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What is tougher?
Posted: Mon Feb 04, 2019 5:31 pm
by ZMW
K390 vs Rex-45?
Do we know the difference yet? And, are we just splitting hairs at this point. Their composition is different but they seem to be a good choice for a tougher high edge retention steel. Thoughts?
Re: What is tougher?
Posted: Mon Feb 04, 2019 5:33 pm
by Pelagic
I've heard so many great things about k390, and the cobalt in Rex45 makes me want to lean towards k390. Should be somewhat close. K390 DOES have more carbon. Probably depends on HT and carbide formation specifics (aside from hardness).
Re: What is tougher?
Posted: Mon Feb 04, 2019 5:52 pm
by ZMW
What is the mechanism to measure toughness, do they put a slab of steel in a vice and bend it? Is it scientific, or just user experience?
Re: What is tougher?
Posted: Mon Feb 04, 2019 5:59 pm
by bearfacedkiller
It will depend on heat treat probably. K390 has way more carbon content but REX45 in Spyderco knives is supposed to be run quite hard.
Charpy testing is the scientific way it is tested. Informal testing and anecdotal evidence has value as well.
Re: What is tougher?
Posted: Mon Feb 04, 2019 6:49 pm
by attila
I've also been
very curious about toughness, wear resistance, strength, and corrosion resistance differences between K390 and Rex 45. I've not found solid answers because no head-to-head comparisons have been done.
Here's a visual aid:
FYI, the legend does not obscure the Co parameter. Rex 45 has 8%, just as it looks.
Re: What is tougher?
Posted: Tue Feb 05, 2019 10:50 am
by Doeswhateveraspidercan
I do not have REX45 experience but K390 rusts extremely fast. I used my Police4 in the kitchen washed the blade with soap and water and used a wash cloth to wipe it off.... Walked away left it on the counter blade out and came back a short time later found orange rust dots all over it, rushed it to the bench and broke out the flitz.
It cleaned up nicely but can not recommend this steel if corrosion is a deal breaker.
Re: What is tougher?
Posted: Tue Feb 05, 2019 11:24 am
by PStone
Doeswhateveraspidercan wrote: ↑Tue Feb 05, 2019 10:50 am
I do not have REX45 experience but K390 rusts extremely fast. I used my Police4 in the kitchen washed the blade with soap and water and used a wash cloth to wipe it off.... Walked away left it on the counter blade out and came back a short time later found orange rust dots all over it, rushed it to the bench and broke out the flitz.
It cleaned up nicely but can not recommend this steel if corrosion is a deal breaker.
That happens to me frequently too. Our municipal water system uses a lot of chlorine in our water. I think that’s what’s going on in my case. I don’t know all the chemicals in my cities water, but chlorine is for sure.
Re: What is tougher?
Posted: Tue Feb 05, 2019 11:55 am
by Doeswhateveraspidercan
oh so it is chlorine that does that? I live in Florida = super heavy chlorine, have to filter water just to cook or drink.
Re: What is tougher?
Posted: Tue Feb 05, 2019 12:52 pm
by PStone
Yep. Most likely culprit. Even some brands of bottled water contain chlorine. Try a bottle of “natural spring water” next time on that amazing k390, and I bet you’ll notice a difference if left out in the same manner.
Re: What is tougher?
Posted: Tue Feb 05, 2019 8:02 pm
by jpm2
With my use, rex45 suffers less edge damage than k390. Whether that translates to tougher, I don't know.
I never oil my blades and they cut corrosive materials all the time. They just get rinsed with whatever water is available, and wiped dry. They never rust. This includes 1095 and 52100, which are two of the least corrosion resistant knife steels there are.
Re: What is tougher?
Posted: Tue Feb 05, 2019 8:26 pm
by vivi
Doeswhateveraspidercan wrote: ↑Tue Feb 05, 2019 10:50 am
I do not have REX45 experience but K390 rusts extremely fast. I used my Police4 in the kitchen washed the blade with soap and water and used a wash cloth to wipe it off.... Walked away left it on the counter blade out and came back a short time later found orange rust dots all over it, rushed it to the bench and broke out the flitz.
