First Knife total Failure for me.

Knife making is easy, as long as you have someone to show you how!
We have never had a blade warp after we started use 3, 35 second post forging quenches from critical temp. in our quenching oil, Texaco type A, then go to the normalize cycles.
 
A failure? Naw, that was a stepping stone. I'm not familiar with truck springs, but most steels are recommended to be double tempered and at least you know it hardened.
 
I have recently made a small skinning knife(with the same steel as the bowie), along with it I hardened and tempered a piece of the same steel, just to test with. This time i did two temper cycles both at 450 for 2 hours each. I put the testing piece of steel in a vise and pushed on it hard and it broke, it hardly bent at all before it broke.(like maybe 5 degrees).
I also ran my file over it and it is for sure harder then my old fillet knives, seems close to my mora of sweden knives which i think is 58 Rc but it hard to tell for sure.
I assume this means its still to hard and needs to be tempered higher?
 
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I have a few questions:

same truck spring steel?

This sounds nitpicky, but do you have an oven thermometer and was the oven stable at temperature first?

how did you bend? I can snap a lot of blades instantly by trying for a really sharp bend

and the last one, because this is my suspicion - did you burn the steel? What I mean is, how did you do the heat treating?

(I also do differential tempering using a torch on the spine of the blade, but that is highly dependent on steel- you can make matters worse on 5160 doing that if it cools wrong)
 
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First rule: Never push on a blade to break it, you can end up hurting yourself, always pull and you fall free. Always wear safety glasses and plan that if it breaks you will not fall into something that can hurt you.

You never know what that truck spring is made of, some springs are of good steel, others are full of faults. You chase an invisable foe when you do not know the quality of the steel you are using.

I wish you lived close to the Willow Bow, your enthusiasm impresses me, would love to teach you how to forge, harden and temper a great blade.

In the mean time, keep on with your experimenting.

A few questions: What is your quenching medium?
How hot do you work your steel?

And a comment: The 450 temper should have been plenty. If you want to continue to work with that steel, be sure it is free of surface faults ie. scratches or dents.


Rex just did some hardening experiments in his Lab. with multiple quench:
Watching the steel cycle down through the phaze change,
1 st quench time 15 seconds
2 nd quench, time 10 seconds
3rd quench, time 2 seconds.
tempering temperatures, increasing 15 degrees for each cycle through the three samples Resulted in an increase of 20,000 psi strength.
 
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