North State

My First Attempt (Picture Heavy)

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Well, having always had a desire to learn metalworking (See my post in the intro section to get my story.), and being frustrated with the progress I was making, then throwing out all of my accumulated parts for my original plan, I stared over. I settled on this propane burner set up. Thanks to whomever credit belongs.

I made one slight modification, though. I found trouble with getting the flame to hold her own with that 3/4 nipple on the end. So i deleted it. I will most likely grind out the threads on the flame end reducer to enhance the flame by reducing any turbulence. 

I got a 10 gallon air tank off a compressor that was flooded in hurricane Florence, from my local junk man. I used scrap pipe for the burner guides which I tapped and added 3/8" bolts to hold the burner(s) in place. Not knowing how much heat one burner would produce, I planned for a second burner. After I cut off the ends, I again used scrap 1/8" plate for the openings. I used some 2" square tubing scrap to make the hinges and some 1/4" flat bar for the latch. Luckily, I work at a boiler plant and we had some contractors doing some refractory work inside our fireboxes. I was able to get some left over Harbison Walker (Greencast I believe)refractory and 2" Inswool blanket. I used the refractory on the body and the Inswool on the doors to reduce weight when opened. While I havent had the chance to run her through the paces, I am fairly pleased with the results thus far. I have some light weight 15" fire brick that I plan on cutting a belly in and use to make the forge floor.

Please let me know what you think. Your most wise and holy counsel is appreciated!

Following are pictures along the way. hopefully they will load in some form of chronological order.

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Is that a solid cast refractory inside?  Is it one of the expensive and insulative refractories or just a common cast refractory?

If it is a full wall thickness of common cast refractory then that forge is double plus ungood! it will take hours to come up to welding temps and burn large amounts of propane doing so.   Unless you are using it commercially and running it 24/7  solid non insulating refractories are NOT what you want for the walls.  2" kaowool with a thin coating of refractory would work much better.

Perhaps you may want to read through the gas forges 101 thread  and not make the same mistakes as others basing their work on youtube yahoos.

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11 hours ago, ThomasPowers said:

Is that a solid cast refractory inside?  Is it one of the expensive and insulative refractories or just a common

Thanks for the advice, ThomasPowers. I admit i am a greenhorn, but the technical data on the stuff I have says it is rated for 2500° F. Being new to the forge universe, I can't confirm or deny this. The only YouTube advice I have used is on the burner, which i took with a grain of salt when I had to modify it.

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And nothing I mentioned had anything to do with the temperature rating!  I was interested in how much heat transmission it has and how much heat (BTUs) it takes to come to working temperature; both should have a BTU somewhere in the equation and both have a factor in how much fuel you have to pay for before you can even start heating a piece.

When you insulate a house do you worry about the temperature rating of the insulation?  No you worry about the R rating.

Commercially they generally are concerned with the ruggedness of the inner layers as they plan to run them for long periods and don't want to shutdown for a reline very often.  We are generally concerned with the cost efficiency of heating the system and it's tolerance for heating and cooling cycles.  (I've seen industrial systems that had *1* heating and cooling cycle per reline while my home forge may have 4 a weekend!)

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...and nothing I mentioned had anything to do with being an educated on heat transmission, expansion and calculation. When I find a formula I will try to see if my set up is satisfactory. In the mean time, here is the tech data from my refractory.

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So what you needed is the "Insulating Castable" line.

Off taking another load to the house; back in a day of two.

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23 minutes ago, North State said:

nothing I mentioned had anything to do with being an educated on heat transmission, expansion and calculation.

You seem to be focused on whether the material can handle the temperature in the forge.  That is important, but it's not the only thing.  Some propane forges can exceed 2500 degrees F by the way, but it should be ok.

What Thomas is pointing out is that using only a non-insulating refractory for your forge will cost you a lot of money in fuel (and probably time) in the long run.  In general the more mass you have to bring up to temperature the more time it will take and the more fuel you will burn.  So, even if that material can handle the heat, you will be waiting longer before you can begin forging and you will be spending far more on fuel than other options.  You may need more burners than is normally estimated to bring it to heat and keep it at the temperature you want as well - which of course also means more fuel burned.

Ultimately it's your forge, time, and money to do with as you like. We just tend to point out issues that people who are beginning may not have considered yet.  We've made a lot of the mistakes already.  We're hoping that the newcomers can learn from our old mistakes and come up with some new mistakes that we can learn from.

