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Alright so there has been a lot of trial and error going on in my shop. Been making San-mai and Gomai gyuotos. Profiling and geometries have been giving me problems but I think I have it nailed with this next one...if it survives. I have been finding it much harder to avoid Delams in the quench of these types of constructions, versus a regular damascus blade. I assume this is due to the lack of stretching of this type vs the wester pattern welding since the welds get stronger the further the welds are stretched. That's my observation any way.

 

This one has a blade length of 11" and 2" wide at the heel. It is 5 layers of 1018/15n20/W2/15n20/1018. Not HT'd yet. Just felt better about this one after 4 prototypes.

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Here was the last gomai I did last week. I for some reason ground at the wrong angle. 3 degrees on each side is a little steep I believe for a 1084 steel. It is why the lines are riding so high. Also not sure why my phone is posting pics upside down.

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Edited by Daniel Cauble
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W2 is so damn easy to overheat and crack when thin.

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Oh wow, what were you doing when it did that? Quench?
I really like the pattern in the upside down one, I might have to give five layers a try some day

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That I have learned (Its happened more than this time) that when overheated, the W2 (Or any hardenable steel really) instead of wanting to crack along the edges and up towards the spine, perpendicular to the blade it relieves itself down the length of the W2. I suspect this is due to the mild jacket steel being malleable and not wanting to crack for the W2. So it relieves the stress somewhere. That somewhere is lengthwise down the blade.

 

Sad day, but honestly I already have another billet ready to go and forge into the next attempt. Plenty of W2, 15n20, and 1018 at my disposal. This will just be Gyuto #5 that didnt work out in the past few weeks. This being the first over heated one though.

 

Btw, you can hear this cracking if you listen carefully.

 

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you might want to try some clay on thin blades - acts as a heat sink to prevent the blade coming up too fast and over shooting critical, and also should help confine martensite transformation to the exposed edge where it has room to do it's thing as opposed to the stresses of expansion/contraction taking place inside the mild steel jacket...

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Not that I've had any delaminations as spectacular as this (and it is spectacular. That's one I'd almost be proud to hang on the "wall of shame"), but one thing that I've found helps a lot is to soak the billet at welding heat for 5-10 minutes after setting each weld. The operating theory is that the grain colony growth across the weld boundary helps to stabilize things.

 

That being said, the phenomenon is eating at my brain, so I'm going to ask some questions if you don't mind.

 

  • Is that a weld delamination, or is it the W2 core splitting?
  • How many normalizing heats, at what temps did you run before quench?
  • What are you using as a quenchant?
  • Are you heating in a forge or a kiln?
  • If in the forge, do you have a thermocouple to monitor forge temps?
  • Do you have any close-up pictures of the failure zone? What does the grain look like in there?

I'd love to figure out what's going on here. There has to be a way to control it...

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Thanks Jake. I have thought about that from reading other threads in the past, but then I am reminded of the Japanese doing these builds, and not differentially HT. Usually kitchen knives, especially chef knives are made to be hardened all the way through. While some of my past examples have a little bit of spring to them with the aid of the jacket, they are still hardened through and relatively stiff. Now the likes of Kiyoshi Kato have had decades to hone their abilities and probably far more failures before they got it right...I kind of want to be that good. Not even kind of, I don't stop thinking about it. Ever. An obsession that I hope leads to success.

 

Then again if a few more fail before I can get one the way I want it, I may have to give that idea a shot any way.

 

deker;

 

*The split is the W2 core splitting. All laminations are intact

*3 normalizing cycles. The grain is relatively even, with the edges just slightly larger than the center, due to what I suspect was rapid heat up on my part. A mistake brought about due to the length of this blade (11.5" edge length) and the limited heat zone I can create with my coal forge. The temps are as close to transformation as possible. I do not have a thermocouple...yet.

*160F Canola Oil. Usually deep hardening steels I heat it to 130F. In this case the W2 is shallow, and I wanted it to get as hard as possible in oil, so I lowered the viscosity by heating it up higher.

*Heating in a coal forge.

*No thermo, just my eyes watching the shadows disappear at transformation. My overheating from that point was due to me attempting a soak to allow carbides to be in solution. This resulted in a higher than projected temp.

*I can take close-ups later this weekend. Extremely busy weekend.

 

From what I understand here is the W2 was overheated. If it was a monosteel W2 blade it would have cracked like normal. Instead the forge welds of the 1018 held strong and forced it to crack the W2 in half length wise.

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Hi so can anyone explain the difference between San Mai and go mai please. I would really appreciate it. 

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1 hour ago, Paul Checa said:

Hi so can anyone explain the difference between San Mai and go mai please. I would really appreciate it. 

 

san mai = 3 layers, go mai = 5 layers

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Thanks! And so what's it called when it's layers of the same kind of metal? I saw it in forged in fire but I can't remember what they called it... 

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A disqualification if I remember correctly. :ph34r::D

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"San" in Japanese is "3."  "Go" is "5."

