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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 03-16-2007, 03:24 PM
caseynz caseynz is offline
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01 too hard.

hi people,hopefully you can help me out.
ive just made a knife out of 01 bar stock and ive hardened it by heating to a little past non magnetic then edge quenching in oil.while still pretty hot i put it in the oven at around 400 f for just over an hour.a file still scated over the edge after this , so i raised the temp a bit more for another hour and still its too hard.
im using a kitchen oven with no proper thermometer but on the first cycle the blade came out bronze and the second time it came out purple,so i think the temps are pretty good. any ideas how to soften it up a little more or is this ok.its going to be a fillet knife so it will be very thin and i dont want it snapping too easily. any help much appreciated.
cheers case
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  #2  
Old 03-16-2007, 05:29 PM
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Ed Caffrey Ed Caffrey is offline
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First thing you MUST do, is get an oven thermometer so you can KNOW exactly what the oven time is. For O-1, around 425-450F should produce a good working hardness. The next thing is the tempering time.....go for at least 2 hours. Two things that cannot be separated when it comes to steel is time and temp. It takes a specific amount of time, at a given temp to create a specific matrix transformation.

Concerning the oxide colors..... did you clean/sand the oxide off between the temper cycles? If not, the drastic color change you saw was due to the fact that oxide color is cumulative...meaning that a new layer of oxide forms over the old one. This makes the light reflect/refract differently, and produces a different color. The changes in a steel's matrix take place every 25F. So if you ever have this situation again, temper the blade again, and 25F higher than the previous tempering cycle, and so on until you achieve the hardness level you desire.

I personally think that the "brass rod" test is pretty the simplest and most effective way of determining the proper working hardness for a blade.


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Old 03-16-2007, 06:38 PM
caseynz caseynz is offline
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thankyou for the reply.is it too late to retemper now or do i have to start again by annealing and normalising?. i will get a proper thermometer .
yes i did sand the blade between tempers.thanks for your time.

Last edited by caseynz; 03-16-2007 at 06:55 PM. Reason: need to add more
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Old 03-16-2007, 09:14 PM
Larrin Larrin is offline
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I'm not sure why the file biting the steel would mean that it's now a good hardness.
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Old 03-16-2007, 09:43 PM
caseynz caseynz is offline
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i will grind it out and see what happens.up till now ive been using scrap steel to make my knives and if they where this hard then the edje was to brittle. maybe the 01 can handle it.
cheers casey.
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Old 03-16-2007, 11:21 PM
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As long as the steel is still harder than you'd like, you have the option of re-tempering it. Just raise the tempering temp 25F, then run the brass rod test. Optimal working hardness is achieved when the edge slightly flexes over the rod and returns to true. If the edge lightly chips, go up another 25F and re-temper. The edge is too soft when you flex it over the brass rod, and it remains flexed....thats when you got problems.... if that occurs you have to go back through the whole heat treating process (anneal, harden, temper, etc)


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Old 03-17-2007, 03:22 AM
caseynz caseynz is offline
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thanks ed and larrin.ill try the brass rod trick and let you know.
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Old 03-20-2007, 05:19 AM
caseynz caseynz is offline
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the knife turned out pretty good after all. the o1 steel is so much better than using scrap steel and guessing everything along the way.ive just got to get a few more things sorted out to get rid of some of the variables and ill be happy. ,once again thanks for your advice.
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