oil quenching d2 to reduce austintite and refine grain

[me2]

It has been my observation that the weakness of D2 is fine edge stability.

Can you elaborate on this a little? Do you mean fine as in high polish, or fine as in low edge angle (10 degrees per side or less), or both?

 

[james terrio]

me2, I would not presume to speak for Nathan, but in my experience* D2 has a remarkable tendency to chip when ground to a thin, acute edge.

*I have several thousand hours' experience with paper-cutting dies and slitters made of D2. It's chippy in that application. I also have a few dozen hours experience with a pocket-knife made of D2; it's chippy in that application also.

 

[me2]

Do you use very low edge angles on your knife, like less than 10 degrees per side? What kinds of geometries are used on the dies and slitters? How does D2 fair on knives like the Outcast, if you've tried it? I'm just trying to put a number on it, as my fine acute edge and yours might be pretty far apart.

 

[james terrio]

I've never examined a Kershaw Outcast. My Queen Mountain Man folder is sharpened somewhere in the neighborhood of 15 degrees inclusive and slices aggressively but not super-cleanly.

The tools I used all those years in the pressroom were ground more like 20 degrees inclusive (I'm estimating from memory), quite hard, and quite fragile; as in, a grain of dirt would cause a small chip. None of them were "shaving sharp".

You have to keep in mind, rotary paper-cutting dies and slitters do not "cut" in the same way we would shave hair off our arm or slice a ribbon off the edge of a sheet of typing paper with a hand-held knife; they work under relatively low pressure on substrates under tension, that are running over a hard "anvil" roller. They crush material and force it apart, rather than slicing it. If the edge of the tool has more than the barest contact with the anvil (we called it "kissing") it will chip and/or be deformed, resulting in a rough "cut", poor quality, and much gnashing of teeth and harsh words.

I daresay that I have cut far more paper, film, Tyvek and cardboard than any man on this forum, but in a totally different way. It's apples and oranges, or perhaps razors and splitting mauls.

I'm drifting far off topic now, but... I'm always stunned when folks describe D2 as a "tough" steel. The reason D2 is used so widely in industry has almost nothing to do with sharpness or impact toughness; its greatest attribute is wear-resistance.

 

[hammerfall]

hi nathan. the extrame grain growth usually occure on the 4th or fifth austenitizing for me lol. it never appeared on the second unless over heated it to a big degree. i think the second quench is safe to do since the grain is not yet small enough to become unstable with original grain boundary. anyway, you are more experienced with D2 i guess.

btw i might be little bit confusing and missleading in my last post. i did not mean to recommand using lead bath or induction heating to treat d2. acctrully induction heating somehow has a very big potential causing the EXTRAM grain growth on multi austenitizing. worst thing is this type of fast heating cannot really control the temperature from meter, it depends on time experience more than anything. get rid of RA, keep the second austenizing temperature lower than the first helps decrease the chance of inheirtage or extram grain growth as well.

 

[lazlo]

I've never examined a Kershaw Outcast.

I have one. You wouldn't think a big chopper should be made from D2, but I've beat the hell out of it, and it hasn't chipped. The various heat treat guides indicate lower austentizing temperature and higher tempering temperature to maximize D2's toughness at the cost of some wear resistance. I gather that's what Kershaw/Ken Onion has done.

 

[Nathan the Machinist]

Can you elaborate on this a little? Do you mean fine as in high polish, or fine as in low edge angle (10 degrees per side or less), or both?

The industry standard HT for D2 encourages lots stabilized RA. This is intentional because it reduces dimensional changes due to HT in the tooling made from it. It might also improve impact performance in thick sections. This is great in a stamping or forming tool, but not so great in a knife edge.

The problem is, these areas of RA and the large carbides act almost like the perforations in a book of postage stamps when they're found in thin sections like a narrow knife edge. Thus the problem with edge stability and the reputation for being chippy (and suffering edge roll even at high hardness). D2 with good fine edge performance requires thoughtful heat treat, though it isn't rocket science.