 

Shino-Japanese 1 to 10:

 

Ichi - 1

Ni - 2

San - 3

Shi - 4

Go - 5

Roku - 6

Shichi - 7

Hachi - 8

Ku - 9

Juu - 10

 

"Mai" is Japanese for "sheet."  In terms of knife making or billet making, we'd probably translate it more as "layer."  But, more or less the same thing.

 

So, "San-mai" is "3 sheet", "Go-mai" is "5 sheet", etc.

 

 

 

 

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17 hours ago, Dane Lance said:

"San" in Japanese is "3."  "Go" is "5."

 

Shino-Japanese 1 to 10:

 

Ichi - 1

Ni - 2

San - 3

Shi - 4

Go - 5

Roku - 6

Shichi - 7

Hachi - 8

Ku - 9

Juu - 10

 

"Mai" is Japanese for "sheet."  In terms of knife making or billet making, we'd probably translate it more as "layer."  But, more or less the same thing.

 

So, "San-mai" is "3 sheet", "Go-mai" is "5 sheet", etc.

 

 

 

 

thanks!!

 

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On 10/29/2019 at 4:34 PM, Alex Middleton said:

A disqualification if I remember correctly. :ph34r::D

hahahaah nice one but no, was it hatta?  when you layer the same steel over itself so as to make it stronger? correct me if im wrong i just remeber. 

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1 hour ago, Paul Checa said:

hatta

 

The term there was "hada," Japanese for the pattern in tamahagane (and multifolded monosteel) blades.  As in, if the pattern that shows in the final polish looks like wood grain, that's mokume hada.  So they weren't even using it correctly.  Big surprise there! :lol:

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Ahhhh maybe I heard it wrong. That was probably it. Doug marcaida's accent threw me off... So now that we know what we are talking about Alan (always to the rescue) could you enlighten me as to what the benefits of hada are? Is it true it makes stronger steel? 

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The Japanese smiths using tamahagane folded it for a couple of reasons.

The material is slaggy, folding it refines the material (like running through a rolling mill) and drives out slag.

The tamahagne has wildly varying levels of carbon.  The smith would use some high carbon and mix that with low carbon to get about .60 carbon at the end (1060-1075 in modern terms)

They did both of these things by folding and welding the tamahagane.  Because there isn't much difference between the high and low carbon areas, like an addition of nickel, there isn't much contrast, but there is pattern.  This is what they call hada.  In the polish the polisher makes decisions that either bring out the hada, or not.  It has no effect on the strength of the steel, it's part of the aesthetic process.

 

You could get hada by welding mild and 1095, it's very subtle and ghosty.

 

Geoff 

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Just to add to Geoff's comments:  Nothing good can come from welding the same material to itself with modern alloys, as far as mechanical properties goes.  If you weld 2 dissimilar materials then you can get a blend of the properties.  Forge welds are a source of potential flaws.  When dealing with bloomery steel, weld flaws are much less likely to be a problem than the slag that is definitely a problem.  Modern alloys don't have these slag inclusions in them, so you have no benefit to working the metal.  The only benefit most modern forge welded materials present is aesthetics; which is important (ish), but not structural.  

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Carbon loss can show up in folded modern monosteel, more folding with slightly changing atmosphere and forging as well as carbon migration can compound to show variations in the steel. While it might seem like it would be too subtle to see a pattern it can be quite visible. You can certainly see carbon loss in one blade I made that was 5 layers which were quickly forged into a blade.

 

two piles of dirt may look exactly the same, but up close/side-by-side you will notice the difference. 

 

there are a number of steels that won't weld to themselves. But then there are things like welded cable that are all one steel (sometimes, some could be several steels) but show a pattern.

 

i wonder if a manipulated laminate (laddered, raindrop, twisted, ground random) has a more disturbed flow of stress which could make it resist shock from quenching better. I suppose it takes so little movement in a blade to crack it though.

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now you make me wonder, is there a way to introduce more carbon into the steel while forging... hmmm... just a thought, im a beginner, thats why all the questions, its probably best to just do all the carbon introducing in the foundry and let it be born with it right? still so much to learn... i love this forum... theres so little knowledge in mexico thanks for all this guys, its great to have you as teachers.... 

 

so one more question... too much exposure of the steel to the forge heat is bad for the steel right? as in when im forging my billet into shape i shouldnt leave it in there too long after it has achieved a nice orange color, i have to take it out hit it and put it back in and so forth right? we dont want it to sit in the forge for too long... 

 

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Correct, long times at elevated temperatures will both result in grain growth (which can be reversed by proper heat treatment cycles) and decarborization (which is not reversible, but starts at the surface exposed to an oxidizing atmosphere and progresses inward with time). Actually I suppose that you can theoretically reverse decarborization by soaking the stock in a carbon rich atmosphere over a long time period at elevated temperatures, but I don't know of anyone who bothers with this.

Edited by Dan Hertzson
clarification

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yeah, just had a flashback to a dagger i made, had the appearance of sugar crystals when it broke. hahaha thanks dan... 

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