Need Information On ZDP-189 Steel

T

TPU

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Feb 25, 2003
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With all these new blade steels comming out, could some of you experts tell me about ZDP-189 blade steel. How does it compare with S30V, VG10, and 154CM. I notice that Spyderco is using it on their Delica, and its about $40 more then their VG10 steel. What makes it so much better? Thanks,
 
It gets very very hard, around RC 63-68, depending on the manufacturer, and isn't terribly brittle at that hardness.
 
From what I've heard about the characteristics of the steel it should be able to take a very sharp edge and hold it better than the other steels you mentioned. Just remember different steels work better for different applications. ZDP-189 would probably be a poor choice for a large knife that would see a lot of abuse. It sounds like it is more suited for smaller blades that will be used frequently for cutting things, but aren't going to be used for chopping, digging, prying, etc.
 
A Hitachi steel with 3% carbon and 20% chromium. Supposedly has some specialized heat treating that Hitachi keeps secret, but that could be just the usual virgin read-head urine quench.

See also:

http://www.bladeforums.com/forums/archive/index.php/t-362535.html

Whups. Looks like the heat treatment isn't secret any more, and no red-heads were harmed in the quenching of this steel.

http://www.discipleofdesign.com/knives/ZDP189_eng.pdf

And, if you go here, you'll find a couple of informative reviews of knives with ZDP-189.:)

http://www.cutleryscience.com/reviews/reviews.html

Cliff, the Charpy rating for ZDP-189 at RC 67.5 was about a third of ATS-34 at RC 60. At what point would this be a meaningful distinction? This is more of a question about mapping Charpy to real-world behavior than anything about ZDP-189.
 
I'm not Cliff (I seem to be adding that disclaimer a lot lately) but I am somewhat confused. I've seen many references to the Charpy test numbers for various steels used for blades. I have also read in ASM Metals Handbook-Tool Steels that for hardnesses in the range knives are typically fall (58 and up) that the torsional impact test gives more reliable and repeatable results. If I am not mistaken, ASM says that Charpy tests are not recommended because of variability, problems with the machines not being rigid enough to provide repeatable tests, and some other issues I cant remember now. Perhaps this only applies to tool steels, but the way it was worded, it seemed intended for tests at high hardness in general. The same problems and some others also applied for tensile tests on very high hardness samples. For this reason a torsional strength test was recommended.

"Cliff, the Charpy rating for ZDP-189 at RC 67.5 was about a third of ATS-34 at RC 60. At what point would this be a meaningful distinction? This is more of a question about mapping Charpy to real-world behavior than anything about ZDP-189."

To more directly answer the question (that was not addressed to me), that seems like a very wide gap with no information in the middle. I would think you really need a range of measurements in between to make any real comparisons. There could be peaks or valleys in toughness that wont show with just one test (or with Charpy tests in general, see above). Of course the one thing those tests do tell is how the steels behave at the commonly used hardnesses (I'm assuming 67.5 is a representative hardness, having never used any ZDP-189). The heat treating information would be nice, as the same hardnesses can be reached in different ways.
 
but cliff knows his shit.. gabe it means if ya got a big chopper it needs only 1/3 as hard blow as ats to break. zdp is not intended for big blades (unless you make them very thick) but strength is a function of hardness so if you stay below like 5000-5500 or so mpa (newton/mm2) youre safe (talking static stength), but fast poweful impacts is not good for high hardness steels iirc. i´d say the perfect use for zdp is a victorinox type of knife, small, thin, allround slicer but hey im not a metalurgist (mete is tho, ask him)

me personally id like a mora zdp to abuse to the max (since thats pretty much what i do while working) and see how it holds up, preferably @max hardness
 
iirc the charpy tests are really accurate and you often do several just to make sure, but a charpy test is not the whole truth, there are lots of other parameters to consider also, but most important is your intended use of the knife, then you choose steel and hardness, but if you want really really good performance you have to go custom (since a good heat treat takes time cost alot of money since its done "manually" and usually cant be be massproduced, i mean many blades all at once you know)
 
Gabe Newell said:
Cliff, the Charpy rating for ZDP-189 at RC 67.5 was about a third of ATS-34 at RC 60. At what point would this be a meaningful distinction?
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If you hit the blades with, or used the blades to hit, a hard object with a high velocity.

me2 said:
There could be peaks or valleys in toughness that wont show with just one test (or with Charpy tests in general, see above). Of course the one thing those tests do tell is how the steels behave at the commonly used hardnesses (I'm assuming 67.5 is a representative hardness, having never used any ZDP-189). The heat treating information would be nice, as the same hardnesses can be reached in different ways.
Click to expand...

Yes and yes. Spot numbers are useless as are numbers with no details. Actual materials testing, as in what is published in tool steel books, will tell how the steel was hardened. Most testing of the above type is highly selected promotion material by the salespeople who are promoting the steel. There are many ways to test steels for various properties so they do them all and then pick the one that has the best result and then promote that as the most meaningful. Crucible did this with S30V and the parallel toughness testing with overpromotion that S30V was A2 level in toughness origionally.

Carpenter does a nice job on presenting toughness in their steel book as they show complete temper responces for various tests and are clear that on the high hardness steels this is only an *estimate* because such steels are very notch sensitive and you can never use them as people commonly do on Bladeforums, i.e., 16 ft.lbs < 20 ft.lbs. Comparing physical measurements is more complicated than that. Essentially what you have to do is |16-20| <> e, where e represents the combined physical measurement uncertainty in the results, this is very large for charpy type testing on those steels.

M Wadel said:
i´d say the perfect use for zdp is a victorinox type of knife, small, thin, allround slicer b...
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Exactly right.

-Cliff
 
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