D-2 or A-2 Opinions please?

A

Agent Iron

Joined
Feb 5, 2005
Messages
299
First off, what a great site!

I have been craving to make a knife, and with all the wonderful options available, it makes it both exciting and perplexing. My brother in law is a tool and die maker, and he has some neat tools at his disposal will do most of the work on the project. I had it in my mind that A-2 would likely be the best steel for a durable all purpose survival chore type of blade. I mentioned to him that from what I have read it looked like A-2 would be the better choice over D-2 and he was kind of dumbfounded. He has a few years of mettleurgy and makes tools for a living using primarily A-2 and D-2, and he says....no way will A-2 be more durable, not even close.

Is there something he is missing here, could you fellas provide some insight on which is superior and why, I would really appreciate it.

AI
 
I like A2 because I know it. I haven't made friends with D2 yet, but would like to someday :D. From what I know, D2 is more wear resistant than A2, but, to me at least, D2 is really "picky" (for lack of a better word.) to work with. Something to do with large carbides. Anyways, D2 is more tricky than A2.
I'm sure that the metallurgists will chime in and explain it better than me.;)
- Mitch
 
I'm no metallurgist, but I slept on a bus last night. I think A-2 will be tougher whereas D-2 will be more wear and stain resistant. I'll bet A-2 is easier to sharpen, although I own no A-2 or D-2 blades.
 
I may be an ignorant kid, but A2 is tougher that D2! D2 has higher tensile strength (i think), but A2 has better toughness. You may want to start on a cheaper, simpler steel like 1080 or 5160, because you can heat treat them yourself and they are pretty good.

A2 also rusts faster than D2, but with a little oil that shouldn't be a problem.
 
Maquahuitl said:
I'm no metallurgist, but I slept on a bus last night. I think A-2 will be tougher whereas D-2 will be more wear and stain resistant. I'll bet A-2 is easier to sharpen, although I own no A-2 or D-2 blades.
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Generally speaking, yes...A2 is a little tougher than D2. But, it all depends on the HT. If you get somebody who really knows D2, it can be a really tough, wonderful steel.
- Mitch
 
This is great fellas, keep it coming.

My brother in law is very familiar with the heat treating process of both steels, and uses them often in making part and dies for a manufactureing plant. How would we distinguish toughness compared to durability? I thought maybe the D-2 would be more brittle, but he insists that it is not. He says he can make dies for people that after years of use will look perfect when made from D-2, where the A-2 may need some work. The encourage businesses to go with D-2 if they want no maintenance, and A-2 if they want to save money and have them touch up what is neccesary in the future.

Now I am not sure how A-2 and D-2 compare if prying, or are being torqued, maybe the D-2 is more brittle.

Any other ideas would be outstanding.
AI
 
Agent Iron said:
This is great fellas, keep it coming.

My brother in law is very familiar with the heat treating process of both steels, and uses them often in making part and dies for a manufactureing plant. How would we distinguish toughness compared to durability? I thought maybe the D-2 would be more brittle, but he insists that it is not. He says he can make dies for people that after years of use will look perfect when made from D-2, where the A-2 may need some work. The encourage businesses to go with D-2 if they want no maintenance, and A-2 if they want to save money and have them touch up what is neccesary in the future.

Now I am not sure how A-2 and D-2 compare if prying, or are being torqued, maybe the D-2 is more brittle.

Any other ideas would be outstanding.
AI
Click to expand...

Don't say that "D2 is brittle" to Sam Salvati!:D:eek:
(Inside Joke) Right, Sam?
- Mitch
 
Agent Iron said:
Now I am not sure how A-2 and D-2 compare if prying, or are being torqued, maybe the D-2 is more brittle.


AI
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With my limited expirence w/ both steels I think that this may be where your bro-in-law the tool and die maker and you, the knife user, seperate. D2 is fairly brittle when torqued which doesnt happen much in the press world where it is primarily used. YMMV
 
D-2 being semi stainless (Cr: 12.0 vs 5.0 for A2)

My Machinerys handbook gives a scale from A-E (A= greatest, E= Least) for these characteristics:
Wear resistance:
A2- D
D2- E
Machinability
A2- D
D2- E
Toughness:
A2- D
D2- E
Grindability:
A2- A
D2- B

Both have an "A" for safety of hardening and are air quench.

hope that helps...
 
In the end, it's all about how well it's heat treated. Get a goober to heat treat either one, and both will be inferior to your common kitchen knife bought at walmart :D
 
I love D2, but a few years ago, when I decided to make a knife for my teen aged grandson, I suggested A2. Why? After discussing the issues with him, he understood that he would have to keep it dry and oiled because A2 would rust much quicker than D2.

My feeling was that with A2 I could grind the edge a little more acute and not worry about him chipping it. A2 is much more resistant to damage while using the knife to chop limbs and such. I didn't think that it would hold an edge as well as D2, however it has been a very good edge holder. It is good at edge holding probably because of the toughness.

I had it heat treated by Paul Bos to HRC 60 ( the sweet spot for A2 as a knife ), and it has been a great performer for him. He loves that knife!
 
