oil quenching d2 to reduce austintite and refine grain

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clockworkfish

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Dec 1, 2010
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Right off the bat i know some of you will think that this is a bad idea, but is there a way to reduce the likelihood of cracking and warping d2 blades in an oil quench? from what i have read it seems as if an oil quench plus a liquid nitrogen treatment will get the steel to near full martinsite as well as reducing the grain of the steel, which if my understanding of heat treating is right, would produce an ideal blade. http://books.google.com/books?id=cY...0CDwQ6AEwAQ#v=onepage&q=d2 oil quench&f=false on pages 238-242 this is discussed, though no mention of what type of quenching oil is used is brought up and i am figuring that this type of research is aimed more for the tool and die makers using d2 rather than us knife-makers.

In another book http://books.google.com/books?id=bo...0CGMQ6AEwBg#v=onepage&q=d2 oil quench&f=false on pages 560 to 565 they compare different methods of heat treating d2 side by side and again it seems as if oil quenching and liquid nitrogen provide very desirable results.


So as knife-makers how could we reduce the negative effects of oil quenching in order to reap the benefits? or is this kind of quenching much like quenching 1095 in water which i know first hand is a 50/50 shot in the dark of success or failure.

-what would be the ideal oil
-i assume turco (spelling?) would be needed to be applied to the blade or could something like a thin layer of refractory cement be applied?
-are there any methods of reducing warping that could be used?
-What is the likely hood of failure by using an oil quench?


Thanks for reading and i hope somebody can provide some decent answers
 
This is the reason for plate quenching between cold aluminum plates. Otherwise, I'd say get the slowest oil you can find. Hopefully Nathan the Machinist will chime in. His D2 blades don't appear to show an advantage when cold treated, in his testing. He's done a lot of work with D2.

Steels like this are typically austenized in a controlled atmosphere furnace or vacuum furnace. Stainless foil wraps are also used. I assume Turco is a surface protecting coating. It's temperature limits would need to be checked.

I'm not sure the above treatments will reduce the grain size, but they will definately reduce the %RA. It's interesting the refrigeration treatment alone reduced the D2 %RA to a lower amount than A2.
 
Turco won't work above 1500F, so it won't work for D-2. A plate quench and then oil quench after 10 seconds would be your best procedure if you are determined to do that, but I don't know if you will gain anything.

D-2 will be all it can be if you:
austenitized for 30 minutes in a controlled oven and in a foil packet at 1950F
plate quenched to ambient
snap temper at 300F for 30 minutes
cool to ambient
cryo for 2-4 hours
temper twice at 1000F
 
bladsmth said:
Turco won't work above 1500F, so it won't work for D-2. A plate quench and then oil quench after 10 seconds would be your best procedure if you are determined to do that, but I don't know if you will gain anything.

D-2 will be all it can be if you:
austenitized for 30 minutes in a controlled oven and in a foil packet at 1950F
plate quenched to ambient
snap temper at 300F for 30 minutes
cool to ambient
cryo for 2-4 hours
temper twice at 1000F
Click to expand...

what is this snap tempering that i keep hearing people mention all about? like how is it done? is it just a temper at 300F immediately after the quench? also when the metal is cooled to ambient how long can you wait before cryo happens? same goes for tempering after cryo?
 
Why so much higher than that used in the study for austenizing? This is the 2nd study I've read where air hardening steels were oil quenched. It makes comparisons for people who do air quench a little troublesome.

A snap temper is a temper cycle just high enough to relieve a little stress and not really affect hardness. It reduces the chance of cracking when you put a freshly quenched room temperature part into something that is 200 to 300 degrees colder. Cryo is generally best done immediately after the quench, but if cracking is or could be a problem, a snap temper is done first. Tempering after cryo is done after the part is brought back to room temperature naturally. At least I've never heard of anyone rushing it by putting it in an oven straight out of LN2.
 
Brownells sells an anti-scale compound for higher temps.
bladsmth said:
Turco won't work above 1500F, so it won't work for D-2. A plate quench and then oil quench after 10 seconds would be your best procedure if you are determined to do that, but I don't know if you will gain anything.

