Just wanted to say that this is an interesting discussion and I hope it will continue as long as there is something to be learned from it. I know you guys (One and KC) don't see eye to eye much of the time, and I'll not say that there's anything wrong with that, just that I hope it dosen't put a stop to these discussions before they run their useful course. Feelings run strong sometimes, for me at least, but steel dosen't take account of them so when they enter these discussions it is usually not for the better.
Justin, as well as the standard civility policing, I feel my job here as moderator also includes seeing to it that the information you get is of reliable quality. Just as good science shouldn’t even deal with opinion or feelings but provide the most likely hypothesis, and eventually theory, based on the best available data, I want the information here to be easily separated from opinion. When it is hijacked by an agenda is when science does become the biased political tool that it is sometimes seen as. When I can’t have my information agenda free, I at least insist on having it easily separated from opinion, and that is the same courtesy that I am asking for you and the other visitors to this forum. And I feel that is part of my job here, a job that also benefits from separating feelings from it. Let some of my best buds post strong subjective feelings as absolute statements of fact and see if I perform my moderator obligations the same. I would.
To help with the discussion I will give some of my input and observations:
First there are points of agreement that are based on actual fact. No steel is perfect, the fact that every piece of steel has millions of defects in the atomic stacking is what allows us to forge it. On the atomic level is it riddled with vacancies, dislocations, and divergent stacking arrangements; grain boundaries themselves are deviations from a perfect crystalline lattice. On the macro level there are pipe, alloy segregations, slag inclusions etc… they are an inherent part of the material and we deal with them every day whether we know it or not. And this is on our end of the materials evolutionary path, the best it has ever been. The much touted steels of our ancestors were loaded with sulfur, phosphorus out of control deviations in carbon and inclusion levels that make our worst modern stock look pretty darn pure.
Consider this, if an alloy segregation line down the length of homogenous steel renders it so weak that we must walk on pins and needles while heat treating it, how totally useless is every damascus blade ever made? I have done extensive study in this area and after countless hours with damascus, from old swords to my own blades, under the microscope I can safely tell you that the steel pictured at the beginning of this thread is pretty homogenous in comparison. And yet I have found very little difference in most strength based properties, when it is done correctly.
Another point of agreement- forging will indeed help with segregation issues. But theories diverge on the exact cause and effect. I have found the hammer is a distraction from the real benefits of the multiple high temperature thermal cycles during the forging operation, which allow diffusion of the segregations. I base my theory on observations during testing which involved metallographically identifying the problem and then observing the same changes with several normalizing cycles alone. The mill reduced this steel stock from several feet to a fraction of an inch, our deformation is barely worth mention in comparison. But the mill limited the thermal treatments to the bare minimum, so we can easily exceed what they did with heat. You cannot drive alloy atoms through iron with a hammer, but with heat you can get them to simply move on their own.
As previously agreed, the steel supply is getting quirkier. One of the down sides to recycling is the amount of trace elements that are reintroduced to accumulate to levels that now approach alloying. This is probably a larger threat to proper heat treating than slag inclusions, which our ancestors dealt with wonderfully. With the allowable swing in numbers for each given alloy, it is really best to find a batch of steel that really works for you and buy as much of it as you can possibly afford. Getting your steels in small amounts at a time will have you constantly adjusting your heat treatment to match the newest unforeseen chemistry that gets thrown at you. This is not new and the bulk purchasing is how industry has also traditionally dealt with it, but with the looming threat of many simpler steels simply being “phased out” the idea of stockpiling a lifetime supply of good stuff becomes better all the time.
I hope some of this helps and that I have affectively provided input, based on my observations of the data, that can easily be separated from any of my personal feelings that may have crept in with it.