it will hold up for much longer then the old kawool welding forge. I'll wait, and use it for several months before I declare the design to be a "success", but right now it appears that's what it will be. :)
 
45 min to an hour to 2350F.....give or take based on the conditions. The old kawool welding forge only took 15-20 mins to reach that temp. On the upside, when I put one of my monster billets in it (8"x1 1/2" X 40-50 layers) it doesn't take near the recovery time that the kawool for did. As with just about everything in Bladesmithing/knifemaking, its just another trade-off. :)
 
Not really..... I have a 500 gallon tank for the forging shop..... historically it only requires a fill about once every 14-16 months. In that time frame I go through approx. $400-$500 worth of propane.
 
Nice build Ed. Even though the castable is expensive compared to time lost I imagine it will pay for itself in short order. It makes me restless to have my shop down.

Regards, Fred
 
I'm slowly getting the pics updated to my new hosting...... stupid photobucket! I get there eventually.
 
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