Forge welding, how to see when it's ready?

[anvil]

Lol, I've done that in broad daylight at a crafts fair.

As an example, about 20 forge welds, all to dimension and all done with 20 mule team borax. 

 

[ThomasPowers]

Very nice, very "Kuhnish"!  I've seen Dorthy Stigler demo at Quad-State and take time to sling the molten borax off her steel on the way to the anvil for a forge weld.  I've also seen the late Billy Merritt at the IBA conference weld at temps I would would consider cool for forging!

[anvil]

Slinging borax is the way to go. I think it's a Turley trick

The bird is directly from Kuhn. The other three critters are mine using techniques I learned from the bird. I called the monkey " the monkey from hades". This screen was for a nursery and it took the "devil of time" to make it not look like something from a Steven King novel.

This was my first attempt at doing a perspective "drawing" in iron.

The gate is actually hinged and actually worked. However discretion was the better part of valor and I did not think it would survive in a nursery. Also, the gate pickets are all mortise and tenons.

As far as forge welds, all corners are forge welded and the scrolls around the perimeter are one piece due to forge welding. The corner welds are a bit difficult, but the rest are just very basic welds that one can do after learning to weld. 

Forge welding to dimension, or just plane forging to dimension, in my opinion, should be a goal always kept in mind until it becomes second nature. 

Forge welding at lower temps comes with experience.

 

[Frosty]

That's one heck of a piece of work Anvil. You didn't completely avoid the Stephen King vibe though but that's okay. 

Frosty The Lucky.

[ThomasPowers]

ISTR several Monkeys looking like that in my pre-war copy of Kühn's  "Geschmiedes Eisen".

Putting a flickering red fire behind the shapes should be great for throwing "interesting" shadows around the nursury!

 

[anvil]

Actually, I did this a long time ago, and am not sure if the other critters are in his books or not. I just don't remember. I do try to credit what I do to where it came from. It kinda keeps a continuity to our traditions alive.

Lol, the monkey still gives me nightmares, and you are right, I never was able to complety get rid of the devil in the monkey.

I did a set of four fire screens for the W.C. Fields estate in Beverly Hills.  That alone ought to be worth a free beer in any bar worth a hoot.  Not bad for living in Corado and no advertising.

[ThomasPowers]

Should have added a corkscrew on the Monkey's tail!

[anvil]

If you look, you will see there is a little slit in the scroll that the tail"corkscrews" thru and becomes a point of attachment 

 

On 6/29/2021 at 8:15 AM, ThomasPowers said:

"Kuhnish"

Thomas, thanks. I actually did the bird to see how close I could come to emulate Kuhn's work. And the other critters are definitely in the same style. Your recognizing this is quite an honor. I guess I succeeded. Often when we do things within our work, we don't do them for just everybody. We do them for the few who will recognize these details. You are the first, and it's been worth the wait. Thus my thanks.

[ThomasPowers]

No I am honored!

[DennisCA]

I gave it another try this evening, my flux powder and brush came. I took it slow and didn't run the fan on max, I let the sit until yellow heat then I added flux.

I thought I got it, once I even got sparks by misstake, but when all was said and done it hadn't taken and I hadn't gotten any welding done. I dunno why I thought I was being real quick about it, two steps from forge to anvil, planned it out ahead how I should proceed, struck with a lighter hammer too. Mostly it seems I created a lot of scale and burnt a little of it. I dunno if I put it in the oxidizing portion and that's why it never took. Might be I need to reconsider something about the forge, I was pretty mellow with the fan, perhaps I should try and build the coke mound higher with bricks and place it higher up in the fire and see if that makes a difference.

 

[Frazer]

Just to make sure we're on the same page, you brought it up to orange/yellow, added some flux and then put it back in the fire, yes? Sorry, that's probably a dumb question.

I usually heat up both pieces -- or just the one depending on the weld -- to just below welding heat, give them a good brushing, flux, and then back into the fire to bring them up to a full welding heat. Some people say to flux at a dull red and add more later. To me, that depends on the weld since a billet ~= scarf weld.

Quick questions..

What are you trying to weld? (type of weld/size of material)

As a test, if you bring 2 pieces up to a welding heat do they start to stick to each other in the fire?

Did you really expect to get it on the first few tries?  *joke*

--

Making lots of scale while it's in the fire isn't really a good sign.

Sorry that's all I have at the moment.

Oh, I don't know if you're trying to do a scarf weld (if you are, maybe try something a little easier), but Mark Aspery's video called "Scarf Theory" does show a pretty good demonstration of what a welding heat looks like.. Might be educational if nothing else.

 

[ThomasPowers]

Billet or a "drop the tongs" weld?

I flux when it's barely glowing---if not sooner! 

If it's scaling while it is in the fire you do NOT have or are in a neutral to reducing zone.

How deep are the hot coals under the piece, also over the piece?

