D2 Experts

Big Smitty

Big Smitty

Joined
Aug 30, 2007
Messages
509
I am getting ready to make some knives out of D2. I am going to outsource the HT until I sort out my HT oven situation. I am a D2 virgin and am concerned with the grindability of the steel prior to HT. Does it grind readily? Does it come annealed? Do I have to anneal it? Does it work harden while grinding? Any input is appreciated and will ease my D2 anxiety. Thanks!
 
I have made 50 +/- slipjoint knives from D2. I bring blades to 1880, hold 20 minutes and plate quench. I temper the blades twice @ 500, springs once @ 1200. Works well. I grind after heat treat. Not a problem for small blades. I would not want to grind a large bowie after HT!
 
John L
Would you attempt to grind a 4" blade after HT in 1/8" D2? What grit belts do you use? How about hand polishing D2 after heat treat?
 
D2 prior to HT is not that hard to grind. As John pointed out, after HT it's a bear to grind. D2 is very wear resistant. A 4" blade shouldn't give you much of a problem grinding after HT. I finished mine with a 120 grit 3M Gator and a coarse then fine scotchbrite belts.
Scott
 
I don't think a 4" blade after HT would be a problem at all as most of my slipjoints are 4" or so and most are 1/8" and a few 3/32". I hog with a 36 grit, then 80, 180, 400 and then to a very fine 3M(scotchbrite). I do not mirror or hand sand. My folders are users.
 
D2 has the lowest machinability rating of any steel I commonly work with. 35% of W1. Feh. It comes spheroid annealed, but it is still hard on cutters. I do all my grinding before HT. That is the beauty of an air quench steel, little danger of warping. Protect the blade from oxygen and all you have to do is remove a little heat coloring. I used to use argon, but now I use foil. After HT, I just tumble and use a sctochbrite belt.

I heat treated some last weekend where I ground one down to under a .010 edge. It was .025" almost 1/4" back from the edge. Fortunately no problems. YMMV. I did pull it out of the plates at about 8 seconds and nudged the tip over a hair. It only takes the smallest little nudge with your thumb while still hot.

D2 is designed to retain austenite after quench to minimize warping and dimensional changes (it is a die steel). For maximum performance on a small thin blade you may want to convert some of that retained austenite to martensite with a deep freeze (liquid nitrogen or dry ice and acetone). You will reduce risk of cracking (has never ever happened to me in D2) and warping (happens) with a snap temper at 300 for 20 min before your freeze. In my experience this may reduce the effectiveness of your cold treatment and cost you an RC point, but that may be a good trade off for you. I plan to go back to no snap temper.

My "formula" is preheat at 1400 for half a beer, run up to 1850 and soak at temp for 40 min. Yes, 30 minutes almost certainly works, but there will be no increase in grain size over 10 min in this steel and some of those carbides are pretty large, best to give them a chance to melt as much as they're gonna. I plate quench in the foil. I pull them out and look for kinks before they "set up". They cool off, then go into water, then into dry ice and acetone for 2 hours. I then temper twice for two hours at 450 for a target hardness of around 61-62.

The rapid quench (compared to air), in theory, gives you a point in RC hardness, and may help keep some of the chrome free for better corrosion resistance. This is based upon what I've read. They say that the rapid quench keeps more carbon in the martensite. During temper the carbon comes out of the martensite and forms fine secondary carbides with whatever is close by, including iron, not just the chromium. Might leave more free chromium. I don't know.

Keep in mind, if grinding after HT, that D2 does not run colors at the regular temps. You can botch your temper and never know it...
 
I grind without gloves and don't think the HT is affected by post HT grinding. Perhaps I should soak a little longer. I do plate quench in the foil between two pcs of 6/4" aluminum. Have not had a crooked blade yet. :thumbup:
 
more alloy more time or temp to get every thing moving :)

if your going to grind after heat treat may i tell you to grind a 45 degree at the edge before hardening. you might be suprized at how fast you can take the grit off a belt if you leave the 90s on the blade blank edge

all my air quench steels get ground 80% or better (99% on some like cpmS125v and cpm10v)
 
I ground mine to shape and a 220 grit finish before HT. I am going to go to 400 on the next ones before HT. Before HT it is fairly easy to grind. After much more difficult and uses up belts at a faster rate. I love D2, It is some great steel. I found a some that was old stock from a commercial enterprise and now have 10 pieces 12.5" x39.5" .211 thick. So I figure to know a lot more about D2 as I use it up. LOL
 
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