Ranking Toughness of Forging Knife Steels

Fallbrook Forge said:
What have you broken 80CRV2 blades doing?
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Side by side testing with other steels. In my break tests 80crv2 is not impressively tough compared to others. One really big company is using it as a replacement for 4140!!! One of the toughest steels you can use for a cutting tool. I’m not saying it’s bad steel. It’s a pretty decent steel. But it’s being promoted as a replacement for 5160. I guess further testing will reveal the truth. In the meantime, if I want a cheap super tough steel, I’ll continue using 8670!
 
rodriguez7 said:
Toughness. Some companies are using it in place of 4140, seriously!! 8670 smokes it in toughness and edge retention doesn’t seem to be much less. 52100, and all these other high alloy tool steels seem better. It’s an ok steel, and the price is good. But there are better options. It just got a lot of hype for some reason.
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100% agree!
rodriguez7 said:
Side by side testing with other steels. In my break tests 80crv2 is not impressively tough compared to others. One really big company is using it as a replacement for 4140!!! One of the toughest steels you can use for a cutting tool. I’m not saying it’s bad steel. It’s a pretty decent steel. But it’s being promoted as a replacement for 5160. I guess further testing will reveal the truth. In the meantime, if I want a cheap super tough steel, I’ll continue using 8670!
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I 100% agree with you. 80crv2 is probably an ok Steel for everything, just adjusting the edge geometry and it can have good edge retention or good toughness. But, come on! Using it in a breaching/unbreakable tool to replace 4140??? To replace 4140, I would go with 4340, 300M or Aermet type of stuff, not an 0,80% carbon steel... I’m sure a big and reputable company can have a big sheet of these materials rolled in the thickness they want.
 
I love these articles, Larrin, thank you.
However, as we keep claiming the 5160 and 8670 are at the top of the heap, I have to note that there's only one datum for each on the graph. Are there more samples in process? It would be great to see several samples up through 63Rc for each, if they'll get that hard. Also, it would be great if there were some lower hardness tests for the competing steels. Basically we need more overlap in hardness ranges for those two seriously tough materials.
Easy for me to say from my office chair. :rolleyes:
 
daizee said:
I love these articles, Larrin, thank you.
However, as we keep claiming the 5160 and 8670 are at the top of the heap, I have to note that there's only one datum for each on the graph. Are there more samples in process? It would be great to see several samples up through 63Rc for each, if they'll get that hard. Also, it would be great if there were some lower hardness tests for the competing steels. Basically we need more overlap in hardness ranges for those two seriously tough materials.
Easy for me to say from my office chair. :rolleyes:
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Yeah, we could spend a lifetime on every alloy out there, just not time to do them all. I don’t think most members here realize how much time is put into all this testing, especially from Larrin and Warren. We have never had a PhD this interested in knives before, John Verhoeven did a lot for knife makers also.

All of this is very exciting and I encourage everyone to get involved.

Much respect,

Hoss
 
daizee said:
I love these articles, Larrin, thank you.
However, as we keep claiming the 5160 and 8670 are at the top of the heap, I have to note that there's only one datum for each on the graph. Are there more samples in process? It would be great to see several samples up through 63Rc for each, if they'll get that hard. Also, it would be great if there were some lower hardness tests for the competing steels. Basically we need more overlap in hardness ranges for those two seriously tough materials.
Easy for me to say from my office chair. :rolleyes:
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There were two tests done for 8670. More specimens are awaiting machining. A whole range of specimens were done with 5160, only the best is shown on the chart. Anyone who feels more specimens are required to satisfy their curiosity is invited to heat treat the specimens, machine them, and send them to me. https://knifesteelnerds.com/2019/04/01/how-to-heat-treat-5160/
 
daizee said:
I love these articles, Larrin, thank you.
However, as we keep claiming the 5160 and 8670 are at the top of the heap, I have to note that there's only one datum for each on the graph. Are there more samples in process? It would be great to see several samples up through 63Rc for each, if they'll get that hard. Also, it would be great if there were some lower hardness tests for the competing steels. Basically we need more overlap in hardness ranges for those two seriously tough materials.
Easy for me to say from my office chair. :rolleyes:
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8670 at Rc64 is down around the 1095 range iirc. It was tempered at 175f. We have more 8670, 80crv2, and z-tuff awaiting machining.

