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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making. |
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#1
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Re tempering?????
I use forged 52100E and have no power hammer , Usually use about 4" of 1" bar to start , What im gettin at is a considerable amount of work. recently I Tripple hardened per Mr. Fowlers prescription & usually get a beautiful temper line , This time I lost the line & hardened the whole blade. THe questions are can this knife be re annealed, rehardened, & retempered & still expect to see the temper line? Have I ruined this piece of steel or can I salvage it?
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#2
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Any22...The answer is yes...you can anneal...re-harden...re-temper...and re-do everything, but the question is why? The presence of a temper line does not make a better blade, it is only an indication that the blade was differentially heat treated. A temper line is for aesthetic purposes only and adds nothing of quality to the knife what-so-ever, however, if that is what you're after, then you're probably going to have to re-do everything to achieve that effect.
If it were mine, and it was a good blade, I'd probably just go ahead and finish it as is... and either throw it into my drawer of "lessons learned" or make it another one for "me". In any event, the fact that there is no obvious temper line does nothing to suggest that the blade has been ruined. If the blade has survived the quench, and is not warped, and is indeed hardened as verified by a file, then I would not risk putting a known good blade through that strenous of a test again just to achieve something as frivolous as a temper line, especially after having spent so much time and effort after having beat a piece of 1" x 4" 52100 stock into submission with a hammer and anvil. That represents a lot of work to put at risk for a small reward. Last edited by Ed Tipton; 03-16-2012 at 07:42 AM. |
#3
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Mr. Tipton is right where I would be at here, in fact none of my blades, and a very large number of other excellent knifemakers, incorporate a differential heat treatment unless a csutomer specifically requests it for aesthetic purposes. What Mr. Tipton describes is on my mind right now since I just started using a new piece of equipment in my shop lab that measures steel tensile strengths. Strength is not the steels ability to easily deform (bend) but rather the exact opposite abilility to withstand deformation. In tensile testing, having soft parts in the sample leads to very low readings. The tensile test is merely a standardized and accurate method of measuring and representing the concepts, I also apply them succesfully everyday in my knives. Higher strength will allow a blade to take much more force in use without becoming bent or deformed. This is particularly useful at the very edge where strength = edge holding. What making the steel softer can do is increase toughness but this is mostly measured in sudden loading not bending, and would be the steels ability to resist fracture under a quick load. Many knife steels have a sweet spot for toughness that also allows for excellent strength via hardening and tempering as opposed to full soft. If the blade looks good and is nice and hard, I would say you have a keeper! But...
If the differential hardening is a customer request then what I would probably do is just do a lower teemperature normalizing or stress relieving and just redo the blade, heck it already hs been done a few times, why not one more? For really striking hamons (hardening lines) any of the 10XX series steels or W2 will harden only where you want them to and produce a very nice line for the customer. |
#4
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Thanks Gentlemen for the input. I only make a few knives a year strictly for the enjoyment of it. I NEVER take an order for a knife hence it becomes a JOB to me. I make knives I like & if you do too they are for sale you cant keep them all . As for the temper line Ive always felt a differentially temperedknife to be the best of the best so to speak and thats JUST MY opinion. The knife in question was finished when the question was asked It is certainly hardened and made a servicable knife, temper line does show up near the handle. the first hardening had a beautiful temper line, either the 2nd or third time I must have over heated the back and quenched too deep hardening the full width of the knife, Im sure that the knife will make a servicable piece for someone. THE REAL PROBLEM is I know it aint what I meant for it to be & in the future if I am again uncareful would I be able to fix it. Also I would hate to misrepresent my work even to a knife novice. Again thanks for the input
Last edited by Any 22; 03-19-2012 at 06:36 PM. |
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art, blade, edge, for sale, forged, hammer, handle, knife, knives, steel |
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