I found some good stuff at the site below. The site indicates that D2 is more wear resistant then A2, which appears contrary to what Shadetree found in his book. It seems contrary to what my brother in law experiences. If what Shadetree quoted is true, it would seem that A2 would be the hands down winner as it excells in all catagories.

http://www.cutleryscience.com/reviews/blade_materials.html#T_A2

A2 is an air hardening cold work die steel. The significant amounts of chromium and molybdenum makes it more dimensionally stable than O1. They also require much higher austenization temperatures to dissolve than the water/oil hardening steels and thus A2 is typically austenized at 1750/1800 F. The heating is usually done in stages to minimize thermal gradients in the steel and reduce the hold time at the austenization temperature to prevent grain growth.

The dissolved alloy elements and high carbon content will cause significant percentage of retained austensite if the quench is halted at room temperature and result in a loss of 2.5-3 HRC points. With oil + cold A2 can can harden up to 64/65 HRC and will resist significant softening up to 1000 F (57/59 HRC). A2 has moderate wear resistance (A2 is 6, O1 is a 4 and D2 is an 8 : ref) and good impact toughness. The grain fracture size with standard industy heat treatment is 8.5. Some specification and performance data sheets on A2 from various manufacturers :
 
That's a poor source to quote !! Both A-2 and D-2 are used by many knife makers and both do very well at that job.The Major difference in my opinion is that D-2 is stainless. Both REQUIRE precision HT to get the best properties so unless you have the proper equipment and knowledge leave the HT to an expert ! Comapirive data can be found on www.crucibleservice.com
 
I'll point out that mete is a metallurgist.

I'll point out that I really really like D2 for a knife, but only thin small precision cutters, not large knives you might chop with or knives needing thick edges. A2 would be better there.

There are three basic ways an edge goes dull. Rolling, chipping or abrasive wear. Edge rolling is more a function of geometry and heat treat than alloy. A2 is probably a little better than D2 in edge chipping, D2 is better than A2 in abrasive wear and has good rust resistance too. Does your application need abrasive wear or edge stability?

I was a machinist and did some tool and die work and thought I knew a lot about A2 and D2 and heat treat, but found I was wrong. I'll save you some learning steps:

These steels shine at higher harnesses, choose something else for softer blades
These steels need to soak at temp for half an hour regardless of thickness; do not apply the half hour per inch "rule", is is wrong for knifes.
This time at these temps robs the steel of carbon if exposed to air (makes CO2); use foil wrap or argon.
Read up on plate quenching.
Stay away from secondary hardening nose (IMHO), temper below 600 (I do D2 at 515 or lower, I do dies etc around 900)
These steels are designed to retain austenite for dimensional stability in tool and die; not your application, read up on cryo.


Hey troop, don't say D2 isn't brittle to Cliff Stamp, his hissy fit might get him banned....
 
I don't think most of these people actually read your first post where you described this as a survival-type knife. For a survival knife you are looking for toughness (resistance to breaking) and A2 is much tougher than D2. This assumes that you are going to be chopping with your blade through tough knotty wood and maybe bone. Now if you are just speaking figuratively about a "survival-type" knife and you are just going to use it as a hunting knife D2 is much more wear resistant and will hold an edge longer.

If you really plan to be rough on the knife and pound it with rocks while trying to split logs even A2 is likely not tough enough. In that case you might want 1084 or 5160 carbon steel that is differentially heat treated so that the blade edge is harder than the spine.

As a side note, A2 has less carbides and smaller carbides which lets it take a finer edge and makes it tougher. D2 has more carbides and larger carbides which make it resist wear, but it takes a rougher edge and holds it long time.

Your brother may be used to using these alloys at lower hardness than you want for a knife. Most people do A2 at 60 RC and D2 a little harder. That might affect his view of how durable they are. I would say that "durable" in his sense is how long they hold an edge in a stamping press, this is more wear resistance than toughness.
 
I like A2. It is easier to handl it for the user. It is very tough and more or less stainless. I know about ATS, D2 and stuff, but I stick to A2.
For brutal duties I would use 52100 or 5160. Less hardness and"softer" edge, but hard to break the blade if HT-ed properely.
 
Agent Iron said:
I found some good stuff at the site below. The site indicates that D2 is more wear resistant then A2, which appears contrary to what Shadetree found in his book. It seems contrary to what my brother in law experiences. If what Shadetree quoted is true, it would seem that A2 would be the hands down winner as it excells in all catagories.
:
Click to expand...

Not really, IMO. There are pretty close. If the scale goes from A-E, then the two might be very close in say Wear resistance: A2- D, D2- E In this case on a relative scale A2 is in the 21-40% range, with D2 in the 1-20% range, so they could be very close (say 15% vs 25%). I think the handbook says that A2 edges out D2, but not as significantly as you you suggest. IMO, being semi stainless, D2 wins. There is a reason they are popular for knives, They can both work very well.

Of course, I am no expert and this is taken out of the Handbook losing context to some extent
 
I have been using both steels for years. For a long time I went with the party line: A2=tougher, D2=better wear resistance.

After a lot of experience with both, I have concluded that the differences in wear resistance are not really as noticable in use as knives as it may be in machine tool use. I haven't had any problems with breaking D2. I harden both to RC60.

As noted, D2 is far more rust resistant, but here in the SW, A2 is noticably better than the Carbon steels like O1 and the 10XXs.

I have had knives I made from both steels used to process multiple animals without sharpening.
 
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