Carbon Migration in Damascus

  • Thread starter Thread starter Ruppe
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Ruppe

I have seen recent posts on rec.knives that seem to indicate that carbon migration of older damascus lessens the differences between the steels used to the point of not being able to re etch to see the different layers if one has buffed away the patina. My own experience say that I can re etch to get back the difference. Is there really an incredible carbon exchange that goes on after forging that would make the two steels used, ie medium or low carbon and high carbon become the same after some moderate period of time, like say, less than 100 years?

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Ron Ruppé
http://www.ruppe.com
 
Ron; doesn't happen. Check this website for some notable Nihonto ('Samauri Swords'), and look at the first one. Still has the layers visible. It was made in AD 800!!
http://www.yesnet.or.jp/lucas/katana/JAN/main.html

If this piques your interest, here is the motherboard of Nihonto with a lot of links:

http://www.gemlink.com/~rstein/sites.htm

Enjoy. Walt
 
You are asking to differen questions.

1)Do you have carbon migration
2)Can you still see the layers

Answer to the first question is you have carbon migration, unless you have something that will stop migration in the layers and that something is pure nickel. So unless you have nickel there is carbon migration.

Now answer number 2 is it is still different metal so the layers will be there.

If you don't belive me look at a wire forged blade it is all the same stuff but you still have layers.
Tim Zowada has some good data on this subject
 
gregj62; Most interesting indeed. Could you do us the favor of quoting the websites of your sources? Thanks Walt
 
Walt Tim doesn't have the data on his site, I read it in the mag. he writes for. I e-mail him and asked him to stop by. If maybe a couple more asked him nicelt he would come.
smile.gif

http://www.unnet.com/homepages/tzowada/index.htm

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-Greg
 
Tim Zowanda has written several articles dealing with damascus that appeared in the knife rags in recent times. He disparaged the common 1018/O-1 mix has having too much migration during formation resulting in what he deemed as an unacceptable steel with poor RC capabilities.

As an aside, Guy Hielscher's damascus is made from 1018/O-1 but with different percentages and processing than the standard Tim referenced. As a result Guy's stuff yields an exceptional blade with a high and usable RC. I have one of Guy's knives and it is an exceptional performer.

But back to the thread, I've only read about carbon migration during the heating of metals used to make welded damascus. Never seen anything about migration as a feature of damascus steel aging.

I guess you could say, like Ron, I'm quite curious and would like to see more here so that I can gain an understanding of this phenomenom if it actually exists.



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-=[Bob]=-

Always yield to temptation as it may never pass your way again!
God save us from those who want to save us from ourselves.
Forgive your enemies....but not before they're hanged!
Rascality has limits; stupidity has none.

I did NOT escape from the institution! They gave me a day pass!





 
Well I don't think I made my self clear. You sure can tell I am not a writer by trade. No I don't think carbon migration get worst after it is forged, it only happens when forged. What I was trying to say(and not very good either)was that all of the carbon has already migrated when you forged it. If you check any damascus without nickel the carbon will be the same everywhere, So it couldn't get worst because all layers are the same already. And you still have the layers. The layer will be visable no matter what. It doesn't matter about the carbon migration.

I hope I made myself clearer. sorry
redface.gif


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-Greg

[This message has been edited by gregj62 (edited 30 January 1999).]
 
Are you saying that in the forging process there is an exact exchange of carbon molecules that averages the percentage of carbon between steel that originally had different amounts of carbon?

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Ron Ruppé
http://www.ruppe.com
 
Yes that's right. I have not don't it myself Just took a metal class in collage that is what they said, also have read it in a couple of books by knife makers and in the mag that Tim Zowada writes for.(heck I can't remember which one that is, I get them all)
ther are some blacksmiths that think that if you work real fast and don't use any more heat then you haft to that you can stop some of the migration. But I doubt if you can
smile.gif


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-Greg
 
To add some more data, I remember reading an article by I think Wayne Goddard, who said that carbon migration starts to occur after as little as X layers, where X is less than 500, and maybe less than 250 (can't remember the exact number, sorry).

Joe
jat@cup.hp.com
 
Yes Joe I kind of remeber that also, but some think it does it no matter what. I wish I could get a few blacksmiths to visit this fourm.
smile.gif
they would be alot of help.

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-Greg

[This message has been edited by gregj62 (edited 30 January 1999).]
 
I now see the confusion. The original question was does carbon migration occur AFTER forging, to such an extent it tends to significantly change the carbon content of adjacent layers. I do not believe this to be the case, and cited sources to prove this.

Greg was talking about carbon migration DURING forging. This has been known to occur, for about 1200 years. Japanese swordsmiths wrapped the steel in rice straw and clay if the carbon level in the steel got too low. Carbon would migrate from the rice straw back into the steel. See the above web pages I quoted for more information on this. Walt
 
Here is the e-mail I got back from Tim Zowada
He said he tryed to get on but the forum was down. he had to pick that time.
wink.gif


Greg,

Thank you for being interested in my opinion. I tried to go to the forum but
it was down. You might want to check out the forum on delphi.com Don Fogg set
it up and it is pretty good.

Carbon migration does happen. You can stop it, if you want, by having a alloy
of at least 7% nickel in the way. Once the steel is heated above 1320F the
carbon begins to go in to solution. The hotter the temperature the faster the
carbon will move around.

Overall, carbon migration is a good thing. It allows all of the layers to get
hard. This makes a huge difference in edge holding. If you work your
percentages right you can easily make Damascus that will harden to 64HRC and
have at least 0.8% carbon.

To see how quickly it can happen just look up the case hardening formulas in
the Machinists Handbook. Even if you could magically avoid the migration that
occurs during welding, you would get 100% migration during the short time it
takes to forge your blade to shape.

I hope this helps.

Tim Zowada
http://www.unnet.com/homepages/tzowada/index.htm
Click to expand...



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-Greg Johnson
ICQ#4236341


[This message has been edited by gregj62 (edited 03 February 1999).]
 
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