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Chris Paul

Why did these chisels crack?

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Any help on how I can avoid this failure in my next attempt at forging chisels will be greatly appreciated. 

The material I'm using is new 5160 1" round bar.   Using a gas forge with temp control, hammer and press for forging.   After forging I did 2 normalizing / thermal cycles, first one at 1600, then one at 1550, soaked for 10 min each.   I let them cool to the touch before the next cycle.  Quench was done in 120 deg canola oil.   

Both chisels show longitudinal cracks. 

What did I do wrong? 

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It's possible there were a few small localized spots where the steel got cooler than I would have preferred while in the press.  The dies were not preheated.  I'd say low orange / high red heat on the last squeeze.  Really only used the press to straighten.   

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Not the last squeeze *any* squeeze!  Since both had cracks but they don't look the same I would guess process over material.  (Though I am sure you have since checked to be sure the steel was what it was sold as and not an air cooling steel)

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I have good luck working spring in the high orange to low yellow and go back to the fire when it cools into the mid high orange.

Frosty The Lucky.

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