Forging scale and damascus billets?

weo

Basic Member
Joined
Sep 21, 2014
Messages
3,020
Hello all. I was forging up a couple of Damascus billets this weekend using my buddy's 300# Chambersburg power hammer and as I was grinding away the scale to cut and stack for the second weld, I got to wondering.

How much do you all pay attention to scale when folding your billets?

My typical stack starts with 18-22 layers and I have been doing 3 separate welding heats, second stack at 4-5 pieces (~72-100 layers), and 3rd stack (usually 4 pieces) to get to ~280-400 layers.

My initial thoughts were that it really doesn't matter as far as the final pattern because of the number of layers.
But it does matter on the amount of grinding between stacks to get to weld-able surfaces. But with a 36 grit belt, it doesn't really take many passes to get to flat surfaces

What do y'all do?

Thanks.

as always
peace and love
billyO
 
To use a belt, you must be grinding on your grinder?
That would require the billet to cool off.
By the time I grind off my scale with a snagging wheel on my 9" angle grinder, the billet is still sometimes red hot!
Can't waste time letting things cool when making Damascus.
 
Karl, what brand and "model" of snagging wheel are you using and where do you get them?
 
To use a belt, you must be grinding on your grinder?
That would require the billet to cool off.
Can't waste time letting things cool when making Damascus.


True, and I wish I had that option, but sometimes I don't. Because it's not my shop/hammer, oftentimes I do the weld at my place, then give it to my buddy to draw the billet out when I'm at work, then on my next day off, I grind, cut, stack and weld, then repeat the process.

But this does bring up a couple related questions. When able to continue without letting it cool, are you merely folding, or cutting into multiple pieces and stacking?
Also, the initial question regarding the scale is still pertinent: My guess is that it's important to minimize the forging scale to minimize chance of voids and imperfect welds. Or is the solution what you said: "By the time I grind off my scale with a snagging wheel on my 9" angle grinder, the billet is still sometimes red hot."?

Thank you
~billyO
 
My guess is that it's important to minimize the forging scale to minimize chance of voids and imperfect welds.
That is done by grinding if off - if that is your routine - Which mine is.
Scale is formed at welding temp - not at a red heat. It's the iron combining with the oxygen - iron oxide - which happens while the steel is very hot.
As it cools down, that has already taken place.
 
I try and do everything hot. I use a chop saw to cut my billets and it cuts a lot easier if it's already red hot. I also use a snagging wheel or also known as a cup wheel. I use the norton blue fire and really like it. It hogs off the scale super fast. If your using grinding belts to remove scale your just wasting money.
 
I often do as Karl and Hoss describe... but also I often will break for lunch or call it a night etc and chop/grind/stack when I get back. This works well if welding more than one billet at a time. I go flux free for the first stack, first weld, then a little flux for the edges on the next couple heats. When drawing I like to get as flat and scale free as possible, brushing the billet hot, keeping my dies clean, edgewise squeezes followed by scraping scale off on the die holder edges.
A snagging wheel or the surface grinder will skim it clean practically immediately if a clean forging is achieved.
I like to use kerosene for second and third stacks, so not a great idea when still red/black hot.
 
I often do as Karl and Hoss describe... but also I often will break for lunch or call it a night etc and chop/grind/stack when I get back. This works well if welding more than one billet at a time. I go flux free for the first stack, first weld, then a little flux for the edges on the next couple heats. When drawing I like to get as flat and scale free as possible, brushing the billet hot, keeping my dies clean, edgewise squeezes followed by scraping scale off on the die holder edges.
A snagging wheel or the surface grinder will skim it clean practically immediately if a clean forging is achieved.
I like to use kerosene for second and third stacks, so not a great idea when still red/black hot.


Salem, I'm curious as to why you do your first weld without any flux and then use it on the succeeding welds. You don't use either borax or kerosene on the first weld?

Is it mainly to prevent any of the flux or "residue" from getting trapped in the middle of the layers?

I know some guys simply use the forge atmosphere to control the scale, but if that's what you are doing, why not just stop flux all together?

Just trying to learn :)



~Paul
My YT Channel
Lsubslimed

... (It's been a few years since my last upload)
 
I also weld without flux. I do as Salem I dry weld my first stack and then use light flux. When dry welding it does not normally weld the very edges. Then I draw it out and chop it up hot. Then grind and restack. I have tried welding them togather with the mig and also just welding the corners. If you weld all along the seam then it will weld to the edge. Or use flux to finish the edges if your just welding the corners. But all welds need to be removed befor further work like twisting or stacking. So less work is better.
 
