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Lar45

Heat treat fracture, or hammering too cold?

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Hello everybody

I'm making a knife for my buddy.  The blade is 52100 and G-10 black and orange scales.  My buddy is a vet, so the pins are supposed to look like dog paws.

wayne-01.jpg

Everything was going fine until I went to heat treat it.  I'm not sure if the steel got cooked or if I tried to take out a warp when the steel was too cold.  I used some very light taps to straiten out the mild warping.  If anyone could give me some advise, I'd appreciate it.  I have a propane fired forge.  I heat cycled it 3 times, then took it to just above orange and quenched.  While it was still hot I tried to straighten a couple of warps, then put back in the oil to finish cooling.  It went straight into the preheated toaster oven set at 400F for three one hour cycles.  After the last cycle I pulled it out and noticed the fracture after I wire brushed it off some.

wayne-02.jpg

I had a hard time getting the blade up to the right color in the forge and noticed afterwards that the bottle was going empty.  So I'm wondering if the problem might have been from having the blade in the forge for too long trying to get it up to the right temp.  I ground out the profile of a new blade and with a new propane tank I was able to heat treat it just fine.  I left the steel full thickness without grinding the angle on the blade.  Any help would be appreciated.

 

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you hit it with a hammer after hardening ? what did you expect

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I was hoping to be able to iron out a couple of small wrinkles.  I had read somewhere that you could quench in oil, take it out while still hot, straighten any warping, then back to the oil until it was completely cooled.  Then into the tempering oven...

I'm taking this to mean that it was bad advise? 

What would be the proper way to take out any warping of the blade after quenching?

TIA :)

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removing a warp by hand is not the same as using a hammer, the impact of which only added more stress to the un tempered steel, Even then the warp needs to be removed before it gets down to 400F or so, when the martensite sets up

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Thank you for the links and comments, that's exactly what I needed.

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to me that fracture pattern looks like you were forging it too hot. Normally cracks made by cold forging or post hardening are less tress like and more like closed hairlines in my experience

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I’m with Daveon this one, those cracks look to me like that blade was seriously overheated.

Do you still have the piece you cut off?

If so, put it in the vise, put on your face shield apron and jacket and break it, let’s see the grain structure.

Im betting it looks like cottage cheese.

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It looks like heat cracking to me,  my experience with after quench cracks tend to be almost clean snaps. But then I like simple steels. And I never adjust after a quench, when it comes out warped I re-heat and re-quench. Then I look at why it warped, too thin, heat uneven etc.

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