The RA is easily avoided, and the literature referenced by the OP actually goes into it really well. And the low tempering temp maximizes the strength of the martensite while minimizing secondary carbide precipitation, which maximizes fine edge stability and also maximizes free chromium to the point it is nearly stainless. Treated properly for our use, D2 is tougher and more durable than any other stain resistant wear resistant steel I've tested. And I've seen no other steel that cuts flesh quite like it, making it a really cool alloy for certain kinds of knives, which is why some of use continue to use it despite the development of more modern alloys.

 

[clockworkfish]

The industry standard HT for D2 encourages lots stabilized RA. This is intentional because it reduces dimensional changes due to HT in the tooling made from it. It might also improve impact performance in thick sections. This is great in a stamping or forming tool, but not so great in a knife edge.

The problem is, these areas of RA and the large carbides act almost like the perforations in a book of postage stamps when they're found in thin sections like a narrow knife edge. Thus the problem with edge stability and the reputation for being chippy (and suffering edge roll even at high hardness). D2 with good fine edge performance requires thoughtful heat treat, though it isn't rocket science.

The RA is easily avoided, and the literature referenced by the OP actually goes into it really well. And the low tempering temp maximizes the strength of the martensite while minimizing secondary carbide precipitation, which maximizes fine edge stability and also maximizes free chromium to the point it is nearly stainless. Treated properly for our use, D2 is tougher and more durable than any other stain resistant wear resistant steel I've tested. And I've seen no other steel that cuts flesh quite like it, making it a really cool alloy for certain kinds of knives, which is why some of use continue to use it despite the development of more modern alloys.

So it is better to have as little RA as possible right? Also is there an advantage to the higher tempering temp? i feel like i have heard it does something in addition to putting the rc at around 60. Lastly would it be smart to use an oil quench or even a double oil quench?

Thanks for your input on d2 Nathan!

 

[SteelSlaver]

I have had excellent results with D2 in medium and small hunting knives. No problem dressing multiple deer and still shaving hair. Very wear resistant.

Current HT is holding at 1850f for 45 min. Long enough for the steel to get up to 1850 and then soak for 30 min +. Then plate quench and into a solution of dry ice and kerosene for about an hour. Then 2 hours at 400f then back in the dry ice/kerosene then another 2 hours at 425f. I added the second dry ice/kerosene soak on the last batch and have not formed a solid opinion of added performance yet. Everyone I sold locally got great reviews after last hunting season.
Done like this it will hold an edge that will shave hair (but I wouldn't shave with it)

I finish to at least 400 pre HT and then hit it with more 400 then 600 and 1200. Use lots of fresh paper as it will dull the paper fast. At 1200 and some buffing you can see patterns in the steel.

You can't do parlor tricks with D2 and beat on the spine with a hammer or flex it much. But, you can depend on it to keep cutting well.

Also like many steels D2 has a fair range for some of its alloys and whick D2 may be part of the reason some have not had the results of others.

 

[Matthew Gregory]

The industry standard HT for D2 encourages lots stabilized RA. This is intentional because it reduces dimensional changes due to HT in the tooling made from it. It might also improve impact performance in thick sections. This is great in a stamping or forming tool, but not so great in a knife edge.

The problem is, these areas of RA and the large carbides act almost like the perforations in a book of postage stamps when they're found in thin sections like a narrow knife edge. Thus the problem with edge stability and the reputation for being chippy (and suffering edge roll even at high hardness). D2 with good fine edge performance requires thoughtful heat treat, though it isn't rocket science.

The RA is easily avoided, and the literature referenced by the OP actually goes into it really well. And the low tempering temp maximizes the strength of the martensite while minimizing secondary carbide precipitation, which maximizes fine edge stability and also maximizes free chromium to the point it is nearly stainless. Treated properly for our use, D2 is tougher and more durable than any other stain resistant wear resistant steel I've tested. And I've seen no other steel that cuts flesh quite like it, making it a really cool alloy for certain kinds of knives, which is why some of use continue to use it despite the development of more modern alloys.

What Nathan said.