starting over

Dustin

Active Member
so i've heat treated a large knife made from 440C. and i ended up with a RC of 45, Not so good. can i reverse the process and try again? i know were i went wrong i soaked it too long. this is the first time i've used my new oven and did it by myself.
 
Dustin, how long and how hot did you soak it? Ideally it should be about 1875F for 30 - 40 minutes, but even up to 2 hours shouldn't ;ead to failure as long as it's protected from decarb. If it wasn't protected, you may want to grind a few thou off before doing it over.

Rob!

Rob!
 
I soaked it for 1hr at 1950F. i did have it in a pouch.there was a little carb on the handle.
 
Just reharden. When you austinize the steel all the martensite from the previous quenching will be converted to austinite. If for some reason you believe that you have grown the carbides way big and have increased the brittleness of the steel you could do a subcritical annealing (spherodizing) but that would be the only reason that I could think of to do anything more that austinize and quench in air.

Doug
 
Dustin

RHC 45 is not a likely result from that HT. As a matter of fact, I'd predict more like RHC62 (though possibly some grain growth.) If you are getting a reading of 45, I think there might be something affecting the reading. Possibilities would include a burr - testing on a non-parallel surface - something on the blade or anvil as little as a human hair - or lots of other things. I have used 1950F (plus cryo) for customers who wanted 440C harder than normal (and were willing to sacrifice toughness). It came out of quench at 62 and out of cryo at 63.5.

1 hr at 1950 may not give the blade characteristics you want, but it did not lead to RHC45.

Hope that helps some.

Rob!
 
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