What is the process that takes place when using this technique? Forge Welding.

Fred.Rowe

Fred.Rowe

Knifemaker / Craftsman / Service Provider
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I switched from borax to hydrocarbon solvent, to weld damascus, last year. I am very satisfied with the results but for the life of me I can't wrap my head around what is taking place in the forge as the hydrocarbon solvent is being consumed. How does the carbon jacket form and does it form all at once or overtime as the billet is heating?
I reason that the solvent between the layers is building the jacket, by coming to the surface, as the heat rises, but that could be completely off base
If there is a chemist in the audience help me understand this process.

Thanks, Fred
 
I am by no means an expert but since there is no one here to say anything I will chime in hehe. I read up a lot on this in the last year before I started my first forge weld. It came up on a couple blacksmith forums as well as some of the knife forums. I used methyl hydrate but others used kerosene or lamp oil which, while not the same substance, does pretty much the same thing. I dont believe it has anything to do with the billet heating as much as it does with the actual burning off of the solution. I assume you soak the billet while your forge is heating so once you put it in, the solvent starts to burn immediately forming soot in any space available. This will stop any oxides from forming while heating. Not sure how much of a jacket this makes but thats my understanding of the process. Having said that, I made my one billet with 5 layers of 1084/15n20 squeezed in a vise and wired together, no tig/mig or handles welded on or worry about anything else. I soaked it, put it in the forge, got it to heat and let it sit for a bit, then took it out and worked it. Im pretty sure it took in the first heat but I did two more welding heats before I forged it down.

Or I could have just linked you this... http://www.americanbladesmiths.com/ipboard/index.php?/topic/57-kerosene-vs-flux/ hehe

Sean
 
tattooedfreak said:
I am by no means an expert but since there is no one here to say anything I will chime in hehe. I read up a lot on this in the last year before I started my first forge weld. It came up on a couple blacksmith forums as well as some of the knife forums. I used methyl hydrate but others used kerosene or lamp oil which, while not the same substance, does pretty much the same thing. I dont believe it has anything to do with the billet heating as much as it does with the actual burning off of the solution. I assume you soak the billet while your forge is heating so once you put it in, the solvent starts to burn immediately forming soot in any space available. This will stop any oxides from forming while heating. Not sure how much of a jacket this makes but thats my understanding of the process. Having said that, I made my one billet with 5 layers of 1084/15n20 squeezed in a vise and wired together, no tig/mig or handles welded on or worry about anything else. I soaked it, put it in the forge, got it to heat and let it sit for a bit, then took it out and worked it. Im pretty sure it took in the first heat but I did two more welding heats before I forged it down.

Or I could have just linked you this... http://www.americanbladesmiths.com/ipboard/index.php?/topic/57-kerosene-vs-flux/ hehe

Sean
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That makes since when you think about it. I do soak while heating the forge and the blaze is going as soon as the billet goes in, so I think you are right, the jacket must form fairly fast. Have you looked closely at the carbon jacket after pressing? The carbon is 1/16 of an inch thick that forms on the surface of the steel; I'm amazed at how the jacket forms to any shape you want to weld.

Thanks for your response! Happy New Year Fred
 
Fred, I think the "jacket" forms shortly after you put it in the forge. I use kerosene and you can see when it is done burning itself up.
 
OK, from a chemist:
The hydrocarbon liquid is a combination of hydrogen and carbon...thus the name.

When placed in the hot forge, the liquid rapidly super-heats, and the hydrogen combines with the elemental oxygen in the forge chamber. This leaves a "jacket" of elemental carbon covering the billet. Carbon combines with oxygen and gasifies at 1350F (IIRC), so any available free oxygen is absorbed by the carbon. This prevents the iron in the steel from combining with the oxygen, and leaves a surface that is very agreeable with fusing with any similar surface. Any carbon remaining in the joint is diffused into the joint at the time of the weld, and actually makes the fusion happen at a lower temperature. Thus, the billet welds easily.

The old borax system relied on a coating of liquid boron glass that covered the surface and kept oxygen away. It did this very well, but also could keep the two surfaces from fusing.
 
My thoughts on this and why it works so well . Using a hydro carbonlike others have said burns off leaving a thin layer of carbon on all parts of the billet. as the steel heats up it absorbs the carbon making a minutely thin layer of cast iron which as we know melts at a much lower heat than the rest of the steel in the billet. This lets everything fuse together. during farther heat forging cycles the higher carbon areas at the bonding layers is absorbed into the billet leaving a very clean billet without the tell tale lines seen in billets welded with flux. On the other hand I could be totally off on this and just going along with my head up my a$$. So if anyone has a better theory I'm all ears.
 
bladsmth said:
OK, from a chemist:
The hydrocarbon liquid is a combination of hydrogen and carbon...thus the name.

When placed in the hot forge, the liquid rapidly super-heats, and the hydrogen combines with the elemental oxygen in the forge chamber. This leaves a "jacket" of elemental carbon covering the billet. Carbon combines with oxygen and gasifies at 1350F (IIRC), so any available free oxygen is absorbed by the carbon. This prevents the iron in the steel from combining with the oxygen, and leaves a surface that is very agreeable with fusing with any similar surface. Any carbon remaining in the joint is diffused into the joint at the time of the weld, and actually makes the fusion happen at a lower temperature. Thus, the billet welds easily.

