Recommendation? Hybrid Quenching... Water, then Oil?

[Kentucky]

Ive water quenched quit a bit. Yes Ive lost a few but overall it was easily worth it.. Leave the edge a little thick, make sure your water or brine is right and leave out a tiny glass of good bourbon for the Tink fairy..

 

[kuraki]

Water quench pulls the edge apart, oil quench pulls the spine apart. In my experience anyway.

Well, I was in the water briefly, felt/heard nothing, and in the oil felt and heard that distinct tink. This was the only crack.

 

[Willie71]

Well, I was in the water briefly, felt/heard nothing, and in the oil felt and heard that distinct tink. This was the only crack.

Yes, the stress from whe water quench initiated the crack, then the oil propagated it. If only oil, probably wouldn’t have happened that way, or not at all. You have to think where the steel is going square, trapezoidal, then square again. It doesn’t happen evenly.

 

[olymon]

kuraki, I wonder if a nice smooth edge would have made a difference. I know the scratches from grinding the blade left a streess riser. Maybe sand round or stone the edge? No real idea on my part just an observation.

 

[Jesse WW]

So i gave it a shot. Thought it was a success until i gave the blade a clean! I quenched in the brine 3 seconds followed by quenching in the oil until the blade cooled down completely. Maybe i should try quenching in the brine for 1-2 seconds next time? Both the brine and oil were at room temp.

 

[Willie71]

So i gave it a shot. Thought it was a success until i gave the blade a clean! I quenched in the brine 3 seconds followed by quenching in the oil until the blade cooled down completely. Maybe i should try quenching in the brine for 1-2 seconds next time? Both the brine and oil were at room temp.

Try going to a finer belt before quench. A few passes lengthwise along the blade and spine reduce stress risers too.

 

[jdm61]

I saw a post he made a few years back about how he quenches his katanas and he said 2-3 seconds in 120F water and then into the canola oil.

Walter Sorrels does it all the time. I've done it a few times without problem

 

[Ian Fifelski]

I really want to try the oil over water quench. Should I give it a go? What was the answer to that question?

 

[Natlek]

Yep, have wondered about the same thing myself.
But the blade receiving the oil first would seem counterintuitive I would think? Why have the slow quench go before the fast one? Shouldn’t it be the other way around? So the surface of the steel receives faster cooling followed by the internal part cooling slower?

Doable ...............but only one knife at time

 

[john april]

i do not have an answer, but it coulden't hurt to try. maybe a half second in the oil and then down into the brine for 3 seconds then back up into the oil ? there may be something to gain ( or lose?) by having no interruptions between oil/water/oil

 

[stezann]

It is pointless starting into oil and then switching into water.
Shallow hardening steels have the problem they need to be cooled under 900 °F (pass the nose) in very short time, something within 1 second frame.
That is the critical step; after this the only requirement it is that the cooling has to be continuous until Mf. By continuous i don't mean constant rate, but just straight way down without reheating. The time frame of this continuous cooling doesn't call for shear speed, and any excess it's undue stress where eveness it is the only requirement.
It is the first stage where most oils fall short; it is the second stage where water is overlay excess.
By the way, the need for the second stage into oil (for hypereutectoids) is just because the red heat in the clayied spine needs to be removed before it bleeds into the martensite edge enough to overtemper it, otherwise the continuous cooling could be also air cooling.

 

[Jesenius]

Critical temperature when quenching steel is cca 300°C (cca 570F). Over this point should be fast and under this point should be slow. You can try this: When You drop Your blade into water You'll see how it change color from hot red to black. When it get black (cca 450°C) then take it out and cool on air or in oil. Or You can try quench in quenching polymers. Its quenching speed is something between water and oil.

 

[stezann]

Hi Jesenius, the critical point you are talking about is Ms, the one i am talking about is in correspondance with the nose of the cooling curve, where the faster quenchants exert their effects. Under this temperature, any oil quenchant is going to work.
Under the nose you get more time for your cooling in which you still stay on the left of the curve (where only martensite is about to form).
As soon as Ms begin, the time frame gets further increased and as you cool down martensite replaces the supercooled austenite. This is the zone where eveness of cooling matters the most and where the delta T°F from core to surface of the piece can do the damages, as you very correctly underlined. A bit of warning, hypoeutectoid steels usually have Ms fairly over desired tempering temperature, so air cooling from Ms is not advisable as you overtemper the martensite as it forms. On the other hand hypereutectoid steels have their Ms at 400-450 °F, so even air cooling in that range doesn't compromise the heat treatment. Marquenching takes advantage from this property of hypereutectoid steels, but it is not suitable for hypoeutectoid steels.
I mean, as Ms approaches, shallow hardening steels don't behave any different from deeper hardening steels, but the initial phase of cooling requires a faster - than ordinary oil - quenchant to begin with, so the interrupted sequence oil-water-oil doesn't make any sense, whereas water-oil does....in case one lacks Parks#50 or the like.

 

[Jesenius]

Thank You for explanation. I just used information from material spec in combination of some info from our local knife forum. Not used exact terms because of My poor language skills.

 

[stezann]

Actually your explanation is correct, and the transformation temperature range you pointed out (Ms: Martensite start....Mf: martensite finish) is where the dreaded "ping" lurks; i just felt to dig further into the subject trying to focus on the bases of hybrid quenches.

 

[Teppojutsu]

i have thought of that same thing steve, if it goes through the oil before the water, it will not receive as much as a shock from just doing water. curious what others think.

This is aslo something that i was thinking about.
Made sense to me as well
Edit to add but i guess not so much

 

[olymon]

OK, who's going to get real crazy and mix up a block of cold Knox gelatin and float that on top of some oil and then quench through that.

 

[Ian Fifelski]

It is pointless starting into oil and then switching into water.
Shallow hardening steels have the problem they need to be cooled under 900 °F (pass the nose) in very short time, something within 1 second frame.
That is the critical step; after this the only requirement it is that the cooling has to be continuous until Mf. By continuous i don't mean constant rate, but just straight way down without reheating. The time frame of this continuous cooling doesn't call for shear speed, and any excess it's undue stress where eveness it is the only requirement.
It is the first stage where most oils fall short; it is the second stage where water is overlay excess.
By the way, the need for the second stage into oil (for hypereutectoids) is just because the red heat in the clayied spine needs to be removed before it bleeds into the martensite edge enough to overtemper it, otherwise the continuous cooling could be also air cooling.

I believe that this would be used for steels that crack in water. So the oil would reduce the 'impact' of water for steels like 1075. I think this would be a good method for a hamon because it would cool quickly but avoid the cracking. If I were to use an oil then water method I would do it for a better hamon activity and would pretty much go directly from the oil into the water; not even a seconds time.

Hey, I am relatively new at this (knifemaking) but I think this makes sense?

 

[Teppojutsu]

This is kinda where i was at thinking the best hamon activities came out in the violence of the quench.
Thats why i thought people used parks 50 was becase it was a "fast" oil but more gentle than plain water .

So i figured a layer of oil to just take a tad bit of stress before the water.

Also has anyone heated their oil (being careful of flashpoint) to make the viscosity more like water?

 

[Ian Fifelski]

Also has anyone heated their oil (being careful of flashpoint) to make the viscosity more like water?

Do you mean for heating parks 50?

I heat canola every time I use it. Cold canola won't harden steel very well at all.