Charpy results for ZDP-189

Larrin

Larrin

Joined
Jan 17, 2004
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People are saying that ZDP-189 is just as tough as anything else, but Hattori's own website says otherwise: http://www.hatta.co.jp/zdp.html The bottom has a little thing that says charpy (in Japanese), and then compares the ZDP at 67 Rc against ATS-34 at 60Rc. The ZDP is less than half as tough. My guess is that at 66-67 Rc it isn't exactly easy to sharpen either. I'd say S90V is still the king of edge retention, much tougher, and I'd guess both are equally hard to sharpen. Sal Glesser also said in another post that S90V and ZDP were right together on the CATRA test.
 
I'm betting Sal isn't going to ship any ZDP-189 blades hardened anywhere near 67 Rc. I would be surprised if they were over 61 Rc. That should improve the Charpy dramatically.
 
I'm pretty sure the Charpy test is a rating of impact resistance. It would only make sense that 67RC ZDP-189 would get a lower score than 60RC ATS34.

I'm sure that is why the only things that I've seen in ZDP-189 have been laminated.
 
But when Sal did the CATRA test it was way up there in hardness (can't remember what it was), so when it's lower, it wouldn't be able to match up with S90V. A laminate doesn't stop any chipping in the blade.
 
ZDP198 is hardest and YXR7-toughest. ZDP-189 is not tough according to YSS steel chart.
And this is from the table came with this chart:

Steel/Corrosion resistance/Wear resistance/Toughness/HRC
440C/A/B/B/57-59
ZDP189/A-/A+/B-/65-67
YXR7/C/A/A+/61-65
ATS34/A/A-/A-/59-61

So ZDP189 according to YSS data sheet less tougher then 440C and much less then ATS-34.

Isida-san http://www.isd-ishida.co.jp/English/SUS/knife.htm for example
make layered blades with ZDP189 in core and ATS-34 on the sides. However YXR7 is mos promising steel.

YSS - Yosoto Steel Special, top grade steel producer for custom knifemakers in Japan (Hitachi Metals).

I'll put this chart on my website sometime.

Thanks, Vassili.
 
Larrin said:
A laminate doesn't stop any chipping in the blade.
Click to expand...

No, but it does mean that the blade as a whole shouldn't be any more brittle than another steel.

Sure, the edge may be more likely to chip, but what do you expect at 67RC?
 
Steven Roos said:
No, but it does mean that the blade as a whole shouldn't be any more brittle than another steel.
Click to expand...
I like laminates too, I was just very disappointed in the toughness of ZDP. I think S90V is a better overall steel, and you can actually buy S90V in America. ZDP is only available in Japan.
What is the YSS steel chart? I'd like to see the rest of it. According to the charpy value given, I wouldn't put ZDP at B-, I wouldn't have it any higher than C-.
In the quick research I just did, YXR7 looks like a coating, like Titanium Nitride and similar other hard coatings they put on razor blades (for longer-lasting blades) and some knives (for looks, mostly). Are they putting it on the actual edge?
 
No, this is steel, the other data from this chart
YXR7 - "matrix high speed steel"
Annealing -800-880C slow cool
Quenching - (1)1160-1180C (2) 1120-1160C oil
Tempering - 540-580C air
ZDP247 is close by YXR7, but bit less tough and bit less hard

Thanks, Vassili.
 
Charpy is an impact test striking a notched block with a weight until it breaks. All it shows is that, as one would expect from such a hard steel, is that it is brittle when raised to that hardness level so you don't want to go making machettes or hammers out of it. L6 or S7 would be much better for that. But, that doesn't matter if you are making a little bamboo carving knife (bamboo contains silica and dulls and scratches softer steels) or a good long lasting slicer.
 
Hattory making KD -line of knives with laminated blades - CovryX in core and Damascus sides.

Thanks, Vassili.
 
yuzuha said:
Charpy is an impact test striking a notched block with a weight until it breaks. All it shows is that, as one would expect from such a hard steel, is that it is brittle when raised to that hardness level so you don't want to go making machettes or hammers out of it. L6 or S7 would be much better for that. But, that doesn't matter if you are making a little bamboo carving knife (bamboo contains silica and dulls and scratches softer steels) or a good long lasting slicer.
Click to expand...
I know what the charpy test is. I posted this because the Blade article on ZDP said that it was just as tought at 67 Rc as anything else is at 60 Rc, according to the charpy test, this is far from true. What I want to see now is what it gets in the CATRA test at lower hardnesses.
 
Didn't mean to imply that you didn't... I was just thinking that I don't know how exactly "toughness" relates to impact resistance. Asphalt is very malleable and can be bent and twisted without breaking, yet strike it sharply and it will shatter like glass. To me, toughness also includes resistance to bending as well as resistance to breakage on bending as well as impact reistance (ductility, strength and malleability combined in some subjective way). I'd think their rating kind of depends on how they define "toughness".
 
If you have not already done so, pick up one of the Rockstead knives at BLADE and test the sharpness. It is mirror polished to zero, and it is unreal sharp!
 
I don't know. This seems to me like comparing apples and oranges. Edgeholding is both a function of abrasion resistance and hardness. Even if S90V is as abrasion resistant as ZDP-189 but not as hard, its edgeholding will be much inferior for many applications. I don't know what happens to S90V when you run it at Rc67, maybe it becomes like glass and unusable as a blade steel. In that case you really can not compare S90V and ZDP-189 at very high hardnesses. I don't think the claim was made that ZDP-189 could be hardened without any loss in toughness. I read it more as being still of useful toughness at rediculus hardnesses. I doubed that ZDP-189 will ever become a factor in large fixed blades or any other application where toughness becomes more important than edge retention.
 
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