Originally posted by mete
...(Kevin you may use this thought in your classes) What makes ice cream texture so smooth ?? As the ice cream is frozen ( nucleating new grains ) we stir it (forge it) to permit many more points of nucleation therefore smaller grains and smoother texture....
That is good. I had not thought of that one.
Originally posted by rdangerer
...(Very interesting stuff Kevin. Please do come back to this forum and elaborate when you feel like you have validated and reproduced the results you are seeing. Sounds like one heckuva way to build a blade, big or hunting sized, for both toughness, AND good edge retention, with the beauty of damascus. And that is a tall order. I think a number of 'smiths would appreciate hearing your insights if you don't mind sharing.
I have no problem sharing, anybody who knows me is aware that I detest "secrets" and those who claim to have them, I just think it is silly. But something I detest even more is looking like a fool becuase I jumped to premature conclusions before validating preliminary findings.
I a study that I presented 2 weeks ago, at the Ashokan seminar, I observed phenomenon in many aspects of performance (heat treat-ability, material consistancy, edge retention, impact strength and interesting observances under the microscope) of many damascus combinations. I am one of the biggest sceptics around and have never thought of damascus as anything more than just another steel, that, if done right, could be as good as the steels used in it. But my initial results have me rethinking my entire view to the point that I need to do much more study before I will have the guts to admit everything I am seeing.
One thing that I am seeing enough to admit to is somethig that I had a hunch about all along. The so called "damascus cutting affect" appears to be a reality when cutting certain mediums, not due to the hard/soft layer nonsense, but instead how this material goes dull.
Even though I always knew O1/L6 was about the best choice I personally have made for combinations, it has blind-sided me with some behavioral characterstics that are just not normal (in a good way). I really want to get some sort of clue as to the mechanism for this behavior before I start speculating in front of the masses. I think there are already way too many wild@##$% conclusions jumped to in the knife business with total lack of solid evidence, without me adding to the confusion.
Mete: I have not done any serious studies involving bainite in my mixes, but I can guarantee that with all the hype these days, I will be doing such testing.
At this point I also find it hard to resist comments about nucleation and grain refinement by mechanical deformation, since I also have ahd a keen interest in that field as of late. The grain refinement by cold working does not result in breaking up or fracturing of grains, as mete pointed out any kind of fracturing is bad and requires welding heat to fix. What happens is the grains are elongated and deformed by slip within the crystaline lattice, inducing strain energy within the lattice and lots at the grain boundaries. This all still means nothing to grain size until the steel is reheated. Then at Ac1 all of that engergy will provide points for which new tiny grains to nucleate. After they form they will begin to grow by consuming the other grains. Large grains tend to grow at the expense of smaller ones. There are a couple of hitches to this whole hammer refining idea though-
First the residual strain will reduce the recrystalization temperature and increase the rate of grain growth. It is still heat and not the hammer that does the actual transformation, and when it comes to putting engergy into a blade, a forge fire will beat even the biggest hammers hands down. There is a critical amount of cold deformation required to create these points of nucelation and there is a phenomenon known as uneven coarsening or germination that can result by putting just enough strain in to start the ball rolling but not enough to do a thorough job. A few sacattered points of higher strain will result in a few rapidly forming grains that will begin to coarsen quicker as they feed off their finer and slower brothers. In light of this I personally don't get into hammering for a few minutes at teh end of the forging at dull red. but I do get into using heat to evenly refine the grain throughout. If points of high "stress" for nucleation is what you are looking for, no hammer ever made by man can put more stress into every grain of the steel like martensite. If you want to shrink grains real fast, reheat martensitic steel to Ac1.
I guess my point is, that I would shape the steel with a hammer and leave the internal structures for the fire and heat treatments.
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