|
me2
Starting Member
10 Posts |
 Posted - 03/31/2008 : 20:51:11
|
Since it felt so good to rant in the other thread, I thought I'd do it here as well. This one is much more general, so I put it in the general forum. Here goes.
Why do people who want to market their knives as tough use steels that dont stand a chance from the beginning? For cryin out loud, there is a whole series of tool steels dedicated to toughness. Has anyone read the Verhoeven on-line blade smiths and heat treaters book? If so you'll know the diagram I reference. Its the one showing the decrease in toughness from 1040 to 1050 steel. The hump goes nearly flat. Can you imagine what the hump looks like when you double the amount of carbon? Like plate glass. These higher carbon steels dont even show a hump (or toughness peak) on the same test; a different one is used. Another thing that irritates me to the point of wanting to punch babies is that a lot of people assume that softer equals tougher. Thats clearly not the case. Just look at the above referenced diagram to see proof. Peak toughness for the higher hardness is at ~400 degrees F. Of course this is different for different steels, but do a little digging before selecting one and trying to claim its tough. There are literally libraries of steel information, and I'm not talking about metallurgy or theory, just published data with numbers that say with this treatment, this happens; if you dont know why, there is a whole other library for that.
Look at Noss' tests. Most knives with ratings of 4 or higher have carbon contents of 0.8% or less, or are laminated for the express purpose of increasing toughness, ie the A1. Can higher carbon steels be tough? Sure, but you have to draw the hardness down, loosing edge holding ability in the process. Dont forget that trough that happens just after the toughness peak, and if it applies to the chosen steel, avoid it. Just dont expect to win any edge holding contests, even with the super wear resistant steels. I must say that I find it telling that the highest rated knife so far has a carbon content of less than 0.55%
To further complicate matters, a certain degree of hardness is required, otherwise tough knives could be 1018 steel. Its a balancing act, one that has a pile of poor souls under the tight rope.
Does anyone know where to get 4340 or 4140 in plate sizes of 3/8" or less? This seems like a good candidate for a tough knife, with a hardness of about 56-57. S7, S5, L6, A8, H13, 5160, 6150, 9260, 1040, 1050, 1060, 8670, 4340, 4140, 1080, 1075, 12C27, 12C27M, Aus-4, Aus-6; all these are very tough, but get almost no press for it, with few exceptions, like L6, S7 and 5160. There are 20 steels listed there, just pick one. And yes, there is a loss of toughness when choosing a stainless over one of the others, but for the stainless steels listed above, the difference is pretty minor. Also notice the highest carbon content is around 0.8%, although I'm not completely sure of the stainless steels. For some real fun with you steel junkies, try some bainitic 01, 52100, L6, 50100, 1095, or 07, if you can find it.
I'll answer my own question from above. I think there is a tendency to pick steel first, then try for attributes after. If the primary purpose of the knife is to be tough, not break, and not bend to the point of uselessness, then pick the steel accordingly. Dont use a steel that has been reported to chip during sharpening, such as S30V. As has been said before, pick the right tool for the right job, and part of this is making the tool from the proper material.
Man, I havent felt this free since the first time climbing without a harness.
|
|
A Steel Rant
Forum Locked
Posted - 04/07/2008 : 02:05:49