The old borax system relied on a coating of liquid boron glass that covered the surface and kept oxygen away. It did this very well, but also could keep the two surfaces from fusing.
Click to expand...

or this could be it.
 
As stated, oxygen and the attendant oxides are the enemy. That is what makes forge welding stainless such a bear or so I am told. The chromium oxides that make it stainless also make it not want to stick. Without oxygen a lot of metals WANT to fuse together. In a vacuum, they will eventually do it a room temperature or lower. Just ask the astronauts about having to break bolts loose.;) Before anyone even mentioned it here, I was wondering if that layer of extra carbon might lower the welding temp a tiny bit because we know that high carbon steel welds at a lower temp that your typical low carbon steel or iron that blacksmiths typically use.
 
I know the technique works but now I can see why it works so well.

Thanks for your input, Fred

Shop Talk has been a boon for me; its added so much to the enjoyment I feel when I'm working in the shop.
 
How fragile is the carbon jacket? I have heard that you have to be pretty careful with it while in the forge. I have a venturi forge, and it has hot spots, so I rotate the billet to get a more uniform heat. If I bump the walls or floor, or what ever, do I have to worry about fracturing the jacket? Do you reapply any thing for flux after the first heat?
Sorry for the hijack, maybe I should have started a new tread.
Thanks,
Cody
 
Cody Hofsomme said:
How fragile is the carbon jacket? I have heard that you have to be pretty careful with it while in the forge. I have a venturi forge, and it has hot spots, so I rotate the billet to get a more uniform heat. If I bump the walls or floor, or what ever, do I have to worry about fracturing the jacket? Do you reapply any thing for flux after the first heat?
Sorry for the hijack, maybe I should have started a new tread.
Thanks,
Cody
Click to expand...

Your question is on point. The jacket is somewhat fragile but the billet can be shifted as its heating. I treat it like glass and avoid sharp corners and edges that might crack the jacket.
Just repeat the process for the second and successive welds. Try it with a couple of pieces of scrap you have lying around and I think you will find use for this technique. I don't miss the borax one bit.
 
Bill has the basics pretty well stated in layman's terms.

OK, some more chemistry

Methyl Hydrate is a fancy name for CH3OH....AKA Methanol...
Denatured alcohol is ethanol (CH3CH2OH), plus 10% methanol (CH3OH), plus a tad of methylisobutylkeytone (MIBK) - [CH3)2CHCH2C(O)CH3] to make it undrinkable.
Kerosene is C12H26 ( called dodecane by the pocket protector crowd)

As you can see ( well, some of us can see), the methanol has one water molecule attached to a methylene molecule (one carbon atom bound to two hydrogen atoms). In burn off, the water will leave, the hydrogen will combine with oxygen, and you get one carbon atom per molecule of methanol for the steel coating....not very efficient. Denatured alcohol isn't really much better.

Now, lets look at that kerosene. There is no water or oxygen to cause problems, twelve carbon atoms to add to the metal, and twenty-six hydrogen atoms to carry away oxygen. The value as a flux is easily far greater to see than methyl hydrate.
 
I am going to give this a try. Lampoil will do? I ask this because in holland we have the names for liquid fueles a bit mixed up. US kerosene in holland we call petroleum.
 
erik,
The best way to choose is to get the formula of the oil. If it is basically a C#H# product (eg. C12H26) then it will work well.
If I remember correctly, kerosene is also called paraffin and paraffin oil in the UK, but I don't know about Holland.
I would suspect that lamp oil will work, but check it out if you can.

Gelukkig nieuwjaar
 
Phillip Patton said:
Would you have to let it cool to room temp in between welds? This sounds very interesting; I'll have to try it.
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On the first weld, which I run at 2250; press the entire billet at once and draw. There will be several "layers" of the jacket that pop off as you press the billet from side to side. After the billet is drawn to length; grind the surface clean cut and stack and tack weld.

When you are putting the original layers of the billet together; if some of the pieces are on the thin side, weld the billet at one inch intervals along the sides to keep the billet from moving during heating; this can cause the jacket to crack when the steel expands.

Let the billet cool after welding so as not to run the risk of a flame up when placed in the hydrocarbon solvent.
 
Phillip Patton said:
It sounds very inconvenient and inefficient. I suppose if you have to take a second weld (best to do it right the first time), you could just use borax.
Click to expand...

There is no need for a second weld if the process is done correctly. This is identical to using sealed stainless cans to weld in.

I think you will find that because the success rate is so high this technique is very efficient.
 
Fred.Rowe said:
On the first weld, which I run at 2250; press the entire billet at once and draw. There will be several "layers" of the jacket that pop off as you press the billet from side to side. After the billet is drawn to length; grind the surface clean cut and stack and tack weld.

When you are putting the original layers of the billet together; if some of the pieces are on the thin side, weld the billet at one inch intervals along the sides to keep the billet from moving during heating; this can cause the jacket to crack when the steel expands.

Let the billet cool after welding so as not to run the risk of a flame up when placed in the hydrocarbon solvent.
Click to expand...

I'm using a hammer, not a press. Is that going to be a problem? Nevermind, I'll just try it. On some cheap steel. :D
 
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