Quenching a Knife in Liquid Nitrogen! Will it survive?

[KnifeSteelNerds]

Thanks for inviting me on to talk about quenching!

[bschneidez]

Bro, you could afford a mansion if you start selling liquid nitrogen quenched katanas to mall ninjas for way too much money 🤣

[the_omg]

Couple of comments: Oil quench tanks normally have a lot of circulation to help with the heat transfer. The first quench in that steel tube was horrible and didn't get anywhere near its potential hardness.
Second, you should always do a light surface grind or at least clean up the part with emery paper before hardness testing. You'll always get a bit of surface decarburization that will affect your test results. (even with a neutral atmosphere furnace)

The nitrogen quench didn't work the way you expected because all it did was vaporize the nitrogen near the hot steel so in effect all you got was a frigid air quench with splashes of LN2. If you put it into a very fast stream of LN2 so that it could carry away the heat before it vaporized you might get the cooling you expect, but I doubt if the knife would survive intact.

[bgd]

amazing subject. I took on automotive chores welding in 2006. I keep my own unwritten book in my head about quenching. you don't know what you made, until a whole year has gone to meet the day you made it.

[jagoq]

As a knife maker and a musician, I was really interested in the differing tones the three methods produced, when dropped 😀

[senfdame]

Nate: Drops knifes to see if they break

Also Nate: Wears Safety Glasses on his head

[Joseph_Streubel]

Nate, great video! Being in the heat treat industry, I was surprised to not see the knife crack in half while in nitrogen quench.

[zacharyreid]

i miss nate’s TKOR days but i’m glad to see he is doing so well for himself

[thenotsurechannel]

06:30 You forgot to show us the results of the nitrogen quenched blade.

[matthiasbaumbach]

Best part of the video is the visualisation of the Leidenfrost-effect during the first nitrogen quenching. You can see that metal cools down slowlier despite the extreme cold nitrogen, because of this effect. The effect in short is that the difference in temperature is so high that the liquid immediately boils. Thus there constantly is a layer of nitrogen gas between the metal and the liquid nitrogen which acts as an thermal insulator, slowing down the cooling process.
A really cool video, thanks!

[brigzy]

I'm so glad you're doing well on YouTube, TKOR don't know what they've lost

[MisterRorschach]

This is my favorite type of video.
The kind where I see the title and thumbnail and say “that’s stupid”
And then say, “but I’m gonna watch it anyway”.

[t.b.a.r.r.o.]

Pro tip...
When hardness testing thinnish pieces, use a small diameter anvil to avoid a possible warp in the piece from introducing error due to flexing when the test load is applied.

[BarnyTrubble]

1. I love that the liquid nitrogen was conspicuously absent from the first round of hardness testing
2. We got confirmation that it did, indeed, produce the hardest knife, despite being conspicuously excluded
3. We got an explanation as to why it would perform the best, because of how quickly it cooled the metal (to grossly oversimplify)

[BjrnJacobsen]

Every professional I've talked to has always told me that hardening in oil hardens the steel better than in water because it adds carbon to the steel and makes it more elastic so it doesn't become as brittle. Therefore, it is not only about how hard you want the steel, but also about which property you want. For example, you want a hammer to be very hard, but also elastic, so that it does not splinter when you hit it. I use the word hardening, because that's what it's called in Danish.

[gonnabeadoctorsoon]

So Nate, as a blacksmith my only issue with your video is that you left the scale from heat treat on the surface of the knives. This dramatically changes what hardness the metal is actually at. Your tester was testing the oxide layer on the metal, not the metal. You should grind to shiny clean metal for hardness testing.

The weird colors on the nitrogen quench were actually tempering colors caused by the weird cooling the vapor jacket allowed. The vapor jacket was preventing the liquid contact, as you stated, and since there was no heat exchange with the nitrogen, the metal reheated changing its temper. Each time the nitrogen made contact, it cooled it until the vapor prevented heat transfer. The metal would then reheat in a slightly different area, changing temper again.

[DH-xwjp]

Nate's thoughts: huh, i need some new steak knives...

Also Nate: *[light bulb dings]* knife video!

[jk]

As a gynecologist I can tell you this. Quenching anything but your thirst in liquid nitrogen is a big mistake. 🧨

[meganw]

(5:05) Check out how much the liquid Nitrogen level goes down during that quench; how much evaporated off over the process of adding so much heat to it

[NUCLEARxREDACTED]

Wow havent visited this channel for a bit and I come back to 200k subscribers and a video with close to 400 thousand views in only 2 days. Thats absolutely fantastic, this channel really deserves it.