I guess my way of thinking (although I have have only forged a few smaller billets of damascus over the years) is that if you're going to use flux at all, why not use it during the first weld to ensure that there is no scale? I understand the use of kerosene in the latter stacks, but not quite the lack of flux to begin with.

Are you guys more worried about fluxed getting trapped than scale? It seems like it wouldn't make a difference in time or trouble to add flux before the first weld if using it for the edges on the next.

I'm jut trying to figure out if there are really any advantages to not using any flux for the first weld. I may be over-thinking it though, due to my lack of actual experience in this area.

Thanks :)

~Paul
My YT Channel Lsubslimed
... (It's been a few years since my last upload)
 
The advantage is that flux sucks. Eats your forge and yes it can get trapped in your welds. Plus sticky gunk gets all over your forging dies. Flux is used to remove the crap that you should have removed befor you stacked the billet.
 
Everything above makes sense, thanks to all.
Looks like I've got a few new things to try (and a new tool/accessory to buy).

Out of curiosity, how thick (read: tall) of a stack do y'all make? I've been limiting mine to ~4" max but have also done all my previous welding heats by hand with a 4# hammer. If I use his power hammer, how thick could I go?

Again, thanks for the replies/answers.
~billyO
 
Funnily, I usually do the opposite. I'll set my first weld wet, because it's typically fool-proof, and when you've got a large initial stack (my initial stacks are usually 3" tall) for many of my patterns, and the vast major of patterns I build are re-oriented end-grains or "mosaics". My experience has shown me a higher consistency of good welds on the far edges of billets with flux, and with the above type of patterns, it's pretty important, as I like to re-orient and draw them very thin for making W's and those types of patterns get as much action in the first weld as possible, while having to grind away the least amount of "lines" on the edge once it's re-oriented.

If you don't make a lot of these types of patterns, this probably makes little sense to you, as with side-bar and pressed in patterns, you almost never bother with the edges, and by the time you've restacked a few times, and the billets wide, the loss is pretty minimal, lots of people that sell damascus, myself included, usually don't bother even grinding the edges, and most people just know to stay away from the very edge, but it's a whole different game with complex mosaics and end grains, where if things go wrong, you can chase a bunch of the billet grinding past any bad edge welds once they're re-oriented to the top and bottom of your billet.


So I typically do my first weld wet, and then all subsequent welds dry. For me, it's the fastest, with the most consistent results. After a couple of restacks, there are no "flux lines" to be seen in the finished billet, and I can't remember the last time I've had a flux inclusion. I've heard some "myths" bandied about about this or that weld style being stronger than flux welds, but I've seen no evidence that this has been tested under any objective scenario.

To be clear what I'm referring to here are not bad welds, I'm referring to the depth on the sides where the weld isn't perfect. Which is something you only ever notice when you're reorienting billets 90 degrees, which of course, can put a minor flaw, right in the center of your billet.


Also, flux is a buffer, a shield, from oxidation and carbon burn off, that's what will keep welds from setting properly. It's not soap, it doesn't clean anything out. You can hydrocarbon or fluxless weld rust and mill scale covered stock easy as pie if you know how, and the rest of your process is right. However, flux has it's advantages even if you aren't using it for welding. For patterns with a large number of restacks or extensive soaking sessions, a light fluxing can mitigate a significant amount of over-all decarburization. Even if you have a perfectly reducing atmosphere, without anything protecting the billet, you'll notice significantly increased scale formation,as soon as you pull the billet out of the forge, an order of magnitude higher than if the tiniest bit of flux is sprinkled on the outside of the billet, and there hasn't been any real research to see how amplified the carbon burn off is inside the forge without flux.


I'm not saying it's perfect, and I use it only under particular circumstances and sparingly, but this recent trend of vilifying flux has gotten a bit out of hand in my opinion. It's a tool, that has advantages and disadvantages like all do. I don't think it does any of us any good to pontificate in absolutes, just because a new trend has come into favor.

I personally use all techniques, depending on the pattern, the size and end shape of the billet, the starting material, and whatever other caveats come into play for a particular job. It's important for all of us to find which techniques work best for us with our equipment, materials, and process.

