Magnacut Cryo Time

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Mobius1

Joined
Feb 15, 2016
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Has anyone done any testing on this? The article says 4 hours, but I tend to only cryo for 30 minutes.

To quote Roman Landes, "Extensive soak time is not necessary since the process runs at hyper sonic speed." He recommended 30 minute soak in liquid nitrogen for 3v, and that statement has always stuck with me.

I plan to do some interrupted oil quench testing that I will post about, but I want to get my heat treat plan down.

The current plan is:

Stress Relief - 1300F for 2 hours, oven cool overnight.

Max ramp speed to 1600F, placing knives in oven at 1200F (so the blade coating properly bakes.), hold at 1600 for 30 minutes for preheat.

Max ramp to 2050F, hold 20 minutes, quench in oil, interrupting at 1000F. Oil will be between 150 and 175F (I will be using Citgo Quenchol 521, a 15 second oil I believe.)

Air cool to (near) room temperature, then soak in LN2 for 30 minutes.

2 hour temper at 300F, quench in water, then soak in LN2 for another 30 minutes

2 hour temper at 350F, quench in water, then repeat for a 3rd 30 minute cryo and 350F temper (I know this 3rd cycle is probably a waste of time but it's a habit I think many of us can't let go, in fact I think some do 4!! :D)

I'm debating a 1 hour cryo, but 4 is just so long to try and fit in!
 
Geez, am I crazy? I could have sworn I read it should have a 4 hour cryo somewhere. Which I thought sounded excessive!

So I guess I won't worry too much about my cryo soak time, then.

I ordered some ATP-641 to compare to Condursal Z-1100, since it is rated at 2400F as opposed to latter which is 2013F, so I should be able to oil quench MagnaCut one way or another. I'll hopefully get the quench time pegged after some testing this evening. Then I will do a few coupons to test and compare with plate quenched.

Thus far I have had varied results with plate quenching MC, getting RC readings of 61-63, even on different spots of the same knife. I'm not sure what is causing these inconsistencies. My goal with the oil quenching is to be able to grind bevels before the quench, and perhaps get more consistent numbers. My oven is an Evenheat LB, so I don't think it has temperature issues. I'm wondering if it has something to do with the way I apply compressed air during the quench (I just use a typical air compressor blow gun), since I am not exactly consistent on how I blow it through the plates. If that's the case, or if it's being caused by something else, my oil quenching results should help me narrow it down.
 
I don't have any memory of recommending, or even mentioning, a 4 hour cryo for any steel, ever.
 
Mobius1 said:
Thus far I have had varied results with plate quenching MC, getting RC readings of 61-63, even on different spots of the same knife. I'm not sure what is causing these inconsistencies. My goal with the oil quenching is to be able to grind bevels before the quench, and perhaps get more consistent numbers. My oven is an Evenheat LB, so I don't think it has temperature issues. I'm wondering if it has something to do with the way I apply compressed air during the quench (I just use a typical air compressor blow gun), since I am not exactly consistent on how I blow it through the plates. If that's the case, or if it's being caused by something else, my oil quenching results should help me narrow it down.
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More likely it is inconsistency from surface finish, flatness, etc. And remember there will always be some variance between tests.
 
Larrin said:
I don't have any memory of recommending, or even mentioning, a 4 hour cryo for any steel, ever.
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Awesome! Thanks for the response!
Larrin said:
y from surface finish, flatness, etc. And remember there will always be some variance between tests.
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If only I had more MagnaCut to test!! :D

I plan to use up to 6 test coupons, though I will start with just 3. I'll take them through the full heat treat and then test their Rockwell.

As I've stated in another thread, my reason for oil quenching is not because I hope to get better results, but because I prefer grinding my bevels pre-heat treat, and I do a lot of saber grinds.
 
I don't think you're going to have great results using ATP on stainless steels. I found that while it is rated for 2300°F (or 2400°F), the closer you get to that temperature, the more decarb you will have. It works very well on carbon steel that is hardened at 1500°F, but I noticed a little more decarb with A2, a little more with D2, and even more with AEBL/CPM154. Of course, this isn't too big of a problem if you have enough steel to grind away that decarb later.
When I switched to the stainless foil, no more decarb. Sometimes the foil works so well it almost welds itself to the steel.

Another thing, if you're grinding your bevels pre heat treat and plan on oil quench, depending on how thin your edge is, it might "bacon" warp on you!
 
Thanks for the heads up! I'm hoping the Condursal holds up pretty well. I know it does 1950F well, because that's what I usually work at. I have read on a spec sheet that it can handle two coats, so I may even try that. Otherwise, the MagnaCut stock I have is .182" so I have a lot of room!

I've actually thought of doing a test to see if oil quenching with steel foil on also has much impact on cooling speed, as that is another option.

I've never had issues with warping, but my thin edges tend to be 4 inches or less in length. But I've always found that with a proper stress relief, warping isn't an issue for me. That is, with my 3v oil quenching experience.

And actually, I just thought of another question about MagnaCut. On my Puukkos I like to peen the tang, which you can't do on air hardening steels without a little persuasion. Currently what I do is heat the end with a torch so that it is just dull red, no hotter, and hold it there for a minute or two, and then quench in water once it cools to black. I am hoping this technique will also work on MagnaCut as it did with 3v and Z-Wear?
 
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