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Having problems heating metal


Cannon Cocker

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Hello all.  This is my first post.  Let me say that I am very glad that I came across this post today.  I recently built my own forge with ideas I got from watching videos on Youtube.  The inside dimensions of my forge are 12" wide 8" tall and 24" long.  I have a large door/opening on the front (12" X 8") that I block off with a brick and the back is 6" X 8" with a swinging door.  All sides of the forge filled with 2" of refractory cement.  I am confident that this forge will hold heat well.  My problem is with the burners.  I have 3 burners but am only able to run one at a time with limited success.  If I try to run 2 I have to choke one WAY down to keep them from blowing themselves out, and even then they "chug" really bad.  It takes about 15-20 minutes on my first heat to get any kind of color in 1/2" round in order to start forging.  I started with a 1/16" orifice and switched to a much smaller one, about .035".  I have also tried adjusting the height on my nozzles inside of the 3/4 X 1 1/4 bell reducer.  The pipe on the burners are 3/4" nipples that are 10" long.  They protrude about a half inch under the refractory straight down from the top.  Does anyone have any ideas of how I could get them to heat better?  I'll try to get some pictures posted on here.  

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A number of things, pics would be a huge help in diagnosing. Video would be even better. That is a large space, and refractory cement is definitely NOT the way to go for saving heat. Thermawool, ridgidizer, then seal it and a refractory coat on the other hand...I dunno, I don't play with propane much anymore, used to play with it mostly for casting. Someone will chime in. A big space with poor refractory will take a significant amount of preheating before starting work.

Not really sure of your design, but three at a time may have a very large draw and be freezing your supply.  What kind of regulator is it? What pressure are ya running? Is it naturally aspirated, or forced air? Pics, and someone better than propane than me will help get ya fixed up.

Also, with that avatar name...13B?

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12 minutes ago, Nobody Special said:

Also, with that avatar name...13B?

Close!  I was an 0811 That's artillery in the Marine Corps.  I'll go out and take a video and some pictures now.  I'm sure that will give others a better idea of what I'm working with.  Thanks!

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Using the rule of thumb of one 3/4 inch diameter burner per 350 cubic inches you'd need 6 to 7 burners to bring that beast up to welding heat.  I hope that's insulating castable refractory and not actually refractory cement.  Either way you have a LOT of mass to bring up to temperature before you can start forging.  It will be much worse if it's refractory cement though and it probably won't last long since that material is not designed to be a hot face directly exposed to flames and it's usually not insulating.

How is your propane supplied to the burners?  100 gallon tank, BBQ tank, etc.   Do you have an adjustable regulator with a pressure gauge installed?

The ends of your burners should actually be up inside the lining, not protruding down into the forge past the lining.  However, that's more to protect the ends from burning up quickly rather than causing a huge change in burner performance usually.

Just for a point of reference for you, my latest forge is a half cylinder (or D shape) that is 9 inches wide by 4 inches tall by about 9 inches long.  With a single 1/2 inch diameter tube naturally aspirated ribbon burner I'm at a good orange forging temperature in less than 10 minutes.  I'm not sure what you will be doing that would require that large of a forge, but nothing I've ever done (including some blades over 24 inches long) would require anything like that size of forge.  I can tell you for sure I would not want to foot the bill for the propane to run it.

Since I've never personally made or used a multiple burner forge I'll leave the diagnosis of those issues to someone else.

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The real gurus should be along soon enough.  I’m going to go ahead and guess that you have back pressure causing the burners to chug like that.  It’s an awful huge space to heat but without a way for the pressure to escape it will force itself back up your mixing tubes on your burners.  My advice would be to build a wall out of Brick or refractory that you can place in the forge to shrink its size.  Then use one burner and see how it does.

You are going to hear a lot about how it is foolhardy to trust most YouTube “Blacksmiths”.  Since joining IFI I have realized how much bad information is being shared there.  There is a lot of good stuff too, but it is hard to know the difference without having the base of knowledge you can get here.

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Welcome aboard Cannon Cocker, glad to have you. If you'll put your general location in the header you might be surprised how many of the gang are within visiting distance.

You've fallen into the same mistake so many of us have with early forges, that's WAY too large. Unless you're going to be forging crank shaft size stock a little more than 1/3 the volume is plenty. Whoever's Youtube videos you followed to build it put that builder on your list of NEVER DO IT HIS WAY! list.

There are a number of established forge plans in Iforge's "Forges 101" thread. In "Burners 101" we discuss burners a LOT. 

The basic ratio of one each WELL TUNED 3/4" burner will bring 300-350 cu/in to welding heat is a good rule of thumb but the burners must be built and tuned properly. The max length of your mixing tubes should be about 6". The bell reducer should be IIRC 3/4" x 2" and run a 0.030 dia. Jet. Bear in mind I'm not a linear type burner guy but some rules of thumb hold true anyway.

