Predicting Toughness with Steel Composition

Once we get into heat treating there are many factors that can affect toughness, mostly when it comes to making it worse instead of better. The extremely detrimental result of overaustenitizing was reported in our CruforgeV toughness testing thread. Tempering too high can lead to a reduction in toughness due to tempered martensite embrittlement, which can be seen in many datasheets. Grain refinement is usually the only way to increase both hardness and toughness.
 
This is great larrin. How could we find the carbide volume of other steels? I'm interested to see how AEBL compares.
Isn't 15n20 the same as l6?
 
valknut said:
Wow I didn't know that. What is it that makes it that tough? Now is it that tough at the commonly used 62rc? Or is it at the 59 like done in this test?
Click to expand...
Because of its much lower carbide volume and carbide size. It is likely tougher across a range of hardnesses but comparing toughness of Steel X at 62 Rc vs Steel Y at 59 Rc is difficult to guess without experimentation.
 
Larrin, when you add the moly to L6 like the Crucible Champalloy, it seems to jack the hardening curve so if you temper at 400F, you end up at 61 instead of 58 or so like with that Latrobe blend, which appears to be what Aldo had. 500
F appears to get you that 57-58 range with the moly bearing stuff. What I see form the provided charts is that the moly stuff drops maybe 15 or no more than 20% in toughness when you go to 61Rc, but the non-moly stuff, seems to drop by like 1/3. Of course, I don't know when to trust these generic charts even ones provided by the mills and messy with that moly L6 sounds like a real chose because of its deeper hardenability.
Larrin said:
CruforgeV toughness: https://www.bladeforums.com/threads/cru-forge-v-toughness-testing.1503654/page-4#post-17295700

Drop in toughness of L6 with tempering above 400F: https://www.alphaknifesupply.com/Pictures/Info/Steel/L6-DS-Latrobe.pdf
Click to expand...
 
I have heard that 12C27 is even tougher but lacking the absolute fine edge stability and the ability to reach higher hardness levels of AEB-L/13C26. Funny how such a tiny bit of alloying element can make a substantial difference.
Larrin said:
AEB-L is much tougher than the commonly used PM stainless steels.
Click to expand...
 
jdm61 said:
Larrin, when you add the moly to L6 like the Crucible Champalloy, it jacks the hardening cube so if you temper at 400F, you end up at 61 instead of 58 or so like with that Latrobe blend, which appears to be what Aldo had. What I see form the provided charts is that the moly stuff drops maybe 15 or no more than 20% in toughness when you go to 61Rc, but the non-moly stuff, seems to drop by like 1/3. Of course, I don't know when to trust these generic charts even ones provided by the mills.
Click to expand...
I’m not sure a Mo addition would provide 3 Rc more in hardness unless the lower Mo Steel isn’t being sufficiently hardened. The higher carbon listed in the Crucible version might do it though. I’m not sure what you’re referring to with the 20% drop vs 33% drop. Drop in toughness by using 61 Rc instead of 58?
 
jdm61 said:
I have heard that 12C27 is even tougher but lacking the absolute fine edge stability and the ability to reach higher hardness levels of AEB-L/13C26. Funny how such a tiny bit of alloying element can make a substantial difference.
Click to expand...
The two are very similar. 12C27 doesn’t get quite as hard but has a little better corrosion resistance and slightly better toughness.
 
Larrin, the first time that I ever saw the thing about the moly altering the hardening mentioned was on Kevin Cashen's website. As for the drop, I am going by the charts that I have seen. One chart that I saw said that the was from like 93 NM to 60 NM. But the same chart who'd 3V at like 58 at 110 NM and at 60 down only a couple of points higher than A2 at 60Rc.
Larrin said:
I’m not sure a Mo addition would provide 3 Rc more in hardness unless the lower Mo Steel isn’t being sufficiently hardened. The higher carbon listed in the Crucible version might do it though. I’m not sure what you’re referring to with the 20% drop vs 33% drop. Drop in toughness by using 61 Rc instead of 58?
Click to expand...
 
Ah. I had never recalled seeing anything that said that there was an appreciable difference in as quenched hardness other than a point or so from moderate differences in austenizing temperature, so that explains it.
DevinT said:
Moly provides tempering resistance.

Hoss
Click to expand...
 
Lapedog said:
I have heard that it is often oversimplified that more hard = less toughness and vice versa.

I heard it is not that simple and there are things you can do to a steel that will make it tougher and harder. For example if you botch the heat treat it can make the steel both softer and less tough.
Click to expand...


My post was meant in a very general way. I’m no metallurgist by any measure.
 
jdm61 said:
Larrin, the first time that I ever saw the thing about the moly altering the hardening mentioned was on Kevin Cashen's website. As for the drop, I am going by the charts that I have seen. One chart that I saw said that the was from like 93 NM to 60 NM. But the same chart who'd 3V at like 58 at 110 NM and at 60 down only a couple of points higher than A2 at 60Rc.
Click to expand...
Every Steel will behave a little differently. They may have had to slightly under-temper or over-austenitize the 3V to get 62 Rc leading to a greater drop in toughness.
 
We have also heard recently about the difference folks have seen in the behavior of 3V using the lower tempering temperatures and the lower austenizing temps for 52100. I seem to recall Kevin talking about how you can "play" with some alloys a little bit, but how with others, you pretty much have to "take what the chemistry gives you." i think he referred to A2 as one of the latter.
Larrin said:
Every Steel will behave a little differently. They may have had to slightly under-temper or over-austenitize the 3V to get 62 Rc leading to a greater drop in toughness.
Click to expand...
 
jdm61 said:
We have also heard recently about the difference folks have seen in the behavior of 3V using the lower tempering temperatures and the lower austenizing temps for 52100. I seem to recall Kevin talking about how you can "play" with some alloys a little bit, but how with others, you pretty much have to "take what the chemistry gives you." i think he referred to A2 as one of the latter.
Click to expand...
I’m not sure I agree with that sentiment but maybe it makes more sense in context.
 
Which sentiment? We have seen the experimenting with both 3V and 52100 of late. Same with AEB-L.
Larrin said:
I’m not sure I agree with that sentiment but maybe it makes more sense in context.
Click to expand...
 
You must log in or register to reply here.
Back
Top