Interesting cracks today with O1 - any thoughts?

cpirtle

cpirtle

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Was heat treating a blade made from 1/4" PG O1 today by my normal method - 3 normalizing/annealing runs, 1550 degree w/soak, quenched in McMaster fast at 130 degrees.

This particular piece of steel is from a unkown source and I've had it sitting in the shop for several years. It was purchased loose in a 1"x8" piece so I don't have any more of it. It was roll printed with manufacturing information, it was only partial but clearly marked as O1.

On this particular blade, the hardness after quench & before tempering was in the mid 40's and I noticed what looked like delamination (I know it's not laminated, just using the term to help describe the cracks) or stress cracks running through the spine, top and bottom of the tang and into the blade edge. No cracking or abnormalities on the flats or blade bevel.

Pretty sure this is not an equipment or process error as I heat treated 4 other blades today with perfect results, just this one failed.

Any thoughts or suggestions? I can post pictures tomorrow if my description isn't clear enough.
 
Please post photos.I would have guessed maybe decarb but it is PG .
 
Sounds like something occurred during the manufacturing of the steel. I had two A2 blades split like a banana peel during HT (cryo) that looked exactly like a delamination. I got the piece of A2 from a former forum member that got the steel from a discount store. Go figure.
 
#1- There is no need or benefit in normalizing PG 01 unless you forged it. #2- 1550° is maybe 65°/75° higher than it needs to be. #3- 01 does not like fast oil.
 
Yeah....1550 is very high for O-1. 1475 for 20 mins. does the trick.
 
I did that to an O1 blade by overheating it and quenching it in the wrong stuff (goop). Looked like it was shattered internally and just showed on the thin edges.

So far I've had good luck with 130deg Canola instead.

-Daizee
 
Like already mentioned, the temp is too high. I soak mine in my Evenheat at 1500 max. Then, it's quenched into the slower Park's AAA oil.
 
Danbo said:
Like already mentioned, the temp is too high. I soak mine in my Evenheat at 1500 max. Then, it's quenched into the slower Park's AAA oil.
Click to expand...
Hi Danbo. Love your avatar. Just for the hellavit, try lowering to around 1475/1485°. I do a 20 minute soak at 1485°, and get excellent results. I also use Parks AAA, and an Evenheat. I lowered my temp after reading a lengthy post by Kevin Cash, and got no less than equal results, and seemingly a little less warpage, but I understand that if something is working right, there is a relunctance to change. Just suggesting a try. If you are getting exactly what you want, disregard.
 
Thanks for the pointers - I'll use slower oil next time and drop the heat a touch. I don't have much O1 and a lot of other stock on hand so I won't be working in it much. Not sure it was the cause but my Sugar Creek took a dump on me right after this, so I have a new Evenheat on the way and will use the SK for tempering.

The only thing I'm still stumped on is even if the heat was high and the oil was too fast, the blade should have hardened. This one never did, double checked with my penetration hardness tester.
 
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