liquid nitrogen and 5160

[danpiotte]

I have access to liquid nitrogen at work now and was wondering if a dunk would do my 5160 blade any good. I also have a CRKT m-21 0-4 with a aus 6 (I think)blade. The folder has an anodized aluminum handle. Is there any harm risked if the handle gets dunked?

 

Thanks

 

Daniel

[Greg Thomas Obach]

5160 + liquid = a nice cold blade

 

Aus 6 + liquid= a chance that it will trip off some RA and turn it to untempered martesite

---- then it should be place in oven and retempered to reduce the chance of brittleness

 

 

theres alot of hype with undercooling steel..

[Doug Lester]

Maybe I should let one of the real metallurgists answere this but 5160 is not a real complex steel and I don't know if the real M_f point is below room temperature. None of the info I have from ASMI gives that data. Most ITT diagram only list the M₉₀point. It won't hurt anything if you do it but you might only be making the steel cold. It could help if you measured the HRC before and after the cryoquench to get an answere. Some heat treaters go from the normal quenchant to the cryoquench and then to tempering oven. I know from data on cryquenching a stainless steel that you cause less stress by going from the quenchant to the tempering oven, to the cryoquench, then back to the tempering oven.

 

Doug

[kb0fhp]

Maybe I should let one of the real metallurgists answere this but 5160 is not a real complex steel and I don't know if the real M_f point is below room temperature. None of the info I have from ASMI gives that data. Most ITT diagram only list the M₉₀point. It won't hurt anything if you do it but you might only be making the steel cold. It could help if you measured the HRC before and after the cryoquench to get an answere. Some heat treaters go from the normal quenchant to the cryoquench and then to tempering oven. I know from data on cryquenching a stainless steel that you cause less stress by going from the quenchant to the tempering oven, to the cryoquench, then back to the tempering oven.

 

Doug

 

 

Download Timken Practical Guide for Metallurgists - lots of good data there and free. There is a new edition out there - just go to the Timken site and download it.

Timken Practical Data for Metallurgist.pdf

[Robert George]

My understanding matches Doug -- that cryo converts retained austenite on high alloy steels (stainless, D2, 1V, 3V,...). The low alloy tool steels like 5160 won't have a bunch of retained austenite if heat treated correctly.

 

More importantly, the heat treat sheets from Carpenter, Crucible et al indicate that cryo has to be done on high alloy tool steels almost immediately after quench to be effective.

[kb0fhp]

My understanding matches Doug -- that cryo converts retained austenite on high alloy steels (stainless, D2, 1V, 3V,...). The low alloy tool steels like 5160 won't have a bunch of retained austenite if heat treated correctly.

 

More importantly, the heat treat sheets from Carpenter, Crucible et al indicate that cryo has to be done on high alloy tool steels almost immediately after quench to be effective.

 

 

What will happen when you quench steel in liquid nitrogen is that the LN2 will immediately turn to vapor and you will get a very persistent vapor phase - it is a very slow quench. Only vigerous agitation will break up the vapor phase. Another thing to concern yourself with is that all the LN2 will also turn to gas and create a suffocation hazard. This was well documented about 30 years ago when several people died when a manufacturer tried it.