Cruforge v blade failure

rodriguez7

rodriguez7

Gila wilderness knife works
Joined
Feb 1, 2009
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so I recently heat treated 2 blades out of cruforge this week, getting ready for an elk hunt. These were heated past magnetic, held for 5 minutes to equalize, then quenched in parks 50. After it cooled to room temperature, Then into dry ice and acetone for an hour. I tempered twice at 400 degrees. Well today I chopped into a piece of oak, this blade has a quarter inch spine. After 2 chops the blade snapped in half. It seems extremely brittle, like glass. Was the tempering temperature to low? I have another one in my shop I was going to finish tonight. Should I temper it at 450?
 
Parks 50 is too fast. Dry ice created way too much stress additionally.
 
Canola or parks aaa are good choices. Quenching too fast increases stress.
 
So is it possible to re heat treat the blade I have almost finished? Or is to late?
 
It's stock removal. I just fired up my forge, gonna give it a shot
 
What did the grain structure look like in the one that snapped? Usually using to fast of a quench will stress the blade to the point it cracks befor you get to the temper. But generally speaking once you temper (especial at 400°) you should have dropped that stress down to where it should be. I don't personally see the quench being the problem unless A you over heated it or B it had a small crack befor tempering. Over heating will enlarge the grain size and weaken the steel. And a small crack is a stress point that easily propagates under load.
 
I gotta echo JT on this for the most part. If quench stress is going to be a factor, either the blade will visibly crack before temper, or a fine crack may occur that is to small to even see when finishing, particularly if a belt finish is used. Then a hard blow like a chop will cause it to fail. Typically if CruV is quenched too fast and survives, (done that) what suffers is edge stability in chopping bone or antler, which shows as chipping. For a 1/4" thick blade to snap clean from chopping wood- well, sounds like a hairline crack from the quench that wasn't caught.
 
The grain structure looked extremely fine. To me it seems like it was just to hard, like the temper wasn't high enough. I re heat treated that other blade, tempered at 400 for 2 hours. The tip snapped off just doing some light prying in juniper. I'm thinking of tempering it at 475, and testing again, this is 2 different blades, with the same type of failure. It just seems really brittle to me. But the grain structure was very fine looking.
 
Seen that! That's what im guessing my trouble is. To high of an rc, with the toughness of glass!!!
 
So what if I try, getting it up past magnetic, hold if for 3 minutes, and quench for 3 seconds in warm canola, then put it between some aluminum plates, and let it air cool!
 
I'll send you the broken piece next week after my elk hunt, thanks.
 
So, since i haven’t had a chance to send a piece out to JT. I re tempered a broken blade i had laying around. I tempered it in the kitchen oven, at 450 degrees this time. And so far it has held up really well chopping wood, and some decently tough batonning. I finally got a temp probe and gauge, and found my toaster oven varies from 25 degrees, to 50 degrees off. So I’m guessing that was my problem. Just to hard out of quench, using parks 50. I may order some triple A when i get some extra cash. What kind of edge retention should i expect out of this steel, at around 58 to 60 rc, for a hunting/skinning blade?
 
We have had good luck with McMaster carr fast quench(which is a little slower than parks) for cru forge V.. Though in all honesty we have never had a cracked blade using parks either. Personally Id leave it close to 60rc for a hunter.
 
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