Question on AUS 4 Steel

I agree about Buck and their heat treat.It makes 420HC into a very good steel. From what I understand Case SS knives are 420HC and for that matter some Queens and Colonel Coons but then they don't have Buck's heat treat.
 
Lots of knife makers use 420HC. IMO, there is
- 420HC, commonly heat treated to ~55,
- then there's Buck 420HC, heat treated to 58.

I've never tried AUS 4 which has roughly the same amount of Carbon as 420HC and is commonly heat treated to ~56.

Based on that information, I'd put AUS 4 at about the same performance level as most 420HC, though a step below the performance of Buck 420HC. There are some steel manufacturers who include a bit of Vanadium in their 420HC (Latrobe springs to mind), but not everyone does. In the quantities found in Latrobe 420HC (~0.2%) the vanadium serves as a grain refiner and will have no impact on abrasion resistance.
 
Knarfeng
How does AUS 6 and 8 compare to other steels? Would AUS 8 be comparable to 440A? Thanks
 
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No not a CKRT but I do have a Kershaw with AUS 8. Just looking thru the catalog of the well know seller in the south east and that got me to thinking about good and bad steels and how AUS compares to American steels.
 
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IMO it would depend on the heat treat. I've seen several different hardness specs for AUS8, sometimes from the same maker. Some AUS8 knives are 56-57. Others are 58-59. I have one AUS8 blade that I measured at 59. It outperforms the 440A blades I have, but I can't call that definitive, I only have a couple of 440A blades and none is over 56HRC.

I've been told that 440A can be taken to 58-59, but I've never seen a 440A blade that hard.
 
knarfeng said:
IMO it would depend on the heat treat. I've seen several different hardness specs for AUS8, sometimes from the same maker. Some AUS8 knives are 56-57. Others are 58-59. I have one AUS8 blade that I measured at 59. It outperforms the 440A blades I have, but I can't call that definitive, I only have a couple of 440A blades and none is over 56HRC.

I've been told that 440A can be taken to 58-59, but I've never seen a 440A blade that hard.
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With these relatively mid to low end steels, heat treat really makes a huge difference.

Within reason, go with a:
1) knife design you like and that meets your needs... and
2) an advertised hardness Rc58 to Rc59.

At this end of the steel range (relatively simple composition), hardness pretty much defines blade performance... hardness pretty much defines wear resistance..

I'm not a Buck knives fan (no designs I care for), but at least you get a fairly reliable heat treat, a protocol/work process set up by Paul Bos. They pretty much maximize what you can extract out of 420HC.

Anything softer than Rc58 will generally be a disappointment in terms of resistance to edge rolling and general edge retention.

AG Russell's "steel guide" lists a variety of steels and their typical hardnesses... and he's been in the biz a looong time:
http://www.agrussell.com/Steel_Guide/a/73/
 
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winchester73 said:
Knarfeng
How does AUS 6 and 8 compare to other steels? Would AUS 8 be comparable to 440A? Thanks
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AUS 8 is good stuff. It's a reasonable compromise between ease of sharpening and edge retention. Most of us consider it acceptable though not a premium steel.

All I know about AUS 6 is that a friend has a Kershaw in that steel and she's happy with it. She's enough of a knife user to have her opinion respected, but she's not into the fine points.

The 440A, as currently heat treated out of China, is a step down from AUS 8, but still not bad. I can't get quite the edge on 440A I can on AUS, nor does it hold that edge quite as long, but I just don't use a pocket knife hard enough for that to much matter.

IMHO, we worry too much about such matters. The question should not be which is the best possible steel, but whether a knife is good enough for our needs. Any of the steels mentioned are good enough for all but very heavy use.
 
Rob_Angerer said:
With these relatively mid to low end steels, heat treat really makes a huge difference.
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I was sure HT made difference for all steels :) In fact, for high end steels HT being more complicated to achieve max performance becomes more critical. As far as I remembered, you thought so too last time?
 
