First laminated steel - the search for the lost core

[Stromberg Knives]

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.

Interesting, I might try this to cover all bases.

 

[JTknives]

It’s not the grit finish that resists the etch it’s the nickel in the 15n20 that does that. If I was a betting man I would bet you dollars to donuts that your “15n20” does not have much if any nickel in it. I don’t remember if you said where you got it from? If you need true uddaholm 15n20 let me know, we sell a crap ton of it to smiths. How I etch, take up to 400 grit and etch. I etch till the entire surface is dark black. Then pull the blade and squirt with windex and gently scrub down with fine steel wool. This will remove all the black oxides. Then I repeat the etch agian and scrub. I keep doing this till I get the contrast I want and depth of etch. Then it gets an instant coffee soak. I’m not sure how it works on San-Mia but on Damascus it really makes the dark layers pop. I then lightly sand over the entire blade with a fine grit paper to shine back up the high layers.

 

[weo]

It’s not the grit finish that resists the etch it’s the nickel in the 15n20 that does that.

Yes, the nickle resists the etch, I'm sorry if what I wrote implied otherwise. Where I was going was that a rougher finish can trap (is this the right word?) oxides and make the blade look dirty?

800g

1500g

 

[allenkey]

I've had .095" 15N20 from USA knifemaker that I could turn black with lemon juice. Always thought that was odd. It was incredibly easy to drill, also. Then I bought some from AKS and I've been wondering ever since if it was 15N20 at all that I had before. The bar I got from AKS was much brighter and way, way harder to drill lol

I can't help but I thought I'd throw that in there. JT's words have me wondering all over again lol

 

[Knight Owl Forge]

One thing I've learned working with 15n20 and another steel is how well you thermal cycled them will have a huge impact on final contrast. If you say grossly overheat the billet and grow the grain size, you won't get as contrasting of an etch if you had done everything correctly. Grain size, carbon migration, and many other factors come into play here. Ever see a damascus or san mai billet that looks grainy and diffused? The heat treatment was likely not done properly. This is also true when it comes to hamons... If the heat treatment was botched, the hamon will come out diffused or grainy looking. That messes with the contrast a bit.

 

[Stacy E. Apelt - Bladesmith]

One experiment you could easily try is to take a piece of each steel, harden it, sand it to 400 , and etch it. This should show you what the contrast will be in a san-mai of those metals.

This is what I get when I etch the core to check for straightness and proper centering:

 

[Stromberg Knives]

One thing I've learned working with 15n20 and another steel is how well you thermal cycled them will have a huge impact on final contrast. If you say grossly overheat the billet and grow the grain size, you won't get as contrasting of an etch if you had done everything correctly. Grain size, carbon migration, and many other factors come into play here. Ever see a damascus or san mai billet that looks grainy and diffused? The heat treatment was likely not done properly. This is also true when it comes to hamons... If the heat treatment was botched, the hamon will come out diffused or grainy looking. That messes with the contrast a bit.

You might be onto something here, since I'm a complete beginner at forging.

Could I have messed up the normalizing and grain refinement, which I did in the forge before I austenized in my kiln? I measure the temps in the forge with an Omega XL thermocouple probe.

How would you do the normalizing and grain refinement for 1095/15N20? I would like to use my kiln for all the operations where it makes sense, since it's temperature controlled.

 

[samuraistuart]

Use your kiln for normalizing and thermal cycling.
Normalize temp by the book for 1095 is 1600F, equalize, air cool. 1600°F-1650°F OK.
Thermal cycle: 1500F, equalize, air cool, 3 times (you can also do descending heats, as in 1500F, 1475F, 1450F) Usually 3 cycles is good enough. Just remember that excessive thermal cycling lowers the hardenability of a steel, and 1095 is already shallow hardening. I like to stay above 1414°F (and well above 1350°F) for thermal cycles, preferably ~1450°F-1500°F. Below 1350°F is spheroidizing temps; 1350°F-1414°F is where the austenite phase transformation is started, but not complete; "critical temp" of the steel is where thermal cycling for grain refinement is best done; thermal cycling above critical is fine as long as the temp is low enough close to critical; and cycling above ~1525°F-1550°F gets into normalizing (grain growth) temps again.

For all hypereutectoid steels during normalizing, cycling, and hardening, I employ a soak of 10 minutes rather than simply "equalize". Some do, some don't. For such a low alloy steel like 1095, it probably isn't as critical as soaking steels higher in alloy like O1 or 52100.

 

[weo]

One thing I've learned working with 15n20 and another steel is how well you thermal cycled them will have a huge impact on final contrast. If you say grossly overheat the billet and grow the grain size, you won't get as contrasting of an etch if you had done everything correctly. Grain size, carbon migration, and many other factors come into play here. Ever see a damascus or san mai billet that looks grainy and diffused? The heat treatment was likely not done properly. This is also true when it comes to hamons... If the heat treatment was botched, the hamon will come out diffused or grainy looking. That messes with the contrast a bit.