I developed the T burner for reasons I've gone into a number of times before and won't bore you now. Regardless I can make an educated assessment. With only a 1 1/4" intake, 0.035" jet and a 10" long mixing tube it can't burn efficiently, it MUST urn very rich so choking is exactly the opposite of what it will require to burn reasonably well. I've laid out your basic ratio in the preceding paragraph.

Starting from the shell (the steel or whatever on the outside of the forge chamber) and going in to the open chamber that is in contact with the flame. Two layers of 1", 8 lb. refractory blanket. Rigidized layer by layer as you assemble it. First because rigidizing makes the blanket more durable. Secondly and long term healthier it encapsulates the ceramic fibers that make up the insulating blanket and can be a breathing hazard. Rigidize refractory blanket, okay? The next step is applying 1/2" of a 3,000 f., water setting, high alumina, hard refractory for the flame face. Once set and cured the hard refractory is armor for the insulating layer that will resist mechanical damage and chemical erosion if you weld in it. Lastly is a good kiln wash. This is a high temp refractory that seals and provides a final layer of protection that is proof against hot welding flux and increases the IR re radiation of the forge liner.

With variations that's all there is to it. Regardless of what you see on the internet. We spend a lot of effort undoing the poor . . . stuff presented as good design on the web. It's not you, nobody is born knowing this stuff and it's easy to get sucked in till we have some knowledge and experience under our belts. 

Do a little reading in the Forges 101 and Burners 101 sections till you get a handle on these things and get back to us. We'll be around and like helping new addicts get hopelessly hooked on the craft.

Frosty The Lucky.

 

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I was given a boatload of Vesuvius monolithic refractory from a friend that rebuilds power plants so that's what got put in it. The tank in using now is a BBQ tank, but I just acquired 2 100# tanks, just need to get them tested and filled. 

Frosty, I take it that you are suggesting building a new forge from scratch. In your opinion is there any way that I could save this forge? Such as restructuring the inside with the materials you listed to reduce volume, or do you think that would cost just about as much as building a new one or off a tank or something. (finances are awfully tight) 

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Set it aside for now. If you ever need to forge crankshaft-sized material, you'll be ready to go. If you find that you need to cannibalize some of it for another project, you'll be ready to go. In the mean time, it will be lurking in the corner of your vision as a reminder not to get too far ahead of yourself.

I'm not one of the gas-forge-building guys, but if you still have some of that Vesuvius refractory, one of them can tell you whether or not it will be appropriate for the hard layer of your next forge.

Regarding tight finances, there are plenty of ways to cut your costs. Talk to an HVAC contractor about scraps of ceramic wool. Rigidizer is cheap. You already have (hopefully) usable refractory. Be of good cheer; all will be well.

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Note you don't want the burner flames impinging directly on the stock!  

Many people when they build a large forge intend to make swords. Unfortunately they hadn't researched enough to know that you only want to heat the workpiece as long as you can work it before it cools---say about 6"  heating the steel outside of the work area degrades it due to decarburization, scale losses and grain growth.  

We also see a lot of people saying that they used a non-insulative refractory to save money.  I have trouble with folks saying they are saving money by spending many times more for propane than a proper insulative refractory will cost. (I don't know the specifics of the one you are using and so don't know if it counts as insulative or noninsulative...)

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3 hours ago, Cannon Cocker said:

I was given a boatload of Vesuvius monolithic refractory from a friend that rebuilds power plants so that's what got put in it. The tank in using now is a BBQ tank, but I just acquired 2 100# tanks, just need to get them tested and filled. 

Is the refractory you were given Ceram 45?  If it is that should be able to handle the rigors of an interior lining for a forge fairly well.  However, it is only slightly more than half as insulating as Kastolite 30, one of our recommended castable refractories.

So, were I in your shoes with that refractory for free, I'd still use it, BUT I'd go with at least 2 one inch layers of 8 lb. density ceramic fiber blanket between the shell and the refractory lining.  Of course I'd also shrink the internal volume significantly.  As mentioned it would probably be easier to start over and go smaller than to modify the one you built.

A BBQ size propane tank will almost certainly have problems keeping up with 3 or more 3/4 inch diameter burners.  It will need to pull so much so quickly that it may be more than can even pass through the regulator you have.  Even if it does, your tank would likely cool rapidly to the point where you could experience a pressure drop within a fairly short period of time - or the tank outlet might even frost up on you.  The two 100 lb tanks linked together should do the trick if you're going to stay with that many burners of that size.  One might even cut it.

As mentioned, grab some snacks, a cool beverage, and a comfy chair then peruse Forges 101 and Burners 101 on the forum.  It's a lot to wade through and some parts get rather technically involved.  However, once you make it out the other end you should have a much better idea as to what makes efficient, long-lasting forges and burners.

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43 minutes ago, ThomasPowers said:

I don't know the specifics of the one you are using and so don't know if it counts as insulative or noninsulative...

