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? on heat distribution (propane forge)


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I made my forge from a freon tank (pic posted earlier). I tried to forge weld yesterday. I know it gets hot enough as I was melting steel. The problem is it gets hotter in front of the burner hole into the tank. Has anyone had this issue and is there maybe an idea or two to get around this issue? I think I may try taking a corner piece of firebrick and setting it in front of the gas input to deflect a little and see if it works. Any ideas?
Thanks
RD

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It's common for single burner forges to have a hot spot in front of the burner. Some people bring the burner in on a tangent to create a swirling action and distribute the heat better. But most seem to just go ahead and use them with the hot spot. I'm not sure I understand why you can't weld in it as-is. If you're melting steel, you're definitely getting it hot enough to weld. What exactly is the problem?

With that said, I do have a few questions about your forge. First, it looks like it's lined with castable refractory alone -- no wool of any kind. Second, it looks like there's no hole in the back to pass long work through. Am I correct about both of those observations? Third, are you using some kind of door on the front?

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I melt steel and have a hard time welding. The problem seems to be scale (solved by lots of flux) or having the bar get too soft in a spot I am not trying to weld!

In my efforts I have found that using a piece of ceramic wool to cover the hot spot and the bar goes under the insulation The area to be welded is not insulated. OR Making sure that the hot spot is NOT used for welding, since the material seems to scale worse in that location. I can put small stock on either side of the hot spot in my forge.

I have only been successful with faggot welding (in any type of forge), so find a big grain of rock salt for this advice.

I accidentally broke the brick floor to my forge and there was a thin layer of metal under a thick layer of scale from my accidental meltings.

Phil

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Phil,

You bring up an important point and that is the generation of scale by any heat source. My converted Sandia forge will also melt steel but I can't weld in it unless I dump more fuel than necessary with the needle valve and have excess burning in air. It's also been known for centuries that a hollow fire in a coal or charcoal forge won't weld either so the user should look for scale generation as a prime root cause for weld failure.

I'm not sure if many people "forge" weld with an OA torch but I stumbled on it some years ago in my shop while trying to weld some small stock together and noticed that an excess fuel flame with about a 3x feather worked every time if I used flux. An OA torch gets plenty hot enough (since that's what we used before stick came along) and forge welding two pieces on the anvil should be no different. I played around with the torch knobs and it was pretty easy to see that the fuel content of the flame was important to weld success - the same is true of propane inside an insulated box.

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I did not make a pass thru on the back. My next one will have a pass thru, and will be bigger. There is koa wool and its coated with itc 100. I use fire bricks at the front for a makeshift door. As far as the problem..... I'm a newbee. I have yet to weld by myself. I'm working on it and hopefully will figure it out in the near future. Just have hot spot issues. I worked on finishing a knife today so didn't fire up the mini dragon. Will continue and may try the wool to see if that works Phil.
Thanks

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One of the reasons for the tangential burners is to direct it away from the work and allow time for complete combustion. Right in the flame is the worst place to heat a piece of steel. It's full of super-heated oxygen, unburned fuel and all kind of nasties that screw up welding.

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One of the keys for me is to make sure the entire interior of forge is hot before putting anything in it. Even with good burner design/placement creating a swirling flame, metal is going to heat unevenly. Blades are a prime example - even a forge with perfect heat distribution will heat the thin edge faster than the spine and the tip faster than the base. You just need to move the piece around to get even heat distribution - you can't expect the forge to compensate for the varying thichness of the metal.

My forges have removeable rear covers, one with a slot for passing thin stock such as blades through. The rear covers/caps help hold the heat in and even it out.

I spent an inordinate amount of time designing and build a forge to create a swirl effect and more even heat - still had to move the metal arould to compensate for thickness variance:

Two propane forges - both heat uneven metal unevenly:
NewForgeBurnerDesign3small.jpgMyVenturiForge11small.jpg

Rear Covers:
1 BackCover.jpg

BackCover-1.jpg

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