This makes much more sense than my line of thought....

 

[Ken H>]

One experiment you could easily try is to take a piece of each steel, harden it, sand it to 400 , and etch it. This should show you what the contrast will be in a san-mai of those metals.

This is what I get when I etch the core to check for straightness and proper centering:

Stacy - that is one pretty billet. Core is perfectly centered for full length. Good job! BUT - good job seems to come naturally for you {g}

 

[Stacy E. Apelt - Bladesmith]

Thanks, but I can't take all the credit on that blade. I started with a piece of Dictum's laminated steel. The billet has eight layers of contrasting softer steel on each side ( suminagashi) of a Hitachi white steel edge core (Shirogami #2), and a soft iron spine core. All together that is called suminagashi hon san mai kitae. This billet arrangement is very close to how a traditional Japanese blade was made.

During forging, I regularly hit the edge and spine on the grinder and dunk in the FC tank. This lets me know where to forge more and where to forge less … so the edge stays centered.

Here are shots of the partially rough forged blade that the edge shot was taken on, the starter billet, the forged out blade dipped in FC after a quick cleanup on the grinder ( but not finished), and ground clean (but not dipped in FC). I added an image of how the billet is set up.

This steel is so reasonable, I buy it in large batches from Dictum to forge tanto/wakizashi from. It costs about $40 USD for a 15" X 1.4"bar. Youi can forge a full size tanto or a short wakizashi from one. Some of their blade steels come in one meter lengths. They also sell plain white and blue paper steel as well as plain shirogami.

https://www.dictum.com/en/steel-cca/japanese-multi-layered-steel-core-layer-white-paper-steel-719617

 

[Stromberg Knives]

Thanks guys for all the knowledge sharing, I truly appreciate it!

Progress update. I started a new billet with the same setup as the previous one (15N20, 3.0mm, 1/8" as cladding with 1095, 3.5mm, 9/64") as core). It seem to have forge welded just as well as the last one. I then drew it out with the power hammer.

This time though, I did the normalizing and thermal cycling in my kiln, in accordance with your suggestions in this thread. I also did a sub critical anneal to prepare it for drilling and such.

I then ground away the welds and dipped it in FeCl, and this is the result. I consider this somewhat of a success since I managed to get some contrast between the two types of steel - but isn't it inverted? I'm absolutely sure I put the 1095 as the core (according to the poorly marked steels from the supplier, and this is also evident since I used twice as much 15N20).

Did I manage to screw something up again, or could the steels be marked incorrectly?

I'm pretty happy with the centering of the core, but I think I will use a thinner stock for it in the future.

 

[Stacy E. Apelt - Bladesmith]

Something is wrong with your steel labeling. That shows the nickel bearing steel in the center and the carbon steel on the outsides. The thin gray stripe around the edges is the decarb layer that needs to be ground off. This is where a surface grinder is a great tool to have.

 

[Stromberg Knives]

Something is wrong with your steel labeling. That shows the nickel bearing steel in the center and the carbon steel on the outsides. The thin gray stripe around the edges is the decarb layer that needs to be ground off. This is where a surface grinder is a great tool to have.

Thanks, I have ordered new bars of 1095 and 15N20 from a different supplier.

 

[Stromberg Knives]

I received the new steel, a couple of bars of 15N20 and 1095 from an other supplier. These were also adequately marked.

So I gave it another shot. I made a new billet with 15N20 cladding and 1095 as core, forge welded and drew it out. No hiccups so far. Then I normalized, thermal cycled and annealed it in my kiln. After that I made a knife which I then meticulously cleaned and dipped in FeCl, scrubbed with steel wool and dipped again, for a couple of times.

I'm pretty happy with the results, it worked a lot better than with the previous steel, but I still think the contrast is a bit low. I don't know if I could improve my process further, or if I have to go for stainless for a better contrast?

Here's a picture of the finished knife.

 

[weo]

but I still think the contrast is a bit low.

Have you tried finishing with coffee yet?

 

[Stromberg Knives]

Have you tried finishing with coffee yet?

Not yet, I was contemplating to try that.

Is it like FeCl where the 15N20 will resist the etch and the 1095 will get darker?

 

[Stromberg Knives]

Well I ordered some 420 for making san mai. We'll see how it turns out, like the famous quote... "anyone who has never made a mistake has never tried anything new".

 

[A.McPherson]

Thats a good lookin’ knife there Stromberg

 

[weo]

Is it like FeCl where the 15N20 will resist the etch and the 1095 will get darker?

I think this is more a staining thing and not an actual etch, but I hope those with more knowledge will chime in.
In my experience, no. If left in long enough, both will darken. What I have done when this happens, is to just clean the blade and re-do.
Here's what's been discussed in the past: https://www.bladeforums.com/threads/coffee-etch-clarification.1627024/#post-18638790