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Knife Making Discussions A place to discuss issues related to all aspects of the custom knifemaking community. |
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#1
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Hammering and carbon content
I was looking at some knives on a website and this was from their description:
"The steel is compacted by the hammer, forcing a higher carbon concentration to the cutting edge. The actual crystalyn structure is tightened and more perfectly aligned, resulting in a more durable, longer lasting, finer keen edge." I am curious as to the truth of this statement. I have heard and read so many different things about steel over the years and I thought that I understood it but every once and a while I find something that makes me wonder. I was under the impression that the heat treatment governed the crystalline structure and the placement of carbon molecules for the most part. This quote is from a website and store that has an onsite blacksmith and sells many different smith's work so it seems credible. I don't mean to offend anyone who is involved with this website or store but I am curious about this statement's veracity. Thank you for your time William Conn Last edited by Hotnapalmdeath; 02-23-2012 at 04:11 AM. |
#2
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There are several statements there that are incorrect. It sounds to be written by someone other than their bladesmith who has misinterpretted what he/she was told.
Makes you a little leery about their product doesn't it. Gary __________________ Gary ABS,CKCA, ABKA,KGA |
#3
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I have been told the same thing - and believed it religeously until fairly recently. The idea of "edge packing" "aus - forging" and such has been around for over a hundred years. I can't say if it's true or not, but it's a hot topic of discussion among knife makers (recently on this very forum...). I keep an open mind - or better, I choose to remain sitting on the fence... In the mean time I keep banging steel, only because it's fun
__________________ Chris K. Two Mountains Forge Delta, BC, Canada www.twomountainsforge.com |
#4
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Hotnapalmdeath....Until recently, I was under the impression that forging was beneficial in reducing and controlling the grain size. After a lengthy discussion with WBE, and some experimentation on my part, I was convinced that grain size and growth are much better controlled through heat treatment than by forging.
However, having said that, I continue to believe that there is some benefit to be derived from impact forging...particularly in the grain alignment within the steel. The longitudinal alignment of the grain structure of the steel due to impact forging is at least one major benefit from forging which contributes to greater strength. It is possible there could be other benefits as well, but not being a metallurgist, I am uncertain of such claims, and would appreciate additional input from others such as Mete or kevin if you're listening. There has to be some benefit from forging steel, else the practice would have been long since abandoned....yet heavy industry, and a great many bladesmiths continue the practice. I am sure that there is more to forging than just the sheer enjoyment of beating the hell out of a piece of steel on an anvil. Last edited by Ed Tipton; 03-09-2012 at 09:06 AM. |
#5
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I will take this in two parts. First is the claim that hammering will concentrate carbon in the cutting edge. There is no mechanism that I have ever heard of that will move carbon in this way. Carbon can diffuse through iron crystals but this requires heat. You can't squeeze it through like juice through orange pulp. Then there is the problem of how the carbon supposedly collects. If it were forced into the iron crystal matrix it might cause imbrittlement, but that can't happen. If it was forced onto an iron atoms to form carbides it might cause imbrittlement, but it can't happen. If the carbon was forced to clump together to from graphite it would weaken the blade, but it can't happen. In short, it can't happen.
Second is changing the grain alignment in the steel. This can happen. It's called work hardening. Way back in the day, we're talking migration era and before, work hardening was used to harden blades. Basically it was a hold over from bronze blades which have to be hardened in this manner. Some of the older steels were too low in carbon to quench harden to any degree. Some were just too shallow hardening to quench harden easily. Some of it could be that quench hardening was known but tempering hadn't been figured out yet so quench hardening wasn't reliable. The down side is that work hardening will only give hardness in the low 50's HRc. Quench hardening followed by a proper tempering is a much better way of getting a hard edge on a cutting instrument. Edge packing is one of those theories that just won't go away. Some of it is the fault of the web. All sorts of garbage gets put out there without any peer review and it's stuck in the electronic record. Some of this even happens with books. The publications exist long after their content has been disproven. Doug __________________ If you're not making mistakes then you're not trying hard enough |
#6
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Nice view from my fence here...