D-2 will be all it can be if you:
austenitized for 30 minutes in a controlled oven and in a foil packet at 1950F
plate quenched to ambient
snap temper at 300F for 30 minutes
cool to ambient
cryo for 2-4 hours
temper twice at 1000F
Click to expand...
 
me2 said:
Hopefully Nathan the Machinist will chime in. His D2 blades don't appear to show an advantage when cold treated, in his testing. He's done a lot of work with D2.
.
Click to expand...

I think if you check Nathan is a believer in cold treatment. You may be referring to not much difference between full blown cyro with liquid nitrogen over the simpler dry ice/acetone method.
 
Oh. I thought he said he didn't see much benefit for his D2 blades. Maybe I misread him.
 
Cold treatments don't in any way effect grain size !!! That's more a function of the austenitic grain size before quenching. That grain size is going to be made by the temperature .These high alloy stainless steels will require you to compromise .Higher temperatures => larger grains, more retained austenite.So , within the normal range decide what you want .
[[Then you could pick a better steel than D2 !]] I had to say that , sorry.
Never use cryo to make up for poor HT !!
 
cold treat itself does not refine the grain i believe. it can be refined by reaustenize a cold treated steel using induction furance or lead bath, basically it has to be done by a fast heat rate. the reason cause this refinement is more sites of nuclearation after deep cyro. supposely, some supperfine carbides will form during the deep cyro, thus acting as more sites of nuclearation. deep cyro cause a nearly complete transform of RA. thus the following induction charge will have much lower chance to triggle the grain "inheirtage".

btw, the stuff i typed above was not tested or examed by myself, it was from some papper i readed years ago... it was wrote in a viking rune like texts, i had to online translated it into english... so don't take what i just said as reference.
 
On of the forumites pointed out that I typed the order backward for the oil and plate quench. If you were to do both, you would oil quench and then plate quench. I personally just air quench using the plates.
He says he uses D-2 and does not recommend a snap temper or cryo. I have read it both ways, but will defer to his current experience.

The numbers I posted were for an air quench followed by cryo and a high range temper . This was to increase hardness and toughness. If you did an oil quench, you would want to austenitize at 1850F. Many temper in the lower range between 400F and 500F.

I would like to elaborate on my comments about D-2.
When I said it would be all it could be ...... I meant that it may never be all that great a knife. Sure it is hard and tough, but I don't really consider it a superb knife steel. There are many other good knife steels that are hard and tough. Steels like CPM3V and others may well be better choices. I don't use D-2 any more, and have switched to mainly S35VN for any non-forged blades.
 
bladsmth said:
When I said it would be all it could be ......
Click to expand...

I agree. D2 makes a good blade, not superb by 21st-century standards. But if you really want to get serious about fine grain and small carbides, there are many better choices. For instance, I haven't found D2 to be any tougher or hold an edge any longer than CPM-154, and CPM-154 is a lot prettier with better corrosion resistance, and much easier to get a really fine edge on. .

ETA: It may be worth mentioning that there's a powder version, CPM-D2. In theory that should have finer grain and more evenly-dispersed, if not actually smaller carbides. It definitely polishes up better, but I haven't tested it enough to say whether it's any tougher or holds an edge better than "regular" D2.
 
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james terrio said:
I agree. D2 makes a good blade, not superb by 21st-century standards. But if you really want to get serious about fine grain and small carbides, there are many better choices. For instance, I haven't found D2 to be any tougher or hold an edge any longer than CPM-154, and CPM-154 is a lot prettier with better corrosion resistance, and much easier to get a really fine edge on. .

ETA: It may be worth mentioning that there's a powder version, CPM-D2. In theory that should have finer grain and more evenly-dispersed, if not actually smaller carbides. It definitely polishes up better, but I haven't tested it enough to say whether it's any tougher or holds an edge better than "regular" D2.
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From what I have been reading on the forums cpm d2 is just as good as many modern steels and I didn't mean to say that cryo would reduce grain size, but wouldn't the oil quench as grain refinement (as far as I know) comes from just how rapidly the steel is quenched. I am mostly curious about the oil quench as it sees to be better and less expensive to start than plate quenching.
 
