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Brenno

Time to break some stuff.

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Hey my friends.

Thanks to all for the advice in previous threads on how to approach my heat treating with my newly built kiln. I thought you might enjoy my test results. Feel free to offer further suggestions too.

 

I skirted the suggested triple quench for this round, but this is what I did do, and I got some progress:

 

I had three flat bar offcut samples. 6mm (1/4") thick. 20mm (3/4") wide. And about 200mm (8") long.

 

I was unsure if I would be able to snap them so I also included a knife which I forged a few months ago, but didn't like. It was only 2.5mm thick at the blade.

 

Procedure:

First I normalised all pieces thrice at 820C.

 

I then took piece number 1: Soaked it for 10 minutes at 800C (1472F).

Austentite starts at 790C (1450F) for 9260 I've been told.

 

Then quenched in 3 lites of vegie oil.

 

I then took piece number 2:

Soaked for 20 minutes at 820C (1508F)

Quenched in a different 3 litres of vegie oil.

 

I then took piece number 3 and the knife blade.

Soaked for 10 minutes at 870C (1600F). 870C being the suggested quench temp from the previous thread.

Quenched again in 3 litres of vegie oil.

 

Then they were all tempered together at 350C (660F) for 1 hour.

 

Today I tried to snap them. Huh!. I bent them, to varying degrees. This photo shows my success. Believe me the effort put in was far increased as they got tougher from 1 -> 3.

Tests_0008.jpg

I used a 14" Pipe to bend them. Trust me it was all I could do to put that bend in #3, given my rather rickety work bench anyway.

 

I then snapped the knife. My wifes grand dad who was originally a blacksmith and later a gunsmith inspected the grain and he was very happy with it. It's smooth and microfine.

 

Here's a fun movie I made to show my breaking games.

Edited by Brenno

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660 degree F is too high for tempering a knife blade. I get real good results at 400 degrees F., that's about 205 degrees C. If you still have part of that blade you might want to check it for edge retention. Push the edge of the blade down onto something like a nail or the edge of a steel table. I think what you will see is that the edge bends and stays bent. What you want to happen is to see the edge bend and then return to shape when pressure is let up without any cracking in the edge.

 

Doug Lester

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Brenno,

 

What conclusions have you reached from your experiment?

 

~Bruce~

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Thanks Doug. I have been recommended 450F before, which I've read should give around 58Rc. But I'm not making knives. I make swords usually, and I'd rather have them bend than snap, for safety reasons, in case any mistakes are to be made in handling. So at 660F I'm aiming for 52-53Rc hopefully - even 50 would be fine.

 

I may still conduct some tempering experiments on some mock up blades, to see where they snap.

 

Hi Bruce - Well I know 870C works, without noticable grain growth or loss of durability. I might do somem further tests at temperatures between 820 and 870, and also vary soak times.

I'll use skinnier pieces next time so I can hope to break them. :)

Edited by Brenno

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Hi Bruce - Well I know 870C works, without noticable grain growth or loss of durability. I might do somem further tests at temperatures between 820 and 870, and also vary soak times.

I'll use skinnier pieces next time so I can hope to break them.

Looks like 870C was the right temperature. You could probably drop the temp. a little but, looks like you would have to drasticaly increase the soak time. Must be the affect of the Si. Next round of tests do up two pieces just like #3 but, run one of them through 3 hardening cycles. Temper together. Then break them and compare. You will probably need a sturdier bench!

 

~Bruce~

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You will probably need a sturdier bench!

~Bruce~

I have read that technique mentioned a couple of times here. I will try it for my self, and video the destruction for toughness comparison. I can't get good grain pics but will let you know what I find.

Next time I will make mock blades shapes for the test, and temper it at 250C instead. I've been recommended that if I cant snap them I can notch them with a dremel wheel.

Cheers

:)

PS gosh I love my new kiln :) :) :)

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Glad to hear your experiments went well, despite some of my advice in the other thread :D . Turns out, I was re-reading Verhoeven the other night, when Lo, and Behold!, page 86 has a big, bold note: The ASM diagrams use As for A1, and Af for A3 (~ AC1 & AC3). So, I was wrong when I said As = Aust Start and so forth. You want to Austenitize above ~A3, but I think you figured it out...Congratulations. I want to see some broken steel!

 

Thanks,

Brian K.

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