[DennisCA]

I was trying to weld this ring I have for a scythe, it's 6mm steel originally, so it basically hold itself in the right position, the ring overlaps and that's what I was trying to forge weld together. I dunno if it was scaling in the fire or not, I tried looking and I didn't see it scale up, but I had a lot of scale afterwards and no viable weld. 

It looked like that when I put it in the fire, it worked without the weld since it was thick enough. But I still wanted to try and get it done.

Will post some pics with measurements of forge.

Here's a photo of the firepot, total depth seems to be 2 and 13/16ths as well as I can read this inch ruler I got. I think the inside of the pipe is between ½" to 3/4" below the floor of the forge at the 12 o'clock position.

I try and place items in the forge so they are level with the floor of the forge, then I scoop coals back over it and it probably covers it an inch or more with coals, I try and pile it as high as I can while also having lots of coals on the sides.

When I removed the coals I noticed the bottom of the pit had risen, was a fused mass of sand and I believe clinker, I broke it up and replaced it with ash instead, so the depth of the "firepot" was actually less than in the pictures when I attempted the welding. Might've had an effect.

[Frazer]

Right, right, I remember you said it was a ring, my bad. I would consider that to be more of a collar, but thanks for the picture. It might be worth doing some experimentation with a simple faggot weld. Take a piece of your 6mm flat stock (or any scrap you have laying around), hot cut it ~3/4 of the way through, fold it back on itself and weld it back into the parent bar.

Keep in mind to get a seamless weld, it does have to be worked together quite a bit. I have always heard this called "refining the weld". That is also why you generally upset the two ends to be welded so you have some extra material there for refining your weld. Without that extra material you end up with a thin spot on either side of your weld. 

Refining the weld on a collar like you have might be kind of tricky unless you make a tool that can be put into the collar to support your hammer blows without damaging the rest of it.

I've never tried making something like that, so I'll defer to others' recommendations.

[ThomasPowers]

"refining a weld" also make it a stronger weld.

[Frosty]

You are using a "side blast" forge so coal under the work isn't as important as it is using a bottom blast. If you are laying your work where you are measuring the depth you are too close to the tuyere, move it farther away. 

With a side blast you can actually look inside the fire to determine where the heart is. I just lift an edge with a SMALL shove or fire rake to peak inside. Follow the fireball back from the blast until it starts to dim from orange. This is a strong carburizing zone, moving towards the blast it will get brighter orange until it begins to turn yellow I like to weld just about there. Moving closer to the blast it gets YERY yellow and is strongly oxidizing. 

With a little practice you can preheat your ring with the scarfed weld surfaces facing away from the blast and FLUX much sooner. My trick is to close the joint after sanding/filing till it's shiny cold with a dusting of flux between the pieces. That way before the steel reaches  temp where it'll oxidize on contact with air the flux will have melted and covered the shiny joint surfaces. Then I brush and add a little more flux to be sure.

Once your ring is up to red and you've brushed and fluxed it you can either move it closer to the blast or give it more air. The more air you give it the farther the heart of the fire will move from the tuyere pipe. Make sense? 

When your ring is orange simply rotate it in place till the joint is facing the blast. You can watch it by carefully lifting the coal on the side of the fire and peaking. When it's a high yellow, I call it watery or flickering yellow because you can see color changes literally flickering in the steel, it's ready to weld.

Two steps is a long way, move your anvil closer if you can, sometimes I'm almost reaching over my anvil to the stock in the forge. I'd weld this ring over the horn of my Soderfors, it's long and tapers to a sharp point. If it wouldn't fit over the horn I'd make a bic, a piece of solid round fitted to the hardy hole and bend 90* so it hung over the edge of the anvil.

Set the welds with a moderately heavy hammer 1000g isn't too much but don't get crazy or hit it HARD. Two or three good firm "dead" blows works well for me to set the weld. Brush reflux and return it to the fire.

Repeating the same steps as setting the weld will refine it making it bond completely over the entire joint surfaces. After a couple refining welds it should be good to forge as you wish.

Frosty The Lucky.

[DennisCA]

It's about there I place the piece. My mound drops off though so moving it farther to the right would be difficult, I was looking at a torbjörn åhman video last night before I went to sleep, he made a side blast JABOD and running coke like I do. He made the firepot relatively deep and the tuyere was further down, but the pot was not as not wide, reminds me of how a charcoal forge might be shaped, he got to welding heat no problem in it. I was thinking the shape of the firepot probably means the air hits a wall and is forced to rise upwards through the coals. 

I thought it was an interesting note. I will use another brick for now I think and pile the mound higher on both sides, so I can move the piece further away from the tuyere and see what that does.

 

[Frosty]

The only change I'd make in the first forge is using fewer rocks but that's a fine example of a JABOD. Humans have been using the ground version as long as we've been hammering on metal.

Frosty The Lucky.

 

[pnut]

7 hours ago, Frosty said:

only change I'd make in the first forge is using fewer rocks

It bugged me too. I like the video but am hesitant to recommend it to beginners because of the possibility of spalling. I really want a slab of soapstone. I had a pretty large pizza stone that I never used so I left it when I moved. That's the reason I am a packrat. I throw something away and it taunts me later on when I find something it would be perfect for. Oh well. 