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You may be ok there though.  After looking at the specs, it has lower density and thermal conductivity than Kastolite 30, which is a product we normally recommend as floor and wall "armor" for a forge chamber.  However, the recommendation is normally to use a half inch or less layer of Kastolite over 2 inches of ceramic fiber blanket for insulating purposes.  I've never made a forge using only castable refractory, so I don't know how that compares to the construction method using a couple inches of blanket with a relatively thin layer of refractory on it.  I do know that a thicker layer of the refractory I've used does indeed take longer to heat up than a thinner layer.  I strongly suspect that your forge will take a lot of fuel to operate.

As a side note, if you plan to do any forge welding be aware that silica based materials are far more susceptible to destruction by flux than alumina based materials.  That is true whether it's castable refractory, fiber blanket, insulating firebricks, or pretty much any other material.  The refractory you've used is about 40% silicates and about 45% alumina, so I would expect it to be somewhat resistant to flux, but not impervious.

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Genuinely, thanks for the helpful advice. I know that that the sages of IFI consider not taking their advice as anathema, but be assured, the mistakes that I may have made were comitted before I found IFI. Alas, since i have made it this far, I guess I will give it a whirl as is and see what kind of heat retention I get. Since the variable in question is the type of refractory I used, we will just have to see. I have been looking for a formula for calculating forge efficiency, but have come up dry. Is there a sticky for that? I know the area of my forge, so if u can find the formula, I can plug in the specs from my refractory info and everything else. Thanks again for the help.

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Since you've already cast the lining I wouldn't suggest anything different.  If it seems like you're going through fuel too quickly then you may want to consider building a different forge in the future.  On the upside, this one will help you determine what you like and don't like about your current configuration so the next one can be even more suitable to your needs.

There are too many variables to calculate forge efficiency with any real expectation of accuracy. Construction materials, forge chamber shape, and exhaust openings probably play the biggest roles here, but there are other factors as well.  I roughly estimate my forge's efficiency in units of hours per BBQ size propane tank.  However, even that is variable depending on several factors, such as size of the stock I'm working (I change my exhaust openings accordingly) and whether I'm doing general forging or forge welding.

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Buzzkill, thanks for the encouragement. Thomaspowers had me thinking my forge was jacked when he didn't know exactly what I had, but in his defence, nor do I totally. Being a noob is tough sometimes. Since the refractory in the boilers at work is designed to keep the heat inside the firebox, and thus enhance efficiency, my logic said it should do fine. We will see. Who knows, if I have to eat crow, I guess I could just it out and start over as per IFI instructions! Standby for function test!

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ALCON,

Just a little update on the forge progress. As discussed before, she hasn't been proven yet. Its been a fairly busy summer around here. Anyway as far as construction, here's what went down this past weekend...

...added some stainless expanded metal to the doors. We will see if it holds up to the heat.

...oh and I made a stand for the DIY Anvil stand too. I know its top heavy. I'm going to beef the base up later.

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Before you fire it up make sure you cover the ceramic wool with a refractory such as Satanite, maybe you could coat it with the refractory you have already been using. When the wool gets up to temp it will release fibers that are pretty nasty to breath in, you definitely want to avoid that. With only hard refractory that forge is going to have trouble heating up without using tons of fuel. If its not efficient I would look into using that ceramic wool for the interior. Regardless I am excited to see it burning!

-Mark

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Thanks for the advice, Marcus. I am afraid of the refractory issue. Its going to be some nasty chipping if i have to  to start over. I had her built before I found the forum so here goes. I will put some on the doors as per your recomendation.

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If you rebuild it two 1/2 inch layers of ceramic fiber insulation, 1/2 inch of castable refractory, and a layer of IR reflective coating and it will be much more efficient. You do know about hydrophilic colloidal silica mixed with water sprayed on the kaowool or whatever fiber blanket you use to keep the inhalation hazard of ceramic fibers at a minimum? Good luck and let us know how it goes.

Pnut

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I thought there was some spray out there that would stiffen up the surfce of the wool. My question is this, suppose I been out the hard refractory and put in the wool, how tough will the refractory e with the softer wool behind it? Will it want to collapse? That ws my concern from the beginning before I stumbled upon iforgeiron...