Gator97 said:
420HC has small amount of Vanadium, AUS4 doesn't, which would affect abrasive wear resistance. There's other differences in composition, but Vanadium is probably more important - 420HC vs. AUS4 steel composition comparison.
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Hi Gator97...

In low concentrations, in the 0.1% to 0.3% range, Vanadium's principal benefit is in controlling grain size during heat treat. Smaller grain size translates to better strength, hardenability, and debatably, easier sharpening.

To realize the wear resistance benefits of the various hard carbides, the concentration of e.g. Vanadium needs to be near the 1% or higher range, to generalize. Examples: D2 is a known wear resistant tool & die steel... and it contains ~ 1.1% to 1.2% Vanadium. ATS-34/154CM contains 4% Molybdenum.

Vanadium is one of 4 principal hard carbide formers of interest in blade steels. Vanadium carbides are hardest, followed by Tungsten Carbides, then Molybdenum Carbides, and lastly Chromium carbides. (Chromium's chief benefit is in retardation of surface and pitting corrosion. There some exceptions, like ZDP-189 where the super high chromium content, 20%, likely means there is enough free chrome left over to form significant chromium carbides, and aid in achieving the very high hardness achievable).

http://www.metallurgvanadium.com/vanadiumpage.html
 
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Gator97 said:
I was sure HT made difference for all steels :) In fact, for high end steels HT being more complicated to achieve max performance becomes more critical. As far as I remembered, you thought so too last time?
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Yep. All true. Heat treat matters. Whether low end or high end steel.

The point is that with mid to low end steels, carbide formation is not a significant factor in blade performance... i.e. carbides are not of sufficient concentration to truly affect blade performance in the wear resistance area (e.g. slicing through abrasive media).

With mid to low end steels, blade performance is dominated by hardness, e.g. Rockwell C scale hardness.

If the manufacturer doesn't advertise blade hardness, you can assume they don't care, don't control tightly for hardness in their heat treating process, or they steel is so cheap that they don't want you to know.
 
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Rob_Angerer said:
In low concentrations, in the 0.1% to 0.3% range, Vanadium's principal benefit is in controlling grain size during heat treat. Smaller grain size translates to better strength, hardenability, and debatably, easier sharpening...
http://www.metallurgvanadium.com/vanadiumpage.html
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Unless I am misreading your link which says: "Class 422. Type 440C and its modifications contain 0.15% V. Both steels rely on vanadium for increased hot hardness and wear resistance.

Which leads me to believe 0.30% V can affect wear resistance, positively.

Plus, several makers stated increased difficulty of machining CPM 154, which has just 0.25% V(allegedly).


Rob_Angerer said:
If the manufacturer doesn't advertise blade hardness, you can assume they don't care, don't control tightly for hardness in their heat treating process, or they steel is so cheap that they don't want you to know.
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Obviously...
 
Gator97 said:
Which leads me to believe 0.30% V can affect wear resistance, positively.
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It does, just not very much compared with it's grain refining qualities at these low concentrations. Gator97, not sure you'd be satisfied unless a maker chimes in here, so my post remains as-stated. It requires no augmentation.

Gator97 said:
Plus, several makers stated increased difficulty of machining CPM 154, which has just 0.25% V(allegedly).
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Versus what? I can infer from your incomplete thought that you meant "versus 154CM or ATS-34."
 
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If you´re using your knife for opening boxes, letters, slice tomatoes, meat and such it will be above ok. My no-name kitchen knives with funky mystery steel works well. I use them everyday and sharpen them maybe once a month.
If you´re planning to use it as a survival knife in extereme condition I´ll suggest you to get a better steel. But for ordenary edc AUS 4 will be ok. It will cut what ever you want to cut.
 
Just a nitpicky note. Finer grain reduces hardenability, not improves it. For stainless steels its probably a mute point, but generally speaking as grain size goes up, hardenability goes up.
 
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