Will tempering cause finished A-2 to scale or discolor?

M

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Nov 22, 2015
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I have already heat treated and snap tempered a couple A-2 knives I was working on for a project. When I got them all cleaned up and checked their HRC they were a lot harder than I had hoped they would be (they are 61-64HRC). I would like to have them down in the 59-61 range. The problem is I am short on time and won't be able to re polish them up so I am wondering if I temper them at 350-400 will I see any discoloration and scaling? This is being done in normal atmosphere, though I can wrap them. Thanks for any advice anyone can offer.
 
It will not cause scale though it will cause them to turn a straw color or maybe even some other colors if there are contaminants on the blade.
But should clean up easily. Wrapping won't help.
 
At that temp you will have a discolouration in the straw/brown range, it's not scale so to speak and comes off easy. Even steel wool will take it off.
tempercolors2.jpg
 
Thank you guys very much. That answers the my question. But I have one follow up for you, the knives already have an edge put on them. The re-temper shouldn't cause any issues with cracking the edge like the hardening process could on a thin edge correct?
 
No won't hurt the edges,but I have a question. Why do have an edge on a knife that is not finished? Good way to get a serious cut. Edging the blade is the last step I do after everything else is finished including the sheath.
 
The blades were supposed to be finished for our purposes. They are being used for some materials testing. Long story short, we didn't realize how hard they were until after they were cleaned up on the belt sander and an edge put on.
 
Seems to me that you make might need higher temps for a2. If I recall, to hit those rockwell readings I had to go to 700ish
 
I ended up re tempering them and they ended up in the range of 59-60 HRC. I am pleased with that. I thought you guys might find these neat, so here are some of the pictures of the A-2, O-1, and D-2 knife edges I am doing the testing on. There is also a picture for each at 200x showing the 3D profile of the knife with a plot of its geometry at the edge. It is amazing how bad they look under 200x magnification. (their actual edge quality isn't very critical for what i'm doing).














image free hosting
 
The whole knife was touched to a 120 belt, then the edge was put on using a tru-hone with I believe a fine wheel (not certain on the actual wheel), then I went back over it with a Lansky from course to fine.
 
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