I'm not real sure about that either. However I do know that this type of refractory is what they use in the burning chambers of power plants. So I assumed it would hold in the heat well. But you know what they say about assumptions! 

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Big power plants run 24/7 and are typically insulated (sort of) by soft brick outer layers. The refractory in the furnace chamber is typically thick, heavy uninsulating especially in oil furnaces/boilers Burning oil is even more chemically active than propane so it erodes liners. Another reason they have such a high thermal mass is in case they need to shut it down briefly, it won't cool off quickly and fall apart.

I'd put that forge on a shelf and build a small single burner one to start out with. Check with your friend and see if they use ceramic blanket, if so they'll be filling several dumpsters a week with what they rip out and trimmings of what they replace it with. That's where I get my Kaowool, a local HVAC service and supply company. I can hardly stop by to buy something without leaving with a car full of trash bags of Kaowool trimmings. Building codes prohibit use of cut pieces (trimmings) when servicing furnaces, etc. it all has to come off a roll. That leaves lots of useful size trimmins for likable scroungers. :)

Frosty The Lucky.

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I'm sorry I thought you were trying to build a hobby forge and not a powerplant.  The use cases for powerplant materials may not overlap the ones for a small efficient forge.

If we were totally worried about using a forge liner that would resist the heat I would think tungsten would make a dandy liner.  However we are more looking for something that will hold the heat *in* and then coat the wear surface with something that is mechanically stronger yet still can deal with the heat.

So please stop going on about it being used for powerplants unless you have decided to build a powerplant.

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I was just reading something earlier today about someone who bought a large welder from a military surplus depot, planning to use it for all manner of projects. It was big, right? And military, right? It just had to be perfect for everything!

Well, when he finally got a copy of the manual, it turned out that it wasn’t appropriate for anything much thicker than a beer can. Lesson learned. 

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I've just gone through the whole learning curve of propane forge building. If you want it hot and efficient, you have to use what these guys are telling you to use.

The problem with using other materials is that they either don't insulate well, or disintegrate after moderate use (I know, I've tried).

A small combustion area with a good burner, well insulated, with good materials, will give you a nice hot forge. 

When you're just starting out you only need to heat small pieces of metal. Plus, you only want to heat a small section.

I'm cutting 4 inches off a forge I just built because it's too long. It heats up too much material. 

I think a small propane tank is a good size. I would also suggest setting your burner at a tangent to the radius of the inner chamber to create a swirl. A swirl gets the chamber really hot. 

I would also suggest a blown burner, but that might be more than you can afford right now. Mikey and Frosty burners seem to work quite well and should be fine. 

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On ‎7‎/‎13‎/‎2018 at 5:35 AM, Cannon Cocker said:

In your opinion is there any way that I could save this forge? Such as restructuring the inside with the materials you listed to reduce volume, or do you think that would cost just about as much as building a new one or off a tank or something. (finances are awfully tight) 

The first thing you need to do is to rebuild the burners. mount 3" to 3/4" reducers, to find out what the 'forge will do with decent burners; then lets talk about everything else.

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21 hours ago, Mikey98118 said:

The first thing you need to do is to rebuild the burners. mount 3" to 3/4" reducers, to find out what the 'forge will do with decent burners; then lets talk about everything else.

Would I be better off putting the larger bell reducers on or should I go ahead and buy T's to transform my burners into Frosty's design?  Or are you suggesting the 3 X 3/4 reducers because of the large amount of volume in my forge?  I had planned on cutting 4" off of my pipes and rethreading them to get down to the "rule of 8". 

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On 7/14/2018 at 5:21 PM, Mikey98118 said:

In your opinion is there any way that I could save this forge? Such as restructuring the inside with the materials you listed to reduce volume, or do you think that would cost just about as much as building a new one or off a tank or something. (finances are awfully tight) 

I think that you would save money and get a better forge by just starting over.

Let me know if I can help you.  xxxxxxxxxxxxxxxxxxxxxxxxxxxx

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Tonight I cut off 4" from one of my burner tubes to make it 6" long just to see how much that changed the way the burner acted.  It went MUCH better!  However because of the immense volume of my forge it was still taking a while to heat the steel. (1/4 X 1 1/4 flat stock).  So I broke some chunks off of a cinder block I had laying around and put those on either side of my stock.  After only a few minutes of warming up it became what I would call decently efficient.  I was able to start drawing out my material (I'm making a pair of tongs) with each heat only taking a minute or two.  So here's what I'm thinking.  If I dome the walls and top of the forge using Kaowool and castable refractory bringing the width of my forge down to 6" inches and the height to an average of 7 that will give me aprox 336 cu/in per burner.  Then my thought is in order to NOT have to run all three burners all the time I will make a "sliding wall" out of insulation materials that I can move down to give me access to my second burner or take out to use all three (probably only for heat treating operations).  This plan makes sense to me but I want to hear some of your opinions about it as well.  

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