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- Jan 6, 2005
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- 9,680
Some time ago, I did a small tutorial on a method for straightening warped blades that involved clamping jigs and tempering cycles. I found that static clamping with little to almost no over-bend would take a set after a tempering cycle and the whole heart-pounding experience of a 3-point straightening jig could be avoided. Not a new technique, by any stretch(we did it all the time on a larger scale in the T&D industry) but the question was raised as to whether I was inducing stress or relieving it. I could not answer it at the time. I have read articles that suggested that the "damage" of warping is irreversible. They even go as far as to suggest that ALL mechanical and thermal events are forever recorded within the steel. Though, I have not seen any data to back that up.
It is my understanding that during the tempering cycle, as carbon atoms release and alpha martensite gets converted to beta martensite most of the stresses within the blade are relaxed... This is why the blade retains a "set". I have always felt the plastic deformation that results from straightening on a 3-point press is an unnecessary risk. When I clamp a warped blade to a straight piece of steel, there is only a slight preload on it... nowhere near enough to push the elastic limit. If simply running it through a tempering cycle "locks" it in place(even with an 80% success rate), why would anyone resort to a straightening press if they didn't absolutely need to? In the past I've had vice-straightened blades return to a warped state from a temper cycle or grinding operation.
So I ask...
Do you believe that steel has a memory of every mechanical and thermal event it's been subjected to?
Do you believe that any attempt to correct warp only succeeds at inducing more stress into an aready flawed blade?
Rick
It is my understanding that during the tempering cycle, as carbon atoms release and alpha martensite gets converted to beta martensite most of the stresses within the blade are relaxed... This is why the blade retains a "set". I have always felt the plastic deformation that results from straightening on a 3-point press is an unnecessary risk. When I clamp a warped blade to a straight piece of steel, there is only a slight preload on it... nowhere near enough to push the elastic limit. If simply running it through a tempering cycle "locks" it in place(even with an 80% success rate), why would anyone resort to a straightening press if they didn't absolutely need to? In the past I've had vice-straightened blades return to a warped state from a temper cycle or grinding operation.
So I ask...
Do you believe that steel has a memory of every mechanical and thermal event it's been subjected to?
Do you believe that any attempt to correct warp only succeeds at inducing more stress into an aready flawed blade?
Rick
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