What's he doing?

V

VaughnT

Well-Known Member
No disrespect intended to Andrew as he's one of the finest craftsman I've ever seen. But, I don't get what he's saying here.

If you watch the video, at 8:54 he quenches the blade three times and talks about, I'm guessing, making the grain pop or pulse.

I just don't understand what he's doing or trying to get across to the viewer. Any ideas? Is it an old wive's tale? Redundant if you normalize the blade? Only needed/beneficial on pattern-welded stock?

It doesn't look like it would add any real time to the process, and if it's beneficial to a forged blade....

http://www.dailymotion.com/video/x6cwk2_video-andrew-jordan-partie-1_creation
 
The feed was a little slow on my 'puter so I couldn't get to the section you were talking about (bummer) but the reason that most people who do it quench three times is to refine the grain. When the steel crystals reform as they shift from one phase to another, ferite to austinite or visa versa, the new crystals form on the border of the old crystals and are smaller. If you don't overheat the steel to austinize it this will refine the grain size.

Doug Lester
 
This triple-quench was prior to the hardening stage, he says. If he's normalizing before hardening, it's a technique I've never heard of before.
 
You could triple quench before hardening if you return the steel to the forge and austinize the blade again after the last quench, but I don't know why anyone would do it that way. I would rather do a triple normalization at that point. I might be wrong but I would think that normalization would reduce any stress in the blade better but the triple quench would still refine the grain if done right.

Doug Lester
 
It's called thermal cycling, and that's what he calls it in the video. I think he's a little on the quick side, but consistent with the way he understands it, I would guess. The steel is austenitized then cooled to below the austenitizing temperature. It does not require rapid quenching and can be done with a simple air blast, or a slow cool in still air. The point is to refine the grain of the steel as Doug has already noted. I cool it down to at least black but not necessarily to achieve room temperature (or below martensite start).

Normalizing in three cycles, quenching in three cycles, the job of grain refinement gets done all the same. The first way takes longer, the second shorter, but it does not require three days.

If you took a little longer in between heats you could straighten any warpage that occurred and set the steel up to be much less likely to warp during the final heat to harden cycle.

The magic in Three cycles is that realistically, given the usual tooling available to a normal smith's shop, there is a point of diminishing returns for the smallest grain size that you can get that occurs about three cycles. Unless you move in the direction of really good thermal controls, three cycles is about as small as the grain will get before the next cycle increases the size only to reduce the size to where you were before.
 
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