I'm pretty sure troubles with grain size come mostly from overheating before quench. I don't know if a faster quench would help correct that, but I don't think so.
 
james terrio said:
I'm pretty sure troubles with grain size come mostly from overheating before quench. I don't know if a faster quench would help correct that, but I don't think so.
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Right but assuming that it was quenched at the proper temp wouldn't the faster quench shock the metal and this reduce the grain size somewhat?
 
clockworkfish said:
Right but assuming that it was quenched at the proper temp wouldn't the faster quench shock the metal and this reduce the grain size somewhat?
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I'm getting a little out of my depth here, but again, I don't think the quench medium is going to influence grain size. "Shocking" the metal is probably the last thing you'd want to do.

As for the cost of oil vs. plates... you buy plates once and they don't change. Good profesional quenchants are pricy and have their own maintenance requirements. If you're thinking of quenching high-alloy steel in canola or used motor oil to save money, I think you're barking up the wrong tree completely.
Not to flog a dead horse, but if you want really fine grain and small carbides, D2 is not your best option anyway. I will defer now to Stacy, mete, and Nathan, who all know a helluva lot more about HT than I do.
 
bladsmth said:
Turco won't work above 1500F
Click to expand...

Turco's not available anymore.

There's an intriguing chart in the ASM Heat Treater's Guide that shows a radical grain size reduction with a dual quench with reducing temperatures. I'm at work and can't look it up right now, but they reference a technical paper from one of the defense contractors who did extensive studies on the initial austentizing temperature, the secondary austentizing temperature, and the resulting grain size.

As far as Cryo, the austentizing temperature determines how much retained austenite you have, and therefore whether you'll see any benefit from sub-zero treatment.

I seem to remember reading that Bob Dozier doesn't do cryo.
 
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The grain size is determined by the maximum heat and time at that heat. The speed of the quench just locks it in. It doesn't reduce it.
 
lazlo said:
There's an intriguing chart in the ASM Heat Treater's Guide that shows a radical grain size reduction with a dual quench with reducing temperatures.
Click to expand...

I just realized your second link was to an online version of the ASM Heat Treater's Guide. This is the chart I was talking about. "Prequenching" is the industry term for a double-quench.
Has anyone tried this?

D2prequench.jpg
 
I have done that. And, looking at broken test coupons, it appears to my eye that it does reduce grain size. Hardly a definitive test, I know. However, that said, thorough blind testing of treated test blades and "regular" blades I found no difference in actual performance in a variety of mediums and techniques when used as a thin knife.

In my opinion, prequenching D2 doesn't hurt anything. But, like full cryo, has not resulted in any noticeable improvements in the finished blade that I can see. I've retained test sample blades if any peer wants to review them.

One needs to be very careful double austenitizing D2 because it is one of the steels that can experience extreme grain growth on a second heat. Something to think about when you consider the thin edges and our electric hot air ovens and the potential for considerable unintended (and unobserved) overshoot in areas.

It has been my observation that the weakness of D2 is fine edge stability. This is caused by its tendency to retain a significant amount of stabilized retained austenite in the majority of the heat treatments it might receive, and it's high carbide fraction. Without going into a great deal of detail (I've beat this horse to death) I'll say that RA, excessive carbide precipitation and carbon lean martensite are not good in knife edges. But are very common and acceptable in most of the applications where D2 is used. Thus, a lot of conventional HT wisdom doesn't always apply well to D2 when used in a knife.

Moderate austenitizing temperatures, relatively rapid quench towards Mf (-100f) without delay and moderate tempering temperature appear to me to work best to maximize this steel's potential. And, when treated this way I have seen it, time and again, beat modern "super steels" in realistic testing. Add to that it is relatively stainless, and the way that the non CPM version cuts flesh and I believe it is one of the best steels available for disassembling chickens and opening up deer etc. Works well around the shop and on cardboard too. Don't underestimate this steel based upon poor examples you may have seen.
 
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