I almost have my shop set up now, and have recovered from the motor replacement on my car, so a surface grinder is the next piece of equipment after I finish the press.
 
Willie71 said:
8670 at Rc64 is down around the 1095 range iirc. It was tempered at 175f. We have more 8670, 80crv2, and z-tuff awaiting machining.

I almost have my shop set up now, and have recovered from the motor replacement on my car, so a surface grinder is the next piece of equipment after I finish the press.
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Curious what hardness samples you have done for ztuff? Due to some major personal life setbacks, I have not been able to send you any steel with the heat treat suggestions we talked about! But I’m still interested. Thanks.
 
hugofeynman said:
100% agree!


I 100% agree with you. 80crv2 is probably an ok Steel for everything, just adjusting the edge geometry and it can have good edge retention or good toughness. But, come on! Using it in a breaching/unbreakable tool to replace 4140??? To replace 4140, I would go with 4340, 300M or Aermet type of stuff, not an 0,80% carbon steel... I’m sure a big and reputable company can have a big sheet of these materials rolled in the thickness they want.
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My thoughts exactly!
 
rodriguez7 said:
Side by side testing with other steels. In my break tests 80crv2 is not impressively tough compared to others. One really big company is using it as a replacement for 4140!!! One of the toughest steels you can use for a cutting tool. I’m not saying it’s bad steel. It’s a pretty decent steel. But it’s being promoted as a replacement for 5160. I guess further testing will reveal the truth. In the meantime, if I want a cheap super tough steel, I’ll continue using 8670!
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We started workshop groups through my mental health company. I am starting everyone off with reclaimed 15n20, then 8670. Super easy to work with. Easy to heat treat, and it would even work well heat treated in a forge.
 
rodriguez7 said:
Side by side testing with other steels. In my break tests 80crv2 is not impressively tough compared to others. One really big company is using it as a replacement for 4140!!! One of the toughest steels you can use for a cutting tool. I’m not saying it’s bad steel. It’s a pretty decent steel. But it’s being promoted as a replacement for 5160. I guess further testing will reveal the truth. In the meantime, if I want a cheap super tough steel, I’ll continue using 8670!
Click to expand...

I wouldn't mind hearing the expanded version of your testing, if you wouldn't mind.
 
daizee said:
I love these articles, Larrin, thank you.
However, as we keep claiming the 5160 and 8670 are at the top of the heap, I have to note that there's only one datum for each on the graph. Are there more samples in process? It would be great to see several samples up through 63Rc for each, if they'll get that hard. Also, it would be great if there were some lower hardness tests for the competing steels. Basically we need more overlap in hardness ranges for those two seriously tough materials.
Easy for me to say from my office chair. :rolleyes:
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Why should you do that ? 5160 is spring steel , right ? 5160 have excellent toughness under 60 HRC .....like on 55-58 hrc .What do you want more from that steel , to make folder and to stay sharp forever ? It is not steel designed to cut forever my friend .............in big heavy used blade that steel will be home .
 
Zeunerite said:
Why not? Why should we assume a steel is no good beyond what it's normally hardened at if we never actually test it?
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Because it is predictable ? Increasing hardness you will lose toughness? Is it worth for two more cuts ?
 
Larrin said:
Summary of toughness measurements on a range of low alloy steels used by forging bladesmiths but also stock removal makers. Then an explanation of what factors control the toughness of low alloy steels. And information on how heat treatment affects the toughness of these steels. https://knifesteelnerds.com/2020/02/17/ranking-toughness-of-forging-knife-steels/
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Larrin Larrin ,where/how would san-mai steel be ranked on the scale of toughness? It can not be tested on that machine because it will not break ? I mean on san-mai with hard core and soft sides....
 
Natlek said:
Larrin Larrin ,where/how would san-mai steel be ranked on the scale of toughness? It can not be tested on that machine because it will not break ? I mean on san-mai with hard core and soft sides....
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The orientation would be somewhat difficult to get right in terms of making something that would reasonably test San-mai. The dimensions don’t translate well between the two. And even if we came up with something reasonable there are a million decisions about what steels and heat treatment we would even test. Of course in terms of edge toughness the laminate doesn’t make a difference.
 
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