re-quenching 1080 steel

samuraistuart · Mar 20, 2013

I've searched a bit, but can't quite find the answer I'm looking for. Say a person is making a knife out of 1080. Stock removal. Let's say EVERYTHING has been done correctly thus far (edge thickness, etc), but the knifemaker just isn't QUITE sure if the temp of the blade at the time of quench was high enough. Not TOO hot...not hot enough. There has been no normalization done, just a hardening quench. If the knifemaker was trepidatious about the temp during first try, and wanted to RE-DO the hardening process, heat to critical and quench and temper AGAIN, can he do so without any normalizing/annealing procedures? I don't mean CAN he do it, I mean...would you recommend this, and would it be OK on the steel and grain size, to just go ahead and bring it back up to 1475 or so and re-quench? Thanks for the replies.

mete · Mar 20, 2013

Not a problem. Normalize or do a subcritical anneal [1200 F for about an hour and air cool , then reharden.

gredpe3 · Mar 20, 2013

Really, an hour? 1st time Ive heard that for 10xx series .

gine · Mar 20, 2013

Make sure you test the blade with a good file. If it skates across then the blade was hardened. This works for me with a simple setup.

sintro · Mar 20, 2013

gredpe3 said:
Really, an hour? 1st time Ive heard that for 10xx series .

Mete was talking 1200f for an hour to anneal the steal. For normalizing what people generally go for this sort of steel is this kind of routine.

Here is a basic HT regimen forn 1084:
1084 HT:
refine grain and normalize -
heat to 1500F and air cool to black, then quench to cool
heat to 1350F ( just non-magnetic) and air cool to black, then quench to cool
heat to 1200F ( still magnetic) and air cool to black, quench to cool
Straighten any warp or twist

-Quoted from Stacy in this thread

Bo T · Mar 20, 2013

If I understand the process, you think that the blade was heated below the critical temperature before quenching. If this is the case then you shouldn't need to worry about grain growth. During the quench there were some stresses placed on the blade but unless you have some micro cracks austenizing above the critical temperature should relax those stresses. I don't know about the possibility of micro cracks or what can be done about them. So reheating and quenching again should have little or no effect on grain size and, hopefully, the blade will turn out the same as if you had done the quench right the first time.

sintro · Mar 20, 2013

I've normalized, quenched, tempered to totally soft against on accident(basically annealed), normalized again and quenched and tempered with a piece of 1084 and it worked out fine.

Don Hanson III · Mar 21, 2013

I don't normalize or anneal when I 're-heat-quench' a blade. This with W2, W1 and 10XX steels.

samuraistuart · Mar 21, 2013

Well, I think you guys have totally answered my question. Thanks a million. I really appreciate it.

mete · Mar 21, 2013

When you do stuff at 1200F you avoid decarb, scale ,you of course temper the martensite and create many points for austenite formation.Straighten if necessary then reharden !

samuraistuart · Mar 21, 2013

Bo T said:
If I understand the process, you think that the blade was heated below the critical temperature before quenching. If this is the case then you shouldn't need to worry about grain growth. During the quench there were some stresses placed on the blade but unless you have some micro cracks austenizing above the critical temperature should relax those stresses. I don't know about the possibility of micro cracks or what can be done about them. So reheating and quenching again should have little or no effect on grain size and, hopefully, the blade will turn out the same as if you had done the quench right the first time.

Bo T, you're exactly right, I wondered if the blade was heated below critical before quenching. And yes, this is exactly what I was worried about....the stresses caused during the quench. Even after a temper to bring down the RC and lower stress, I wondered if it was necessary to go ahead and anneal/normalize before retrying. Looks like the answer is "no", but definitely wouldn't hurt. I'm trying to learn the color of the steel at critical, doing all my heat treating in the dark. I'm always always always worried about overheating the blade too much, being too cautious maybe. I bet if I played with burner position, and adjust the flame with the control knob, I can figure out a way to get to 1475 and hold it there. Thanks for your help!