Pnut

[anvil]

Im not a side blast man, but i do believe no matter where the air comes in, you need to consume all the O2. A good rule of thumb is 4" of coke below your work, and 2" above. I watched his vid to see how he achieves this. He made two firepots, one from stone and one from brick. The second try with brick, he put a brick on top' of the air inlet. A brick is ~4" tall. Notice he banks the coal nearly to the top of the brick. If i did this experiment, my third attempt would be to make a brick firepot ~10"x14" to match my size in my shop. Its a Centaur Forge rectangular pot, ~4" deep and ~ 10"x14" at the top. I would lay the brick to define this shape and the bottoms of the bricks would be in plane with the one sitting ontop of the air inlet. Id work my iron parallel to the forge and sitting on top of the brick. This now gives me a sideblast firepot 4" deep and 10"x14" at the top. When my iron is in the fire, I would put another ~2" of coke on the top and see how it worked. This  matches my bottom blast, and should work for a side blast as well. I suspect there would be a couple more trys to dial it in, most likely to modify the bottom so as to better direct the air flow, but Im pretty sure this would work pretty well. The final step would be to make it out oh a fire clay/ fire brick. And like he did, I'd make sure there was space under the air inlet for the clinker to go. 

I think your major problem is not enough coke around your work to consume the O2

[Frosty]

There are good fire stones, sandstone being porous enough not to trap steam. However without testing or buying something suitable I'd go with 3,000f hard fire brick. The too much stone I was referring to in the video was the ones he was using as filler in the box. Dirt is lighter than rock, even compacted to max density. 

Soap stone or a pizza stone is safe from spalling but soap stone is chemically the same as asbestos with a different molecular water content and soap stone makes dust REALLY easily. 

I had to look up pizza stones and some are stone but most are unglazed stoneware ceramic. I don't think it'd take the heat of a forge fire.

Frosty The Lucky.

[DennisCA]

This about firepot depth in bottom blasts is also something that I find tricky Anvil, torbjörns regular cast iron firepot is only 2" deep and he does forge weld in that too. I find it strange tbh how there can be such variation in pots.

 

Anyway I looked at my forge last night and I ran it and what I could see the fireball seems to keep to the left, near the tuyere, as if the air rises upward quite quickly, doesn't propagate very far to the side. The heat seems to be quite localized thus, trying to heat a stock on the right side took a very long time, those coals where not even glowing. 

I had a piece of stock in the fire and I kept looking at it to see if it was scaling. But I couldn't say for sure if there was scaling going on or not, sometimes there seemed to be some but might've been because I moved the stock too far to watch it. Other times the stock looked clear, but might have a couple of tiny spots that I wasn't sure if they where oxidization or not.

So my idea is I need to make the pile higher instead of wider, or both.

[pnut]

My JABOD had the same problem with the hot spot being right next to the air inlet on the one side of the trench. I angled the pipe down slightly and it moved it about an inch or two towards the center. It was a noticeable improvement. 

I had to train myself to stop being greedy with the fuel and pile it on. In my jabod the stock is probably two inches above where the air inlet is with a good pile of charcoal on top. It's usually piled up a few inches above the hearth at a minimum. Here's a picture of my old jabod after the fire burned down. The tuyere is three inches below the below the hearth on this one and you can see the bricks to mound the fuel up and below it is a picture of the firepot.

Pnut

[DennisCA]

That's a simple change to try, I'll see what angling the tuyere downwards does for the fireball shape. 

[anvil]

I only know Torbjorns from his YouTube vids. He is amongst the few that are worth watching. His "presence" at the forge is worth emulating. Beyond that, I have never seen any of his work, nor have I noticed the size of type of his working firepot. Fwiw, I've worked with a few smiths across the big pond as well as here in the US. I have never worked in a situation where 4" of coke wasn't the norm. I'm not a collector of tools, yet it's hard to not see what's available, either for sale, auctions, or at blacksmith conferences. I'd have to say that the most common size fits the dimensions above. Centaur sells a 2" deep 12" round firepot they label as a farriers forge. I do know that the shallower your firepot, the limit is size of iron you want to work. Not that you can't, but let's say, you might want to pack a lunch. So, if I were to make a cast firepot 2" deep I'd call it a farriers firepot or call it an affordable intro level firepot. 

So, again, you have a problem. Your description indicates you have an oxidizing fire. This happens when your fire won't consume all the O2. This tends to happen when your work is too close to the air inlet. You can solve this by decreasing the voluume of air, or increasing the amount of coke between your work and the air source. If you decrease the amount of air, the effective size of stock you can work decreases,,, meaning plan ahead on what you want for lunch.

13 hours ago, DennisCA said:

my idea is I need to make the pile higher instead of wider, or both.

Correct, and when you do,shoot for about 4"  and place your iron on top, with about 2" of coke over this. Then Increase the voluume of air in order to make a bigger neutral/reducing fire.