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Posted (edited)

I don't use a gas forge but before I built the charcoal forge I was planning on building a propane forge. The rigidizer is just hydrophilic colloidal silica mixed with water and a little blue food coloring so you can see where you sprayed it. If I remember correctly you can use a couple of thinner layers of castable instead of one thick heavy one. Have you read the consolidated notes on forge building? Everything you need to know about lining a forge shell is in it. Good luck and keep us posted.

Pnut

Edited by pnut

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The rigidizer will help keep the wool in one spot and to some degree the harmful particles in. What I do is first I spray the wool with rigidizer (you buy the stuff online or make your own) and let it dry in the sun. Once it is cured I spritz on some water and add the refractory coating. The water helps let the refractory stick to the surface of the wool, and is especially important if you are using Kast-O-Lite as if the wool is dry it will suck the water right out of the Kast-O-Lite which is a water setting mix. Regardless, I would recommend you use Satanite and apply it in multiple small coatings until you have reached a good 1/4". After each layer let it dry in the sun or use a small light bulb to heat the inside. Once that is all said and done finish curing the coating with increasing heats in with the forge. The Satinite does tend to crack so make sure you have some more handy to do repair jobs. I would be careful with that mesh over your wool if you do apply a refractory coating. The expansion of the mesh as it is heated may crack the refractory.

-Mark

 

Gas Forge Refractories and Supplies

 

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1 hour ago, Marcus_Aurelius said:

What I do is first I spray the wool with rigidizer (you buy the stuff online or make your own) and let it dry in the sun.

A better option is to spritz with water, then spray on the rigidizer, let dry, and then bring it up to temperature with the forge or with a torch of some variety. If it's hot enough, it will start to glow. The water wets the fibers of the wool allowing the rigidizer to coat them evenly, and then the firing turns the rigidizer and the fibers of the wool into a cohesive mass. 

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Punt,I read it, however I was already 75-80% underway before I found it. Reluctantly, I will most likely be doing some chipping and relining. I just hate having to back up, but I think it will be worth it to re do the lining. Marcus and JHCC, i will definitely take your thoughts into consideration. Thanks!

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I understand, going backwards is no fun, but in the long run I think you will actually save time and money by relining your forge.  It will heat up much quicker so you won't be spending $ on heating up your forge it will be spent on heating up metal. If you follow the directions in the post I referred to and you read you will have a forge that is efficient enough to weld. A well lined forge can also make up for slight inefficiencies in your burner. It's a proven process and you should have a good forge if you line it per the instructions in "my consolidated notes for new forge builders" By Loul.  I know you said you hate going backwards, we all do but going backwards to get good results beats going forward with something you don't really want or that isn't going to do what you need it to. Don't get discouraged you have the hardest part done and that's building a decent burner. Lining your forge isn't much more difficult than fixing a hole In drywall or plastering some lathe. 

Pnut

 

 

 

 

 

 

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Well said, Pnut. Thanks for the encouragement! I actually found the burner to be quite easy! From the looks of it, it has a consistent flame and I am optimistic about it. We will see. Wonder how hard of a time that castible is going to give me as I chip it out?

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After I last posted, I felt a surge of ambition, so I went out and chipped out the castible. It wasnt as difficult as I anticipated. I had some 2" Insawool on hand so I carefully sliced it into an aproximately 1" layer. I sprayed 3M super 77 glue inside to hold the wool and now I am reseraching rigidizers. Pnut, I looked into what you called "hydrophobic colloidal silica" turns out they sell the stuf at West Marine near me. The only thing is, I cant find much information on using it for this application. It is definitely the nore cost effective option. Real wool rigidizer on amazon runs north of $30 while the thing of silica is only $15 and I could get it right away. Alas, I dont want to be in the same boat I was a few days ago, tearing out and re-doing...

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As for after I get the wool rigidized, does anyone know how I can apply the castible without looking like i fingerpainted the Mona Lisa? I was really proud of how clean the refractory looked on my first go round. It was a bit of a PITA, getting it to go around my support pins, and I think that in so doing, I mixed it too thin. I hesitate to hand paint the casitble inside because I want it to be as smooth as possible, but if it just cant be done, someone please let me know.

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Reread the post. It said hydrophilic colloidal silica. How did you get the hydrophobic silica to mix with water?  You're planning on putting a castable refractory over it still aren't you?

Pnut

I replied to a notificationvia email. I see your second post. You are going to use a castable. Did you read the consolidated notes for new forge builders thread? It will explain buttering the inswool so that the refractory will stick to it. 

Glad you're making progress.

Pnut

Edited by pnut

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