First laminated steel - the search for the lost core

Stromberg Knives

Stromberg Knives

strombergknives.com
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Hi guys!

Did my first billet of laminated steel, I chose 15N20 (3mm, 1/8") with 1095 (3,5mm, 9/64") as core. I surface ground the three pieces and welded the seams all around. The length of the billet was about 4 inches.

Then I heated the billet up to about 2250 degF and let it soak. After that I gave it some light taps with the power hammer, on both sides with an additional heat in between.

Then I drew it out with the power hammer, careful counting hits per side, to about double the initial length (from 4 to 8 inches).

I then let it cool and then ground one of the edges to see where I ended up with the core. I tried etching with 2:1 (water to FC) and 5:1 (water to FC). With the same result: it etches, but no contrast shows, so I cannot locate the core.

It looks, from a novice point of view, as I managed to get the forge welding right, but what went wrong afterwards? Any ideas?

The steel was bought from a reputable source in Finland.

9E19d64.jpg

k1DKOck.jpg

7G1sGsR.jpg
 
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Yep, when you weld all the way around that outside weld bead will be thicker than you expect. Perhaps even a 1/4" or so might have to be removed. Bet it shows nicely once you get there.

Take the grinder and grind a notch into the edge, going 1/8", etch, 1/4" etch until you can see the core. That will show how much you've got to remove from the edge.

Most folks don't seal weld all the way around on a carbon to carbon weld, only do the seal weld when using SS on the outside layer with a carbon center layer.
 
Latest update.

I ground off a nice chunk and etched again, but still I wasn't able to see the core. So I made a knife out of the billet instead, hoping it would reveal itself on the bevels. Since the core didn't show, I did the surface grinding and bevel grinding blind. But that's okay since it's just a practice piece, to learn from.

I heat treated it as 1095 (the core) and tempered it to 64 HRC. Then I hand sanded it to 800 grit and etched it in 5:1 FC. It seems my 15N20 and 1095 etch more or less exactly the same, and that's why I had trouble finding the core. I wonder why? I tried both longer and shorter soaks in FC, with the same greyish result.

Even after reading a lot of older 1095/15N20 threads here at the forum I can't really see what I've messed up. Could it be the steel properties?

D2if0z5.jpg
 
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Those two layers (core and outer) sure are about the same color for sure. The divider between the two shows up nicely so you know you've got a nice San Mai there. I did a 1095/15N20 billet and I was thinking there was a nice difference in color after etching. Looking back over some photos and a thread of my first San Mai billet it seems I used mild steel for the cladding over 15N20, and the 15N20 comes out of FeCl etch really black. Take a look at this thread to see:
https://www.bladeforums.com/threads/1st-attempt-at-san-mai-billet.1635728/
Post #1 has a photo of the flat side and top view (fuzzy) showing the black 15N20 core. Post #6 shows a nicely etch after blade is profiled. Did you really clean the billet before etch?
 
In the future it might also help ya to clean off the oxides after etching the rough forged billet, since they seem to wipe off more cleanly from the 15n20, even with something like some used 2000 grit paper.

ETA: Also, I could be wrong here, but for some reason I think I remember reading something about Aldo's 1/8" and thicker 15n20 being a different composition than the thinner, unless it was simply that it was a custom smelt, but maybe it affects the etch? Maybe somebody who's used 1/8" + in their damascus might chime in on how the results were. @javand Have you tried it in your billets?



~Paul
My Youtube Channel
... (Just some older videos of some knives I've made in the past)
 
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Two things come to mind:
1) The etch shown doesn't look dark. Have you checked your FC to see if it isnt active anymore?
2) The 15N20 or the 1095 isn't what you thought it was.
 
Where did you get the 15n20 is my question. One way to see layers is to grind the edges clean on a corse belt while the billet is still hot. Does not need to be red but hot enough to oxide the steel. Also grind perpendicular to the bar not parallel. This really makes the layers pop and you don’t need to etch.
 
Stacy E. Apelt - Bladesmith said:
Two things come to mind:
1) The etch shown doesn't look dark. Have you checked your FC to see if it isnt active anymore?
2) The 15N20 or the 1095 isn't what you thought it was.
Click to expand...

1) I thought of this and made new diluted FC from two different bottles/makers. With the same result.
2) Yes, you never know. The steel was bought from Brisa in Finland, a reputable knife supplier here in the Nordics. But I was actually annoyed by the fact that both the 1095 and 15N20 were poorly marked with small writing on only one side/end. The bars differs in thickness though so I’m sure I didn’t get them mixed up in the process. Maybe I should get some new steel from an other supplier, just to be sure.

For maximum contrast though, would a san mai billet be preferable?
 
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usually I stop around 400 grit but 600 grit is ok to but not over, going any higher is actually counter productive if etching.
 
I will freely admit that I don't know much about this but if I understand correctly there my be some steels that will etch darker. I think that a higher manganese content is one thing that could help. Like the 1084/15n20 Damascus. I believe that 80crv2 and Cruforgev will also go pretty dark. Some if the other guys here could probably recommend something that would give you more contrast that is available to you in Europe.

I'm probably telling you something that you are well aware of. Oh well
 
Stromberg Knives said:
Would it make a difference how high grit you sand it to before etching? Is there a best practice?
Click to expand...

Not sure if there's a best practice, but I'm remembering that on the last san mai billet I did, I didn't get a great contrast until I sanded to 1500g and then did a coffee etch after the FeCl. I rationalized that the 15N20 needed to get to a higher polish to prevent any etching.
 
Thanks for all the help guys.

Just to be sure, I res-sanded the piece to 400 grit and cleaned it thoroughly before giving it a new etch in a fresh batch of FC/destilled water. I neutralized in water with baking soda. This seem to have solved the problem with the greyish color, but there's still no contrast which means the 15N20 didn't resist the etch at all.

According to the ways of Occam my conclusion is that my 15N20 isn't up to par. Would you concur?

CX6PAko.jpg
 
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