ats34 warp issue

johnnym

johnnym

Joined
Dec 13, 2005
Messages
170
I am having issues with blades warping but here is the kick. I am oil quenching ats34 blades and when i take them from the oil they are fine, no warping. I then put them into the liquid nitrogen for about 2 hours. When they come out, some of the blade are warped. It seems that they warp right on the plunge line. I am able to get them straight after the first temper, but it is frustrating. Has anyone else had this problem?
 
I wonder how you've put the blade into the LN.There was a similar problem someone had who laid it down instead of suspending it. ATS-34 like other stainless steels lends iteself to plate quenching .Do a search on that, there are lots of posts. Much more convenient than oil.
 
My guess is that you are creating stress when you oil quench the blades.That plus the possibility that there is a high amount of retained austenite, distributed unevenly in the blade. The LN allows the stress to warp the blade as the retained austenite converts to larger martensitic structure.
Stacy
 
Mete,

I am putting the blades in the tubes that came with the dawar, i put the blades in the tube and then put the tubes in the LN. I was using a oil quench recipe that i found on a knife makers website. I have plates that i use for D2 and i will try using them instead of oil to see if that fixes the problem.

Thanks for the advice.
-John
 
Yes it is. Makes ya wonder why someone would want to use oil to harden it :D Then again, i dunno anything about ATS 34
 
Logem and Pohan:

ATS34 is the same basic chemistry as Crucible 154CM. Here is a link to the HT pdf at Crucible.154CM HT datasheet

You'll see that it is considered primarily an oil quench steel, for that is how their data are written. They also say you can use a 4bar (60PSI) gas quench, which is what someone like Bos uses.

Leaving it in still air will result in significant retained austenite and low hardness. Plate quenching cools much faster than still air, so it is plenty adequate, and, as mete said, much more convenient than oil.

johnnym, I would recommend that you first put the blade in your freezer and let it get down to that temp. Then, suspend it above the LN2 for awhile and let it cool more before slowly lowering it into the liquid. Also, inspect your grinds to make sure they are very symmetrical side to side before heat treat.

If the problem continues and you are making smaller blades, consider trying it once where you simply profile and drill holes, then heat treat (plate quench) completely and grind them afterwards.
 
So the correct sequence is quench, cryo then temper? Would quench,temper,cryo then retemper relieve those stresses that are warping the blade? I know nothing about cryo so don't take that as advice,just trying to learn something.
 
mete said:
I wonder how you've put the blade into the LN.There was a similar problem someone had who laid it down instead of suspending it. ATS-34 like other stainless steels lends iteself to plate quenching .Do a search on that, there are lots of posts. Much more convenient than oil.
Click to expand...

Break out the plates and be done with it :)
 
This is great information guys, thank you. I read several HT specs for ats34 and went with the oil quench, mostly because i did not know any better.

Fitzo, I will try your cryo technique, i have just been placing the blades right in the liquid and letting them "boil" before putting the top back on the dawar.

The symmetry of my grinds is suspect since i am not very experienced, however i have been leaving quite a bit of metal on the blades and then finishing them after HT.

I will post my results once i try these new methods.

Thanks again,
-John
 
Martin S. said:
So the correct sequence is quench, cryo then temper? Would quench,temper,cryo then retemper relieve those stresses that are warping the blade? I know nothing about cryo so don't take that as advice,just trying to learn something.
Click to expand...

I cryo after quench, Martin. There are those who do a "snap" temper (lowered temp, perhaps 200F) or one full temper before cryo. The steel manufacturers don't even seem to be consistent about which they recommend, so it may be worth trying if his warping problems persist.
 
Martin, you have a choice.You may quench, cryo, temper .If you are the cautious type you can quench, "snap temper" [300 F] ,cryo, temper. The final temper for complex steels such as ATS-34 should be a double temper.....Cryo can be done either by putting the blade directly into the LN or suspending it above the liquid.
 
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