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Simon Attwood

Unusual O1 grain

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OK . I had a little accident with my "mushybushy" while making a sheath .. the sheath must have still been slightly damp and I rather stupidly left the blade in over night ...... so had some nice rust next day which meant I needed to repolish ...... now i have got something very unusual

 

The Steel is O1, Clay hardened, polished  and etched with soapy vinegar and finally extra fine pumice ...... on close inspection of the bevel ..... a rather unusual grain has appeared ... has anyone had a similar experience with O1, or other steels? ... or an explanation?

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Two questions, first - I assume you mean the white blotchy lookin' things, yes?

 

and second- did you watch quench it?

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Hi Brett,

 

No I don't mean the blotches .. i mean the fine wavy lines on the edge

 

Yes I did water quench followed by oil

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Guest Jason Dingledine
OK . I had a little accident with my "mushybushy" while making a sheath .. the sheath must have still been slightly damp and I rather stupidly left the blade in over night ...... so had some nice rust next day which meant I needed to repolish ...... now i have got something very unusual

 

The Steel is O1, Clay hardened, polished  and etched with soapy vinegar and finally extra fine pumice ...... on close inspection of the bevel ..... a rather unusual grain has appeared ... has anyone had a similar experience with O1, or other steels? ... or an explanation?

Best Guess from the pics is that it is alloy banding.  What kinds of thermal treatments did you do to the blade prior to quenching??

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I'm with Jason...I think it is alloy banding. I have seen some O1 make some weird patterns when cycled multiple times to normalize but *NoThinInG* like this!!

 

Or, it may be a surface phenomenon caused by the rusting before you etched and finished. Rusting will do some strange things. I have not seen patterns like this but I have seen rust bring up some stuff in the steel that I didn't realize was there.

One time, I polished a rusted bar of steel that had been stamped with my initials before (it was an old chisel) it was turned into a knife. The rust made the initials come back as a shadow after etching and polishing.

 

I don't know, 'Mushi.

 

Maybe it's a sacred blade and this is a sign to join a monastary or something.  Super  Brother 'Mushi...now *thats* funny!  :laugh:

 

Brian

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I think Kevin Cashen playing around with some O-1 and prolonged temperatures got a "kinder-sorter" wootz pattern. Some kind of alloy segregation. Seen similiar in 52100.

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well it went through a kind of normalizing ... after forging and grinding  .. left it in the hot forge while the forge cooled ... takes 2+ hours to cool down inside... then it sat on a shelf for a week ......and then a couple of cycles prior to quenching.

 

I've heard of the alloy segregation, Al ... and seen some pictures, although not in the flesh so to speak ... and that has tended to look more orange peel effect ... as brian said ... nothing like this

 

but thank you for your thoughts Brother Brian, Brother Al and Brother Jason  ???

 

Brother Mushi :D

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I'd take no bets that it's alloy banding.  It can appear in lots of different steels.  It's a very easy process to reproduce and is no big secret, as Kevin and so many others have proven.  My first happy accident was big, bold on an old horseshoe rasp about fifteen years ago.  I think it should be something every bladesmith or knifemaker into heat treatment should know how to do.  In Mushi's case, I really like the subtlety.

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My bet is on banding.  Remember that as the steel cools in the ingot, the outside cools very quickly and then the cooling rate slows down.  Solid fingers begin to grow into the molten steel.  As this continues, the fingers are ejecting carbon and alloys, making them of lower carbon&alloy content compared to the liquid around them which is getting higher in carbon&alloy.  The result is a banded structure of pearlite and ferrite.  The ferrite is from the fingers and the pearlite is from the liquid around the fingers.  Banding is present in virtually every steel with enough alloy to segregate.  It is not a defect, just a fact of life.  Multiple heat cycling, like normalizing will reduce it some but not get rid of it.  Even when you have transformed the steel to martensite, the segregation pattern remians.  I kinda like the effect.

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Oh I wasn't compaining about it :D  .. i like it too ..... just wanted to know what I'd done ??? :;):

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I'm getting the same thing in W2 and I get it every time I forge a blade out of this batch of steel. I forge to shape normalize 3 times, heat treat, finish and do a light etch. It usually looks like high layer damascus. I've been wondering what it was, but I like it anyway.

 

Don Hanson

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I'd take no bets that it's alloy banding.  It can appear in lots of different steels.  It's a very easy process to reproduce and is no big secret, as Kevin and so many others have proven.  My first happy accident was big, bold on an old horseshoe rasp about fifteen years ago.  I think it should be something every bladesmith or knifemaker into heat treatment should know how to do.  In Mushi's case, I really like the subtlety.

