blade quench stress- extreme example

Kevin McGovern

Kevin McGovern

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Jul 31, 2015
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I was just checking out this video of the making of a Japanese style sword blade. The coolest part was the brine quench in a fish tank. I knew the blade would bend, but had no idea it bent this much. Jump to 12:09 for the acrobatic steel movement.

[youtube]Q598DP27tGA[/youtube]
 
On top of the brine quench, it seems like whenever they do a Katana, they never show any tempering stage. Did they not temper the Katanas? Technically, the steel should be auto-tempered to a certain degree but definitely nowhere near the multiple cycles at X hours at exact temperature that most bladesmiths put their blades through.
 
That's cool.
I'm trying my first brine quench tonight on some w2 to try to get a better hamon.
 
If the do the same thing as the kitchen knife guys do then they probably go back to the forge and heat the blade to where when they sprinkle water on it, it dances around in a certain manner. Murray Carter is the only Japanese trained smith that I have actually seen demonstrate that on video, but he is not nearly as secretive as some of those guys. There is an old legend about a Japanese swordsmith who chopped of an apprentice's hand because he had the temerity to stick his fingers in the quench tank to find out how warm the water was. :eek:
duurza said:
On top of the brine quench, it seems like whenever they do a Katana, they never show any tempering stage. Did they not temper the Katanas? Technically, the steel should be auto-tempered to a certain degree but definitely nowhere near the multiple cycles at X hours at exact temperature that most bladesmiths put their blades through.
Click to expand...
 
It would be interesting to me to study this process and what is actually happening. I know that when you heat steel to the plastic stage and let it cool unevenly the steel can change shape and it will also develop residual stresses internally- part of the cross section will be in tension and part will be in compression. Taken to an extreme this is what causes the sword to change shape. (As I understand this is how they create tempered glass and the reason it behaves as it does when it breaks.)

As an engineer I have studied what this uneven cooling does to structural steel shapes and how it affects the behavior of the steel when loaded in a building for instance. And in this case it is a bit detrimental to the strength of a building. I haven't studied what it does to a blade.
 
bdmicarta said:
It would be interesting to me to study this process and what is actually happening. I know that when you heat steel to the plastic stage and let it cool unevenly the steel can change shape and it will also develop residual stresses internally- part of the cross section will be in tension and part will be in compression. Taken to an extreme this is what causes the sword to change shape. (As I understand this is how they create tempered glass and the reason it behaves as it does when it breaks.)

As an engineer I have studied what this uneven cooling does to structural steel shapes and how it affects the behavior of the steel when loaded in a building for instance. And in this case it is a bit detrimental to the strength of a building. I haven't studied what it does to a blade.
Click to expand...

It's explained in here:

http://www.hybridburners.com/documents/verhoeven.pdf
 
kdogmcg said:
I was just checking out this video of the making of a Japanese style sword blade. The coolest part was the brine quench in a fish tank. I knew the blade would bend, but had no idea it bent this much. Jump to 12:09 for the acrobatic steel movement.

[youtube]Q598DP27tGA[/youtube]
Click to expand...

I dont have any sound on my work computer so I'm not sure if there is a narrative
but do you that it is a brine? or is it straight water?

Harbeer
 
It's not only cooling but also transformation to martensite. Repeating what I have said in the past - I would never try to predict the changes during quenching of the sword . Remember the guy nwho wondered what would happen with an oil quench ? The blade curved the other way !!!
 
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