Oil quenching AEB-L

[_Dan_]

Okay. I'll do that next time. I remember reading to do it somewhere, but don't remember where. Lots of older AEB-L information out there, and I'll bet some of it is outdated practice. Does preheating put too much carbon into solution?

He's correct there. I was going to say this.

No it doesn't it's just not necessary whatsoever on something as thin as a knife. Neither is 60 mins at -10, 30 should be fine but 60 may be excessive if you need to save time and tempering as soon as possible -- basically all as one "heat treatment motion" is the best way to think about it in my opinion.

 

[Seedy Lot]

With foil decarb is about zero.

I have tried NoScale with lower alloy steels and have had mixed results as I still had to grind through decarb to get to good steel for hardness testing. This was with lower austenitizing temps so I would expect more decarb with the higher oven temps required for AEBL. If your steel is thick enough I imagine you can grind through the crap steel to get to the goods hidden within.

With 1950 austenitizing and a freezer for cold treatment the retaiend austenite is creeping up. In Larrin's book he recommends using 1925 oven temp when not using cryo.

 

[Bühlmann]

How would I be getting Tsubosan files to skate at 60+ if the anti-scale didn’t work? Wouldn’t they drag on the decarb? The only prep I did out of HT was to remove the residual surface black with some 120, 220, and 400 grit paper by hand. Took less than 5 minutes for the entire blade.

 

[_Dan_]

How would I be getting Tsubosan files to skate at 60+ if the anti-scale didn’t work? Wouldn’t they drag on the decarb? The only prep I did out of HT was to remove the residual surface black with some 120, 220, and 400 grit paper by hand. Took less than 5 minutes for the entire blade.

Decarb is white not black*...

I can't say without imaging..

Edit: my best guess without imaging is that propane burns at ~3600F and that destroyed the nuclayer layer. Foil is more expensive but heat treatment in a forge - I can't say which one is better won't pretend to.

 

[Bühlmann]

I think the black was the residue left from the NoScale 2000 doing its job. It leaves low alloy blades a nice black out of the oil, too. The clay mostly comes off in the oil, leaving a blackened surface. May be the oil doing the blackening, but either way I’m not seeing evidence of a decarb layer. If there was one, it was super thin and easily removed with minimal hand sanding.

I’m not a smart man, but if I were to hazard a guess the 2000 in “NoScale 2000” is an effective temperature rating. That makes sense to me, but is still an assumption. Could just be the year he developed it, or the year he got married, IDK.

I don’t have any interest or motivation to argue any of this as being “right”. I’m just telling you what I did and the results I got with the materials & procedures I used. But I’m happy to discuss and learn hows & whys this non-standard method may or may not have been successful.

 

[Bühlmann]

Decarb is white not black*...

I can't say without imaging..

Edit: my best guess without imaging is that propane burns at ~3600F and that destroyed the nuclayer layer. Foil is more expensive but heat treatment in a forge - I can't say which one is better won't pretend to.

This wasn’t HT’d in a forge. It was done in a Jen-Ken AirBath kiln.

 

[Joshua Fisher]

Just to jump in with my experience using noscale 2000, it is named that because that’s the temp it was tested up to and known to work. I tried it on some magnacut at 2050F and it burnt and decarbed heavily, it’s very easy to see if it failed it looks like burnt steel. I use noscale 2000 on nitro-v that I heat to 1900 with no pre-soak and oil quench and have not had issues with decarb. You can clamp in plates after a short quench to help keep things straight but I’ve had pieces warp back in the temper or after being taken out of plates so I don’t worry about it and just fix any warps with a carbide hammer after temper.

 

[_Dan_]

This wasn’t HT’d in a forge. It was done in a Jen-Ken AirBath kiln.

My bad I can't read apparently lol.

Just to jump in with my experience using noscale 2000, it is named that because that’s the temp it was tested up to and known to work. I tried it on some magnacut at 2050F and it burnt and decarbed heavily, it’s very easy to see if it failed it looks like burnt steel. I use noscale 2000 on nitro-v that I heat to 1900 with no pre-soak and oil quench and have not had issues with decarb. You can clamp in plates after a short quench to help keep things straight but I’ve had pieces warp back in the temper or after being taken out of plates so I don’t worry about it and just fix any warps with a carbide hammer after temper.

Thanks for the experience Joshua Fisher

I don't have any experience with this nuclayer stuff - but a general is if you are HTing in a furnace yes use foil. AISI 309 or 321 depending on what alloy you are doing. Always use foil.

 

[_Dan_]

I think the black was the residue left from the NoScale 2000 doing its job. It leaves low alloy blades a nice black out of the oil, too. The clay mostly comes off in the oil, leaving a blackened surface. May be the oil doing the blackening, but either way I’m not seeing evidence of a decarb layer. If there was one, it was super thin and easily removed with minimal hand sanding.