Doug, Ed, this is great discussion material for newbies like me who don't know much about metallurgy. Both arguments sound plausible, the former much more "romantic". i can just see the blackened, sweaty face of the old blade smith by the shine of the fire impressing on his apprentice that "you must pack the steel with the blows of your hammer..." __________________ Chris K. Two Mountains Forge Delta, BC, Canada www.twomountainsforge.com |
#7
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Doug...OK.....I guess maybe I'm just on the dense side but....there is just something here that I'm missing out on.
I think I've got a handle on the whole quenching and tempering thing (at least for my purposes) but I still have this nagging question about forging.....and either I am getting the answer and just don't realize it, or I am not getting my answer. I do forge my blades, and I feel that I do a reasonably good job at forging them, but lately I'm beginning to wonder why I'm doing it....except that like most guys, I do enjoy just banging iron. We've pretty well established that forging does little to contol grain growth and size, and I guess it does contribute to longitudinal alignment of the grain within the steel for whatever that might be worth. Now then....ARE THERE ANY OTHER BENEFITS TO FORGING, AND IF SO, WHAT ARE THEY???? This whole discussion between forging and HT has become so muddled and confusing....and there is so much contradictory info out there that it's really hard to get the straight info. I've tried reading the HT and metallurgical books and manuals and I simply don't have the background to understand what I'm reading. I end up with more questions than when I started. What I need is for someone who really understands this stuff to explain it to me in laymans terms that I can understand....and I know I'm not by myself on this. Anyone care to take this on? |
#8
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so far i have been lucky heat treating but i know i'm probably not doing it right. for one thing i don't have a heat treating oven and just use a magnet to tell me when to quench,and i have no way to tell me how hard the blade is but they hold a edge great and they are not hard to sharpen. it seems like every site i go on it's different and that makes it even more confusing. |
#9
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I'm gona throw my $.02 in here as well. I have done ALOT of research on this very subject in the last few months.
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I had a whole paragraph written for this , then I chickened out The one thing that forging does.....it uses less steel. By forging your steel ends up in the knife , instead of on the floor under the grinder. You can only get so much steel in a 4" hunter , wether you forge it or stock remove it. The key to knifemaking is the heat treatment of the steel , from the mail box to the customer. It starts with annealing , then normalizing , then quenching , then tempering. Sometimes multiple cycles of each step is needed in heat treatment. I'm going to quit before I get in trouble. Dwane |
#10
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'Edge packing' I do feel stems from the hamon cult. I could be grossly wrong to but this is just my guess. With Hamon we can clearly see difference in grain structure due to heat treatment and it gets misunderstood to edge packing because they can clearly see a difference in the edge. __________________ Gold is for the mistress - silver for the maid Copper for the craftsman cunning in his trade. "Good!" said the Baron, sitting in his hall But steel - cold steel is master of them all. Rudyard Kipling (1865 - 1936) |
#11
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Grain direction cannot be changed by forging, but you can change the direction of the steel bar itself. Grain direction is set at the mill when hot rolled from the pour. If grain direction was changable by hammering, think of what you would have after forging a blade. If one edge packs hot, the grains are broken into smaller various different sizes, but are still going in the same direction. The achieved grain size reduction is negated when the piece is re-heated in normalizing. When the steel is heated, the larger grains "eat" the smaller ones. When heated 50? to 100? above the target austenitization heat, the grains will enlarge, but become uniform in size with a short soak. From that point, proper heat cycling will reduce the grain size to the desired level. If you edge pack with a black heat, you just add a lot of unnecessary stresses, and open the possibility of micro cracking. Neither method has any benefit what so ever in the end result. There are only two reasons to forge a blade. One is to get a shape that is impracticable to get by grinding or other means. The other reason is just because that is how you want to do it. The only way to control grain size is through heat, and it is physically impossible to compact steel. Pardon the pun, but a forged blade has no edge over a stock removal blade, assuming both are equal in all other aspects.
Last edited by WBE; 06-12-2012 at 07:35 AM. |
Tags |
anvil, back, beginning, blade, edge, forge, forging, grinding, hammer, hamon, handle, hunter, iron, knife, knifemaking, knives, material, steel, throw |
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