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Update on first (failed) San Mai billet


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I figured I’d start a new topic on my San Mai update so I wouldn’t be getting too off topic on the Show and Tell thread. 
 

So I decided to weld together a San Mai billet of 15N20 and 1084. This would’ve been my first full sized billet as it was almost as long as I wanted the finished blade to be. I was planning on forge welding the billet and stock removing from there just to see if I kept the core centered and successfully welded the billet. I’ve only tried small stacks maybe two or three inches until now. 
 

Unfortunately, my forge didn’t make the cut. I didn’t foresee having issues because it’s worked for everything I’ve needed up until now. But all I’ve used it for is heat treating my stock removal blades. So I’ve never needed to get a full billet to forge welding temps, and I don’t think it can do it. 
 

All this forge is, is a bunch of carved out fire brick sandwiched between some landscaping type bricks. It’s 18” long and about 8” wide. You can use those dimensions to estimate the carved out dimensions. But after having some sputtering issues with my burner, I tried to carve the opening to be a bit larger, and these bricks are crumbling and barely being held together, so I’m assuming there’s A LOT of heat escaping. 
 

I also couldn’t get the billet to heat evenly. While one part was heating up, another part would be cooling down. 
 

So anyway, I think I’ll need to invest in a two-burner forge before I give this a go again. I’m buying a 2x72 next week so I’ll just invest in a proper forge with that. But it would probably be a lot cheaper to build one... hmm.. 

 

So with all of this, can I still use the stack I’ve welded up and heated once I buy or build a new forge? I did bang on it a few times but not much. I’m hoping that if I can get it to forge welding temps I can just pick up where I left off? 

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That's the kind of burner I have :)

 

I could not weld with just one, even after fixing the other issues with my home-made forge, which included

 

- Bricks: these are a heatsink, even the soft insulating kind don't insulate very well. Fiber wool works so much better

- Uncoated: you need an IR coating.

- One of those stainless steel burners: I could not weld with only one of those: it takes two even after fixing the insulation and coating.

 

There is a frequent member here named Wayne Coe who runs a site that has really good deals on the materials. He'll be along soon to give you his link, I'm sure :)

 

I'm very new to this still myself, and I've never been able to save a failed weld, but that doesn't mean it's impossible... just that I don't know how.

Edited by Ted Stocksdale
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Theoretically I believe you can salvage a failed weld by letting it soak at welding heat in a reducing atmosphere for 10-15 minutes and then resetting it.  To me it would be the same idea as fluxless welding.  I can't say as I've ever tried it though.

 

Check out Geoff Keyes thread in Tools and Toolmaking called "Blown Burners a Care and Feeding" he details out a super easy method of building a blown burner that will suit most of your needs.

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Thats gotten nowhere near forge welding temps... the others have already covered your forge-

 

So, did you weld all the way around your stack? I'm having a hard time seeing the edge in your pics.

 

If so, and its welded well- all the way round... I'd say you're good. Save it til you can get it hot enough.

There should be no forge scale built up in it.

 

If its just tack welded in spots- cut thru the tacks with a cutoff wheel, seperate the stack and clean em up with a sander back to bare metal.

Weld it back up- spray down with wd40, set in a can/jar of kerosene, etc... to keep it from rusting up, and save til you can heat it.

 

Cameras really don't capture the color of forges well... but that baby should be yellow looking when hot.

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Edited by Welsh joel
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Hey thanks Welsh. I did weld all the way around the stack so hopefully I can still use it. If it ends up turning out bad I guess I’ll know that I need to up my welding game lol. 
 

And yeah it didn’t get anywhere past a bright orange. I remember my small little test stacks (couple inches long maybe) that I forge welded and those things were glowing bright yellow and seemed to have welded just fine. Just can’t get a larger piece that hot. 

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The way I was told/taught-

 

Your burner heats your forge, not the metal.

 

The burner heats the forge, the forge retains the heat- and transfers it to the metal evenly.

Getting rid of that brick, and getting a lining that will hold it, and hold up to it- will let you get a more efficient burner that will get you up there.

 

Mines a 1" forced air burner fed by 2" air pipe and a 3/8" gas pipe with a 1/16 orifice hole- i have $45-50 in it from the hardware store... not including the free blower(s) i was given.

 

Forced air setups are more forgiving of orifice size and control... to me any ways.

 

You'll get there! You've got a good head start that I didnt.

Edited by Welsh joel
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3 hours ago, Welsh joel said:

The burner heats the forge, the forge retains the heat- and transfers it to the metal evenly.

Getting rid of that brick, and getting a lining that will hold it, and hold up to it- will let you get a more efficient burner that will get you up there.

 

We need to have that as a pop-up when you log in...   :lol:

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Is that forge REALLY sitting on a wooden bench top and operating ?

Maybe it is a good thing you never got to welding temp.

Hope you have a good fire insurance policy.

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A metal cart is actually on my list along with a new forge. I’m looking for something on wheels so I can roll it out to the driveway to fire it up. I’ve never really liked the idea of having it inside but I’ve just been making it work and keeping lots of fire suppression around (buckets of sand and extinguishers)

 

And I guess I was thinking with the thick bricks underneath the insulated fire bricks, it wouldn’t get the table hot enough to combust. I guess I was wrong? 

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I thought that I could use an old wooden table with a layer of kaowool on top of it to insulate it from my first forge.   I was wrong.  Things got exciting one day. :ph34r:

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Propping up your forge/bricks so that you have an air space between the bottom brick and the wood will help a lot.  You will also be able to see the table start to scorch if it's getting hot enough, whereas now, you'll only know if you're burning the table when the forge falls through the hole.

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1 hour ago, Alex Middleton said:

Things got exciting one day.

Oh man! I’m not looking for that kind of excitement lol. 
 

Thanks for the tip BillyO. I’m probably just gonna go grab a nice metal cart my next day off. Better safe than sorry. 

2 hours ago, Cal G said:

Is that forge REALLY sitting on a wooden bench top and operating ?

Thanks for the callout, Cal. You might’ve just saved me from a disaster. Much appreciated! 

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