It cleaned up nicely but can not recommend this steel if corrosion is a deal breaker.
FWIW I've had the opposite experience. Cutting food and washing it off with nothing but hot water I haven't seen any orange rust at all, and barely any patina. K390 is in another league of rust resistance compared to stuff like 1095 and O1 for me when it comes to food prep at camp and in the kitchen.
My sweat gives it orange rust spots within an hour though. Spring is gonna be interesting considering 65-70 degree afternoons are enough to get the rust going.
Re: What is tougher?
Posted: Tue Feb 05, 2019 11:57 pm
by JacksonKnives
ZMW wrote: ↑Mon Feb 04, 2019 5:52 pm
What is the mechanism to measure toughness, do they put a slab of steel in a vice and bend it? Is it scientific, or just user experience?
Charpy tests are close to that. They use a pendulum to measure how much force is absorbed before fracture. V-notch specimines break a little differently than unnotched or other notch shapes, and it's not a directly comparable test to anything other than prybar use, but it's a good number to know.
Steel mills often release data sheets with charpy test results, but sometimes they're hard to find.
Larrin at knifesteelnerds.com has some great posts about toughness and edge stability, check out his site for sure. He just tested some new samples at different hardnesses and he's building a table so we can see how hardness and toughness relate in different steel structures.
Re: What is tougher?
Posted: Wed Feb 06, 2019 7:09 am
by Doeswhateveraspidercan
Vivi wrote: ↑Tue Feb 05, 2019 8:26 pm
Doeswhateveraspidercan wrote: ↑Tue Feb 05, 2019 10:50 am
I do not have REX45 experience but K390 rusts extremely fast. I used my Police4 in the kitchen washed the blade with soap and water and used a wash cloth to wipe it off.... Walked away left it on the counter blade out and came back a short time later found orange rust dots all over it, rushed it to the bench and broke out the flitz.
It cleaned up nicely but can not recommend this steel if corrosion is a deal breaker.
FWIW I've had the opposite experience. Cutting food and washing it off with nothing but hot water I haven't seen any orange rust at all, and barely any patina. K390 is in another league of rust resistance compared to stuff like 1095 and O1 for me when it comes to food prep at camp and in the kitchen.
My sweat gives it orange rust spots within an hour though. Spring is gonna be interesting considering 65-70 degree afternoons are enough to get the rust going.
65 to 70 degrees spring. Lol that's winter here!
Re: What is tougher?
Posted: Wed Feb 06, 2019 9:16 am
by koenigsegg
jpm2 wrote: ↑Tue Feb 05, 2019 8:02 pm
With my use, rex45 suffers less edge damage than k390. Whether that translates to tougher, I don't know.
I never oil my blades and they cut corrosive materials all the time. They just get rinsed with whatever water is available, and wiped dry. They never rust. This includes 1095 and 52100, which are two of the least corrosion resistant knife steels there are.
I do think Rex is more rust resistant, wonder if it's corroding the edge off
https://knifesteelnerds.com/2019/01/21/ ... retention/
Re: What is tougher?
Posted: Wed Feb 06, 2019 9:29 am
by jpm2
koenigsegg wrote: ↑Wed Feb 06, 2019 9:16 am
jpm2 wrote: ↑Tue Feb 05, 2019 8:02 pm
With my use, rex45 suffers less edge damage than k390. Whether that translates to tougher, I don't know.
I never oil my blades and they cut corrosive materials all the time. They just get rinsed with whatever water is available, and wiped dry. They never rust. This includes 1095 and 52100, which are two of the least corrosion resistant knife steels there are.
I do think Rex is more rust resistant, wonder if it's corroding the edge off
https://knifesteelnerds.com/2019/01/21/ ... retention/
Although I don’t have any trouble with corrosion of Rex or k390, the edges could for sure corrode if not cleaned, dried, and stored in a non corrosive environment.
When I talk about edge damage, I’m always referring to rolling or chipping from use.
Re: What is tougher?
Posted: Wed Feb 06, 2019 10:31 am
by ZMW
JacksonKnives wrote: ↑Tue Feb 05, 2019 11:57 pm
ZMW wrote: ↑Mon Feb 04, 2019 5:52 pm
What is the mechanism to measure toughness, do they put a slab of steel in a vice and bend it? Is it scientific, or just user experience?