Also, thousands of the best knives ever made by the best makers of our time, were made with damascus where every weld was done dripping flux, with nary a flux line to be seen, inclusion, or other imperfection, in the finished product. Flux lines go away after HT, because they're not trapped flux (they're weld zone discolorations), unless there's a significant problem with a weld otherwise. The only time it's really an issue, is for someone like me who sells damascus billets to other makers, they're unsightly, mostly, because of a large amount of mis-information being proliferated by people that aren't as knowledgeable about the subject as the purport themselves to be. I will say that if you do have a major flux inclusion, at least you will typically notice if before you're making a knife from it, as it'll usually cause a significant blister, which is plain as day. An isolated bad weld area without flux, will not make itself known until you grind into it.

It's easy to avoid them, because dry welding (after the initial) stack, is efficient, and also fool-proof, and has become my preferred technique regardless (dry welding the initial stack is on the other hand, excessively tedious, you have to either build a can, which is time consuming, or weld the entire sides up with whatever your preferred method is, even MIGing at light speed, it takes forever), so no big deal, but is there any objective evidence that one method or another yields a better result? Not that I've seen, unless I've missed something since Kevin did some pretty extensive testing of flux and fluxless welds, which didn't from my reading, yield any conclusive evidence one way or another, although many people chose to interpret it the way they already "felt" was better.

To be clear, when I say dry welding, I mean welded seams or canned welds (they're fundamentally the same), not hydrocarbon or just open stacks with zilch, although I've done many hundreds of those welds successfully also, for me though, every once in a while I'll get a "rogue" bad weld or inclusion, with the open stacks with no hydrocarbon or anything, that I typically can't explain, and trust me, I'm not welding by feel. I've got pyrometers, timers, and an extensive process, that usually, is foolproof. Although I'm sure I've just jinxed myself. ;)


Also, there are kiln washes that can be essentially flux proof, and plenty of options to reinforce a forge that flux can't touch (super high alumina extreme duty firebrick for example). Unfortunately, in the knife world, not many people have ever delved deep enough to figure this out, other than offering a few limited, super expensive products, in a range of thousands, that the rest of industry understands.



Sorry, I know this ended up being a bit of a rant, and I'm not trying to call anybody out, I just hate seeing blanket "dogma" being passed out as objective truth. I know it's the nature of social groups to try and distill everything down to a specific consensus, but as craftsmen, I don't think we do ourselves any favors trying to assert absolutes in such complex areas of the art. Hell if we really cared about having the best scenario from the standpoint of the steel when forge welding, we'd probably be doing our welds in charcoal, since it's pretty much the optimal medium to assure no net carbon loss, at least, when it's perfectly setup and tended, but I think most of us agree, that's simply too tedious, and allows too much room for error, when things aren't perfect.
 
Last edited:
Re-reading your posts above, it looks like you guys agree with me about the edges. Clearly we just use a different approach to compensate for this. I'm a big proponent of all of us finding what works best for each of us, and not judging someone else's technique as long as the results are up to snuff.

I guess most I felt the need to address the "flux sucks" issue, which I disagree with, it's neither good or bad in my opinion. It's just a tool, with limitations, like they all are.
 
When I said flux sucks I did not mean it does not work, we all know it works. I mean it's messy and rather frustrating some times. I was not trying to bash the flux just listing the reasions I use as little of it as possible. My forge floor is so thick with flux and scale that I just about can't get a billet in it any more. Some of my best and easiest welds have been when I wrapped the stack with heat treat foil and folded over the ends. But I don't make tons of Damascus, just what I need for my projects.
 
This brings back a good memory.
Dr. Jim Batson was giving a demo on making damascus up at Bill Moran's hammer-in, and I was helping him. He pointed out that the scale is only an issue if it cools below 1600F. Above that a quick swipe with a steel brush removes anything that is on the billet surface. He would never let the billet get below red once he started. He would weld - brush off - reheat - brush off - reweld - brush off - reheat - etc. Once the billet was drawn out enough we hot cut the center, brushed off, reheated, folded reheated, welded, etc. If he let the billet cool below red for any reason, he cooled it off and ground all surfaces on the belt grinder to bare metal. It only took an hour to do seven folds and end up with a 256 layer billet ready to forge into a knife ... of course, Jim knows what he is doing. He would look at the group and say, "This isn't rocket science." ( Jim is a NASA engineer)
 
Back
Top