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Robert D.

Broken O1 blade

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I know its been a long while since I have posted anything, I have been very busy with non knife related things these past few months ( Prepping my older two children for their new " Gifted and Talented" school they start this summer, and welcoming a new baby boy into the family )  but have finally found some time to get back into the shop and work on some projects I had laying around just needing some finishing work done to them. 

On this one ( and the two as of yet unbroken ones I still have floating around ) I did something a bit different on the heat treat, I did the standard 3 normalization cycles, but then when I went to do the hardening phase, I built the fire up ( Charcoal forge ) and placed the blade in my baffle pipe ( thanks again Alan for that tip ) and let it come up to the point of seeing the shadows, then I kill the airflow and watch the blade closely for color changes, basically a poor mans soak for about 10 minutes from the residual heat of the burning charcoal already going around the pipe.  Afterwards a 2x round of tempering at 450f in my oven on a firebrick with an oven thermometer watching the temps. 

To me, the grain looks a bit bigger then it should be, So my thoughts are either my soak process got hotter then I thought it did, but I didnt notice any major color change during the no airflow process ( done in the dark at night outside ) or my normalization process wasnt done well enough prior to the hardening cycle. But I am open to suggestions, I am going to forge out a few more blades out of this O1 I have ( half inch rod stock ) and try to bring the blade up just before the phase change and then kill the airflow and see if the residual heat causes it to hit the phase change temps without airflow. 

So, thoughts, suggestions, critique on my thought process on getting more out of O1 with a simple solid fuel forge, I have about another 6 feet of this drill rod left over, and wont be in a position to buy a heat treat oven for at least another year, and I really like forging O1 out for smaller blades. But everything I have made from it prior was done without a soak of any kind so I know I am not getting the most of out this steel. 

 

20180516_075641.jpg

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Hmmm...  Yeah, that's a little on the big side, but not too bad.    I suspect too much heat while forging or too hot on the normalizing cycles, but without looking over your shoulder while you're doing it I don't know what else to tell you.  I do know I've made matting punches out of O-1 drill rod by deliberately growing the grain, and it took more time at heat than I was expecting to grow seriously huge grain in the stuff.  In fact that grain you're showing was as big as I was able to get it until I did a minute or two at just short of sparking hot. 

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I hadnt thought of forging temps being part of the cause, I forged this blade and the 2 others a good while back, so I cant honestly recall. I guess I ruled that one out thinking the Normalization would have solved it if that were the case, Guess I should do a bit of break testing to see if my normalization process isnt doing enough work on the grain structure of the steel. 

Yay experiment time..... 

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