Charpy tests are close to that. They use a pendulum to measure how much force is absorbed before fracture. V-notch specimines break a little differently than unnotched or other notch shapes, and it's not a directly comparable test to anything other than prybar use, but it's a good number to know.
Steel mills often release data sheets with charpy test results, but sometimes they're hard to find.
Larrin at knifesteelnerds.com has some great posts about toughness and edge stability, check out his site for sure. He just tested some new samples at different hardnesses and he's building a table so we can see how hardness and toughness relate in different steel structures.
Some surprising info on his site, he shows CPM 154 is far tougher then Cruwear. Everyone says how tough cruwear is, so I assumed it would be much higher in toughness. Interesting... Do others agree with those findings? and AEB-L. Wow
Re: What is tougher?
Posted: Wed Feb 06, 2019 11:31 am
by attila
ZMW wrote: ↑Wed Feb 06, 2019 10:31 am
JacksonKnives wrote: ↑Tue Feb 05, 2019 11:57 pm
ZMW wrote: ↑Mon Feb 04, 2019 5:52 pm
What is the mechanism to measure toughness, do they put a slab of steel in a vice and bend it? Is it scientific, or just user experience?
Charpy tests are close to that. They use a pendulum to measure how much force is absorbed before fracture. V-notch specimines break a little differently than unnotched or other notch shapes, and it's not a directly comparable test to anything other than prybar use, but it's a good number to know.
Steel mills often release data sheets with charpy test results, but sometimes they're hard to find.
Larrin at knifesteelnerds.com has some great posts about toughness and edge stability, check out his site for sure. He just tested some new samples at different hardnesses and he's building a table so we can see how hardness and toughness relate in different steel structures.
Some surprising info on his site, he shows CPM 154 is far tougher then Cruwear. Everyone says how tough cruwear is, so I assumed it would be much higher in toughness. Interesting... Do others agree with those findings? and AEB-L. Wow
I am pretty sure that the Cruwear in that testing was all cast, not CPM. Comparing it to CPM154 is also gonna give us a bigger difference than if it had been compared to regular old 154CM.
CPM Cruwear should be similar to Z-wear on that chart.
The confusion comes from people not specifying if they have CPM Cruwear or just Cruwear. It's kind of like leaving units off of your numbers in science class. Units are important to avoid confusion, and so is the steel manufacturing technology. I trust that Larrin would always specify which Cruwear he's referring to, especially when it's presented as empirical data.
Re: What is tougher?
Posted: Wed Feb 06, 2019 11:55 am
by ferider
ZMW wrote: ↑Wed Feb 06, 2019 10:31 am
Some surprising info on his site, he shows CPM 154 is far tougher then Cruwear. Everyone says how tough cruwear is, so I assumed it would be much higher in toughness. Interesting... Do others agree with those findings? and AEB-L. Wow
For
CPM Cru-Wear, you have to look at the Z-Wear data.
Re: What is tougher?
Posted: Wed Feb 06, 2019 1:18 pm
by Pelagic
CPM154 is great, but with about the same carbon content as (cpm) cruwear and about double the chromium, it can't compare in toughness.
Re: What is tougher?
Posted: Wed Feb 06, 2019 4:11 pm
by bearfacedkiller
ferider wrote: ↑Wed Feb 06, 2019 11:55 am
ZMW wrote: ↑Wed Feb 06, 2019 10:31 am
Some surprising info on his site, he shows CPM 154 is far tougher then Cruwear. Everyone says how tough cruwear is, so I assumed it would be much higher in toughness. Interesting... Do others agree with those findings? and AEB-L. Wow
For
CPM Cru-Wear, you have to look at the Z-Wear data.
Exactly. Cruwear has been around for a long time and has many names. It was once called Vascowear. It has been produced in ingot form and powdered form. The Cruwear in that graph is the ingot version of it. Z-wear, CPM Cruwear and CTS PD1 are all powdered versions of that recipe. The powdered versions will have increased toughness.