A2 steel - History and Properties

cotdt said:
It's not obvious from the composition why 52100 > A2 > O1 in toughness. Maybe it's the quality of the steel itself?
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I’m comparing two supplies of 52100 with slightly different compositions. One with 0.92% carbon, and one with 1.0% carbon. I’m curious about this too.
 
DevinT said:
The old tool steels book shows the same thing.

Hoss
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I must have been misinformed on 52100 being less tough. I found 52100 to be more wear resistant and maybe assumed it was less tough? I also remember preferring 15n20 @ Rc62 to O1 @ Rc60. I only made one O1 knife above Rc62 and gave that knife to my mom for Christmas yeas ago. I have no real world experience with O1 above Rc60.
 
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cotdt said:
It's not obvious from the composition why 52100 > A2 > O1 in toughness. Maybe it's the quality of the steel itself?
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Toughness is very complex, we don’t always have simple answers. It could be that O1 has lower toughness due to more carbon in solution. A2 and 52100 have lower carbon in solution because of the chromium additions. And 52100 has finer carbides so it is tougher than A2. Or there could be other factors.
 
52100 looks like it’s a great mid level steel! I always heard A2 was really tough, but it doesn’t look impressive to me! In the limited testing I’ve done, A2 was not very good. And of course before this, I wasn’t able to get 52100 to the hardness I wanted. One day I want to do a little more testing on 52100. I just never have the time with work, and my 4 year old. But I appreciate everyone’s time and detailed testing. You guys have saved me some valuable time. Keep up the good work.
 
Larrin said:
I usually think of air hardening steels as being easier to heat treat because quenching is less critical. And 5160 and CruForgeV toughness testing we have done shows that low alloy steels are highly sensitive to overheating during austenitizing. I think the reputation of low alloy steels to be "easy" to heat treat is kind of misguided. Easier to harden with a torch or a forge, yes, easier to get a good heat treat no.
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I think “harder to heat treat” = needs more expensive and precise equipment.
 
jdm61 said:
That is very interesting. I would have not expected A2 to be lower on the toughness scale than high hardness CFV as A2 is generally promoted for its inherent toughness at the expense of some abrasion resistance compared to say D2. It looks like it has more of the latter than expected but considerable less of the former.
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I wonder if the CFV vanadium pinning the grain boundaries is part of the toughness.
 
Maybe. CFV appears to be kind of weird. Adam Desroisiers said that it acts funny if you get it below 59Rc or so. It certainly has a good chunk of vanadium.
Willie71 said:
I wonder if the CFV vanadium pinning the grain boundaries is part of the toughness.
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jdm61 said:
Maybe. CFV appears to be kind of weird. Adam Desroisiers said that it acts funny if you get it below 59Rc or so. It certainly has a good chunk of vanadium.
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There is so much to learn. I was sure up until this week that A2 would be tougher than 52100. The fact that z-wear/cru-wear is tougher with double the edge holding is just amazing. I commented to my wife how rather testing has shown most of my observations in real world use to be true. The extent of the difference is amazing.
 
Willie71 said:
There is so much to learn. I was sure up until this week that A2 would be tougher than 52100. The fact that z-wear/cru-wear is tougher with double the edge holding is just amazing. I commented to my wife how rather testing has shown most of my observations in real world use to be true. The extent of the difference is amazing.
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52100 is the beast between non pm steels. It’s a steel that can achieve an ultra fine grain. I think some guys consider AEBL to be the stainless version of 52100, correct? On theory, it can even be much tougher with bainitic heat treatment, and hardness will be good (58-60hrc). Someone with some molten salt pots should try to harden some coupons to lower bainite.
 
Is perhaps the reputation of A2 being very tough that it can have good results from a broad range of heat treatment?
 
Willie71 said:
I’m comparing two supplies of 52100 with slightly different compositions. One with 0.92% carbon, and one with 1.0% carbon. I’m curious about this too.
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I would like to see comparison between that two 52100 steel and say with steel used in NSK ball bearing or with one of SKF explorer series bearing . ....
 
Thanks for another great article, Larrin.
I'm surprised that A2 isn't showing higher toughness - I figured it would beat out CPM154. In my experience, it takes a fantastic edge, and doesn't dull with the same characteristics as stainless steels I use, but I don't really have good vocabulary for or a way to quantify that.

Is there some 154CM in the testing pipeline? I think that's a good one to peg the improvement of the CPM process over standard.
 
daizee said:
Thanks for another great article, Larrin.
I'm surprised that A2 isn't showing higher toughness - I figured it would beat out CPM154. In my experience, it takes a fantastic edge, and doesn't dull with the same characteristics as stainless steels I use, but I don't really have good vocabulary for or a way to quantify that.

Is there some 154CM in the testing pipeline? I think that's a good one to peg the improvement of the CPM process over standard.
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Just because there are steels that are tougher doesn’t mean A2 is “bad.”

I don’t think any 154CM is on deck. I would also like some more CPM-154 tests to confirm the initial result and to see different hardnesses.
 
Larrin said:
Just because there are steels that are tougher doesn’t mean A2 is “bad.”

I don’t think any 154CM is on deck. I would also like some more CPM-154 tests to confirm the initial result and to see different hardnesses.
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No CPM-154 on my lists of what has been promised.
 
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