O K Mike, you have sparked my interest, what am I doing to get this damascus look in W2. I gave a piece of this steel to a freind who forged a bowie out of it, finished it to 2000 grit, did a light etch and he got no layering or damascus look,He forges by hand and I use a 100 lb power hammer. Also before I heat treat I can do a light etch and I see the layering very clear.

 

Don

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There are a bunch factors.  One RK already mentioned, the cooling factor in the large billet at the mill.  There are going to be portions of the steel billet that have greater or lesser areas of dendritic or interdendritic formation as a result of the cooling rate of the liquidus/solidus due to the alloying elements while it's laying in the yard after initial formation.  So, it may be a batch difference.  Historically, the mills used to have soaking pits for the steel to cool in a controlled way to make more homogeneity in the batch that doesnt' happen now with continuous casting processes.  So unless we can find a mill that still soaks things we can't compare.  

 

The second is the alloy content, specifically manganese.  Mn promotes banded microstructures of ferrite and pearlite.  The more Mn (as in O-1), the more segregation, the more banding.  But, as RK points out, all steels have the microstructure present to some degree.  So cooling still has an effect.  

 

The difference between alloy rich vs. alloy lean regions has a very strong effect on the critical temperatures of those regions.  If you were able to control just getting over the critical temp of one region and avoid getting over the other you're going to affect the banding by promoting grain growth in one band and not the other.  The tungsten/vanadium variations in your W-2 are going to be of possibly greater effect here.  

 

Physical deformation also appears to have a huge effect. The more deformation, the finer the banding if the material is worked in parallel to the bands.  The more deformation the coarser the bands if the material is upset along the band lines.

 

The crude way to make banding is based on multiple cycles above and below critical.  At least that's how I got all the banding to show better when I did it.  Howard helped figure that out when it happened.  Lots of the cementite segregation stuff was figured out by Al Pendray and John Verhoeven when they worked out the wootz recipes.  

 

When I mean multiple cycles, I mean 15-20 times.  It seems to consistently reproduce itself when I take the time to work the material this way.  Kevin Cashen also worked out a method to control the temp above Acm but below A1 in 52100.  

 

Somewhere in the middle of your shop practice, as different from your buddy, within the above variables is the source.

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Thanks Mike and to everyone else here,This is a big help.

 

Don Hanson lll

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I need to revive this thread 'cause I have a few questions for guys who have been exploiting this "alloy banding" type of effect by using multiple normalization cycles.

 

Does more cycles always accentuate the pattern in most steels? What about low alloy stuff like 5160? I am starting to get some banding like this with 6 cycles of decreasing temperature and I'm wondering if I do like, 15 or 20 cycles (I'm using 5160) from 1550f down to say 1100f in 25 degree increments the pattern will be more pronounced.

 

Also, does this segregation of alloying elements compromise the ultimate integrity of the blade to a large degree? Does banding the various elements make the steel, in this case, *not* 5160 in some bands but "something else" because the microchemistry of the steel has been altered?

 

My mind is wandering with the possibilities of exploiting this phenomenon.

 

Thanks for the indulgence!

 

Brian

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Brian,  The difference can be quite significant so you do get two different alloys in one steel.  I think numerous normalizing cycles would actually tend to reduce the banding by allowing the carbon and alloys to diffuse into the low carbon areas.  This is driven by entropy which hates to have any variations in chemical distribution in an ordered system.  Normalize it enough (this may theoretically require infinite heatings) and you will completely homogenize it. BUT!....the idea of normalizing at a temperature just hot enough to austenitize the high carbon areas is interesting.  However, some of the low carbon area would be partially austenitized, too.  This should allow some of the higher carbon areas to donate carbon into the low carbon areas.  Hmmmm.  It still sounds like multiple heating would tend to homoginize it.    As far as compromising the integrity of the blade, I don't think so. Pattern welded damascus exhibits similar variations in chemistry with no harmful effects.

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I was thinking of it more in terms of carbide seeding. If you heat the steel to a high enough temp to put all the carbon into solution and then do subsequent reheatings dropping the temperature each time, the orginal carbide formed will act as seeds for the next thermal cycle. The more carbides that form the stronger the attraction so you get a lamelar structure and that is what's showing.

 

The process starts during the forging operation and if you are conscious of it and watch your heats you can get quite a few cycles prior to heat treating. The stronger the carbide formers the more pronounced the bands.

 

At least that's my intuitive sense of what's going on, I may be wrong.

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I think you're onto something Don.  When watching smiths from other cultures, one of the practices I noticed was multiple, relatively low temperature heats.

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