I’m not a smart man, but if I were to hazard a guess the 2000 in “NoScale 2000” is an effective temperature rating. That makes sense to me, but is still an assumption. Could just be the year he developed it, or the year he got married, IDK.

I don’t have any interest or motivation to argue any of this as being “right”. I’m just telling you what I did and the results I got with the materials & procedures I used. But I’m happy to discuss and learn hows & whys this non-standard method may or may not have been successful.

Yes also they'll say that 309 is fine to 2200/1200c which it isn't. 321 is around 2k. And properly heat treated you should not see any discoloration upon a break like that. Something is reacting chemically.

 

[Bühlmann]

Just to jump in with my experience using noscale 2000, it is named that because that’s the temp it was tested up to and known to work. I tried it on some magnacut at 2050F and it burnt and decarbed heavily, it’s very easy to see if it failed it looks like burnt steel. I use noscale 2000 on nitro-v that I heat to 1900 with no pre-soak and oil quench and have not had issues with decarb. You can clamp in plates after a short quench to help keep things straight but I’ve had pieces warp back in the temper or after being taken out of plates so I don’t worry about it and just fix any warps with a carbide hammer after temper.

Thank you Josh! That seems to mirror what my experience has been.

On a side note, I did get a chance to use your sweet little carbide hammer on this project and it worked like magic! I checked for straightness between temper cycles and there was just the smallest bend, so I gave it a few taps on the offending side and checked, few more taps, checked, a few final taps and it laid perfectly flat on the glass plate I use to check stuff. Thank you for offering those up.

 

[Bühlmann]

Yes also they'll say that 309 is fine to 2200/1200c which it isn't. 321 is around 2k. And properly heat treated you should not see any discoloration upon a break like that. Something is reacting chemically.

Did you read the part where I mentioned that I didn't put the anti-scale on the edges of the coupon? Not sure if that would do it, but in my mind that would be very similar to not sealing up a foil pack.

I think the dark bands on the test piece are decarb (?) where I didn't apply the NuClayer 2000 to the edges of the scrap piece, only the flats. That is interesting. The blade got the full application of anti-scale.

 

[Joshua Fisher]

Thank you Josh! That seems to mirror what my experience has been.

On a side note, I did get a chance to use your sweet little carbide hammer on this project and it worked like magic! I checked for straightness between temper cycles and there was just the smallest bend, so I gave it a few taps on the offending side and checked, few more taps, checked, a few final taps and it laid perfectly flat on the glass plate I use to check stuff. Thank you for offering those up.

Glad to hear it’s working well for you, it’s such a big time saver in my shop. Outside of breaking and checking sample is definitely recommend some practical testing, see how your edge retention is for a given geometry and test corrosion resistance in use, then they some practical abusive tests. For example for edge retention I make a sample kitchen knife because I can prioritize the best cutting geometry, I make any sample knife for testing different steels the same geometry. 005-.010 behind the edge before sharpening, usually I’m right in the middle of that range. Sharpened to the same degree for each knife, I prefer to hand sharpen and will set my edge with a 200 grit stone and finish on a 1000 then strop. For the test itself I cut 1/2” sisal rope that I can get from the hardware store on a end grain cutting board until the knife will no long cut paper at all and record the number of cuts, I check every 100 cuts for simplicity. You can repeat that test on any steel to get an idea of how well the steel holds that edge. As a example of two steels I’ve tested I got 1900 cuts with a Apex ultra knife at 65-66rc and got 2900 cuts with a nitro-v knife at 62rc. After that I’ll see if I can strop the edge back to 100% or if I have to use a stone to resharpen, nitro-v passed the strop test ApexUltra did not. That helps me determine the edge stability at that given geometry, the apex knife likely had some micro chipping that wouldn’t strop out. Then I’ll test the knife in real use in my kitchen for a while to see how the corrosion resistance is for stainless. If I’m satisfied with both of those tests then I’ll make a sample for destruction testing with a bit thicker geometry, try chopping practical objects or brass rods, test the tip bending or prying and ultimately test how much it takes to break the knife. Lab tests are great but keep in mind knives aren’t being used in labs and doing practical testing is a great way to see how different steels perform relative to each other and how you can expect them to hold up to the end user.

 

[_Dan_]

Did you read the part where I mentioned that I didn't put the anti-scale on the edges of the coupon? Not sure if that would do it, but in my mind that would be very similar to not sealing up a foil pack.

No but I figured it out and no that doesn't account for it. It would be black on the outside not the inside...

Also carbide hammer fixing is not ideal for the microstructure and any possible edge or screw dislocations

Edit: for the above, heating to 400F may lessen any problems or it can create more. It really depends on a lot of factors all of which I can't list here. I'm not saying that it doesn't work. It does, it just has the potential to make.. negative things more of a problem so I don't personally do the carbide banana up technique.