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This all started when I was doing a forge temper on a blade, and it got a little too hot. It was nothing special, so I figured I would experiment. Instead of starting over, I water quenched. I repeated the same thing two more times, heating it to regular tempering heat this time. The result was a freaking tough blade. I haven't done much real experimentation with the process, but I tried the same thing a couple more times with different steels(I don't know any of the exact steels I used/recycled steel), and I've ended up with very tough and hard blades every time. Has anybody ever tried this?

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As a matter of fact, yes. This technique is really big in both the tribal and high-performance crowd. The idea is that the phase transformation from martensite to pearlite only happens on the way down, so if you heat the blade up and quench before it drops below critical, you can try and transform more austenite to martensite instead of pearlite. Many believe it also shrinks the grain, which would explain the toughness. A good temper is a must afterwards, though, since more stress is introduced through the multiple quenches.

 

Are you testing these blades specifically or just noticing a trend?

 

-Ethan

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As a matter of fact, yes. This technique is really big in both the tribal and high-performance crowd. The idea is that the phase transformation from martensite to pearlite only happens on the way down, so if you heat the blade up and quench before it drops below critical, you can try and transform more austenite to martensite instead of pearlite. Many believe it also shrinks the grain, which would explain the toughness. A good temper is a must afterwards, though, since more stress is introduced through the multiple quenches.

 

Are you testing these blades specifically or just noticing a trend?

 

-Ethan

 

i don't think he's talking about quenching from critical, but from tempering temp - he over heated on the first temper and quenched it.

 

there's nothing wrong with quenching from tempering temp that i can see - i always do it when i temper in a forge. i also think that a lot of us tend to temper on the hard side (many old knives would be in the very low 50's rc, for ease of sharpening and toughness) because with modern steels and techniques you can make a very hard blade that's still tough, so your over heating may not in fact be such, it really depends on the steel, but to rub out the effects of hardening completely you generally have to go to a silver/grey temper. and as with everything in steel, it's time and temperature, so if you do overshoot, quenching can minimise the problem.

 

the main problem to my mind is that if you over temper a blade with a hamon, you'll start to wash out the crisp definition of the different structures, and this starts to happen at just over 400f with most steels, so tempering in a forge can be problematic, particularly if the blade doesn't heat too evenly.

 

that said, you lose less hardness for toughness with a long soak at lower temps, than with quickly bringing it up to a higher temp.

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