Edge cracks in O-1

Hey guys!

I've been messing around with O-1 recently, and am having a difficult time avoiding one small crack on the edge of the blade. (Usually one, I think I got two cracks one time.) It starts off at about 90 degrees to the edge, and then wanders a little. They're usually at least a quarter of an inch long, sometimes up to 2/3 thirds the width of the blade and go straight through the blade, appearing on both sides. They almost always appear halfway up the blade, or occasionally out towards the tip. I've yet to figure out what I'm doing wrong, or even when they are appearing. I typically won't know anything about it until I start to clean off the scale and do a little grinding on it after forging. I normalize all my blades. Am I just getting it too hot, or striking it when it's not hot enough? I've not been having this problem with 1095 and 1084.

The O-1 I'm using are solid round rods, 1/2", 3/4" and 1" in diameter. I get the cracks whether I'm doing a wide heavy blade from the 1" rod, or a smaller blade from the 1/2". It's got me sorta confused, as I've not been able to come up with any answers on my own. Any and all help will be greatly appreciated.

[Ed Caffrey]

Cracks in blades come from stress. We induce stress in just about every operation we do. Forging itself, Striking the steel when it's too cold, quenching in a media which is too "fast" for the steel, and many other things.
If the cracks are occurring/noticed right after forging, then it's likely that your striking the steel too cold. Once you hear a "tinny" sound when striking, STOP HITTING IT! Your already past the lower forging range for that material.

[mete]

O-1 likes to be preheated at 1200F before bringing up to forging temp. Do not forge below 1500F.Cool in ashes when normalizing or annealing.

[B.Finnigan]

I was just working on an celtic arrowhead this AM and I am using 01 and I got a small crack twards the tip where it cools the quickest. I am used to doing quite a bit of black heat hammering on 5160 but I to found out the hard way with 01.

I guess I'll have to try harder not too forge after it's cooled off too much I've been aircooling it after normalizing, would that help to cause cracks to appear? I'll cool the next one in a pile of ashes or something similar like mete said.

[mete]

O-1 has high hardenability ,sometimes acting as an air hardening steel in thin sections. So normalizing can actually harden it. So the slow cooling of annealing is needed.

Well, maybe it helped! I forged two blades this morning, both of which are void of cracks. Thanks for the tips.

[cricket]

I had the same problem with 52100,turned out I was working the steel too long. You have to make yourself stop as soon as you hear the sound of the hammer start to ring.

[B.Finnigan]

I am noticing that the 01 drill rod is cracking even when I stop hammering before it gets dark. The last two arrow heads I have forged all had cracks show up after I started finish filing them. Every five heat/hammer cycles I have let it normalize to room temp and it still cracks when the thickness tapers down to 1/16". I will not be attempting any blades with 01 since the dark heat is when I can really see the detail and what needs further work.

Do not air cool them. *see above* I think that cooling my blades slowly made the most difference. I've forged a couple more in the past few days, with no cracking. I wasn't even terribly careful with this last one...