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Silent Matt

My homemade forge

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I just finished up my budget propane forge build. The body is an 11" long chunk of 8" I.D. pipe that I found in the weld shop of the community college. The end caps are 1/4" steel (only because my buddy was cutting some 1/4" plate on the plasma table at the time). The fittings are from a local plumbing and electrics store and the home depot, I think I have about $40 into the hose and pipe fittings. I used 12" long 3/4" pipe with 1 1/4" to 3/4" reducers for the bells and 1/8" steel pipe for the orifice tubes. I drilled the orifice holes to .046" which might have been a little large.

 

I was going to line it was ceramic blanket but my buddy had a 50# bucket of refractory patch that I could have. Figured I give it a try, if it didn't work I'd only be out the time I spent packing it in.

 

The flame is an even blue, is this what is should be? I think maybe I have too much burner per area... It shoots a foot long blue flame out the front.

 

I think it might be better with horizontally mounted burner tubes and a shut off valve for the rear burner. I can post a list of fittings used if anyone wants it.

 

Now on to the roller mill ;)

 

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This is about as low as it will reliably idle.

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This is about 3/4 turn open.

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And the patch I used as refractory. I gave it about a week but it was still soft to the touch and I'm impatient... It steamed off a lot but got hard as rock where it contacted flame.

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Nice :)

 

Does the Pro-patch insulate at all?

Those two burners might be overkill for the volume of your forge though. I think that the general rule of thumb is one per 350 cubic inches of forge volume. The interior of my forge is just under 700 cubic inches, and I have two side-arm burners. Someone who has more experience than me hopefully will weigh in.

I would also suggest that if you use this to heat treat, that you use a muffle to prevent hot spots from the direct contact of the flame. I use a four inch square tube when heat treating.

 

Nice build though :)

Edited by Wes Detrick

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Thanks guys. As far as the Pro-patch, I'm not sure how much it insulates, I've only ran it for a couple minutes so far. I think I'll put a valve on the rear burner so I can just run one for small stuff. Thanks for the tip on heat treating, I'll definitely use it.

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Looks like you have more burner than space to burn in to me also Matt and that will send a lot of flame out the door.

after you drive out the moisture with test fires give it a good long burn and let us know how hot the outer suface gets.

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I'm not familiar with that patch material (phos bonded is bad, and 70% would be HORRIBLE, when dealing with liquid steel as the phos will leech out into the steel) but generally they tend to be adequate insulators and many will not ever cure at room temp and must be fired.

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Is there a way that you could rotate the body of that forge 90° to the right? With the flame hitting right on the bottom of the floor you are going to run into some hot spots, which are not good for heat treating, and possibly pitting of your work. I know that if you go online and look at commercially made gas forges they all seem to have the flame aimed right at the floor of the forge but this is not good for knifemaking. I don't know about the chemical makeup of the refractory that you used but that much mass will take a bit to come up to forging heat. I have a smaller forge that was cast from a bubble alumina castable refractory and it's a bit slow in heating up but when it gets going it's a fire belching little beast.

 

Doug

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Jerrod, I didn't know about the phosphorus (is that what the "phos" is?) leaching into the steel. Is this something that happens due to contact or a gaseous exchange?

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Yeah, phos=phosphorous. Gets a little tiresome to say the whole thing when you talk about it a lot. Likewise moly=molybdenum. Anyways, I wouldn't worry about it in your case as you won't be getting hot enough to dissolve the refractory into your metal (this is the problem when melting steel). If you do get any phos pick-up via diffusion it will be so small that scale and grinding will remove it all. Wellons' website says it is their proprietary blend, but not much more than that. In wood drying kilns the phos in the refractory won't matter at all. The worst offenders we ever allow in the foundry have 3.6% P2O5. I would guess from the name that yours has more than that, but probably not too much more. The 70 probably refers to the amount of the main refractory, most likely alumina or silica, or the grit size thereof. In the future though I would recommend putting it over a layer or 2 of insulating blanket to reduce the thermal mass. This works quite well. Also, adding water to it to thin it out is generally not a problem. Heat it pretty slowly to dry (even without thinning it) otherwise you may get cracking/spalling. Again, I have no experience with this product, but I do with several others and this is a general rule of thumb based on those.

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Thanks for the info. I think I might put a coat of ITC-100 or something similar on the inside to help keep the heat in.

 

 

 

 

 

Update- I blocked off the rear burner and added an air mattress blower to the front one, it gets much hotter, much faster now.

I ran it for a 15-20 minute forging session and it gets a little too hot to touch on the outside.

Edited by Silent Matt

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Nice build. The forge will only get hotter on the outside the longer you keep it running. That refractory patch might have been great as a skim-coat over some kaowool or inswool batt insulation, but as a stand-alone insulator it won't do very well. Basically, it's slowing down the heat transfer to the outside simply because its density. I would definitely coat it with an IR reflector like ITC100 or Metrikote.

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