NEW Steel FAQ

The above sections provide a wealth of information, reading this would solve a lot of problems, and cut through a lot of promotional hype. In the properties selection you might want to add a reference to ductility which is important to durability in both a gross sense (the knife snapping in half) as well as preventing edge tears and the like.

[snip excellent overview]

Corrosion resistance can also be a large factor in edge retention.

Just a comment here, CPM-10V has slightly better toughness than D2, though I would agree that it isn't a good choice for high toughness applications.

[SNIP]

I have soaked it, Ed Schott heat treatment, no significant pitting, far less than ATS-34 and the like (VG-10, D2, etc.) which pit very badly.

'420HC' is actually a name like Carbon V in the sense that it applies to a family of steels. It just means AISI 420 with more carbon, the range of carbon can be quite high, on the extreme end the steel can be 58 HRC after tempering (Camillus / Buck) which puts it pretty much right on top of 440C. Most use lower carbon versions however and the hardness is ~ 55 HRC.

Some comment on max hardness might be useful here (and in general), BG-42 and S90V can get 1-2 HRC points higher than S30V.

This is a bit dated, its time it passed, no one will use BG-42 with S30V now available, the promotional advantage of S30V, the 'hotness', is simply too great.

[SNIP]

and now to S30V.

[snip]

and soft, yes you have already clarified the relation ship between hardness and strength in the above, however I would still note the much lower working hardness of the Cobalt alloys, ~45 HRC for most, even lower for Boyes.

Man that is tough to find information on 'stainless and heat resistant steels' (usually abbreviated to just 'stainless steel', I couldn't find any worth anything. It's like it's not important to industry, how strong it is or how good it holds an edge, since it's usually not used that way.

Tool steels, on the the other hand, are all about comparisons of their strengths and weaknesses and their edge holding ability. Tool steel is easy as anything to find detailed comparisons on.

That is so true sounding to me, I can hardly believe I'm reading it and not spewing it for a change!

YeeeHaaaw! And most of the makers of fancy high dollar knives prefer L6 for their own personal knives. It holds an edge ever bit as good as stainless steel and is so much stronger they can make the knife edge thin and sharpened sorta like a straight razor. These are the same guys that make and sell stainless steel knives too.

This is soooo cool Joe!

Is that true? :/ If so, looks like I'm going to have to get some S30V and hand it over to my 'testers'.

Something I want are numbers showing a comparison of S30V and O1 (or any 'tool steel' in strength at various tempering temperatures and the hardensses that go along with them. Now that would be cool. I wonder if Carpenter would release those numbers to us? They already have them, it's just a matter of them letting us see them.

Hmmm... Yeah but, hardness has a big part to play here too.

Sometimes minor, but sometimes the only thing that counts, no kidding.

It's hard to find real numbers on 'wear resistance' tho since it's hard to measure. Most (98%?) of the information out there about wear resistance is in the various steels' annealed condition. Like 4340 being way more wear resistant then 1095 is an example that messed me up in my early days researching knife steels.

Cool! And something like L6(4370) with Ni strengthening the iron directly by 'solid solution' is pretty hard to beat. But Ni has it's problems, if there is much in the way of other alloying, so just like Cr, too much, is still too much. Just right is still just right and Cr is one of the best steel alloying elements we have.

L6(4370) or 0186(8670 modified) can be heat treated to a hardness that's next to imposible to file (63hrc), so you can have both properties in the same steel.

Joe, please delete: 'Present in most cutlery steel except for A-2, L-6, and CPM 420V.'

Joe, please delete: 'always have 1% or more molybdenum

Thanks for the comments Alvin. I'm going to look them over, especially the 'please remove' parts. I'm pretty sure I had at least one, and maybe more cutlery steel charts in front of me at the time I wrote that. Gotta go back and double-check!

[toughness of S30V]

Based on what I have seen, tests I have read, and the materials data collected by Crucible which show it has the same impact toughness as 440C, it isn't anything special in that department.

Consider this thread :
http://www.bladeforums.com/forums/showthread.php?s=& threadid=262446

The maker won't even use 15 degrees for a kitchen knife. I run axes at that angle. It also breaks *really* easily, has almost no ductility.

If you want a stainless cutting steel use S90V which can get to 62/63 RC, and has a very high wear resistance, more than twice than of 440C, and a toughness inbetween 440C and D2.

The makers who are hyping S30V for toughness are the same guys who said the same thing about ATS-34 and would use it in axes, machetes, swords etc. .

[Thanks, I'll check it out with all the others I need to read when I get a chance ;]

Oh heck, I was hoping for more strength than that from PM products.

I don't want stainlessness just hoping for one that finally measures up to the ingot/wrought carbon steels is all. :/ When a guy braggs on his new knife being stainless steel and good both, I was hoping I could, someday, finally agree with him!

Alvin in AZ

98% of my post was just me getting carried away and not written for the faq really.

Don't believe 'cutlery charts' for anything ok? Lots of mistakes have gotten copied and re-copied along with ommisions 'showing up' too.

Ooops. :/ 52100 is like L1. (not W5) 50100 is like W5. 50100-B is like W7.

That information makes it easy to compare them since there's lots of information about tool steels out there and since they are in the information business instead of the knife business the writers (metallurgists) are easier to trust?

Alvin in AZ

According to Crucible, CPM-1V has the impact toughness of S7 at a slightly higher hardness and the wear resistance of A2. CPM-3V has twice the impact toughness of A2 and the wear resistance of D2.

Holy cow! S7 is -the- tool steel to beat for toughness/strength. S7 is used to make jack hammer bits! But it's too soft for a good edge holding knife blade. So CPM-1V is as strong as S7 and as hard and wear resistant as A2? Holy cow.

A2 for me, has always been thought of as the high end of alloying content before certain bad traits start to show up, like grain coarsening and other strength problems. Looks like that's been passed up big time.

How 'stainless' are CPM-1V and CPM-3V tho?

I need an updated tool steel book that includes the new P/M steels. Almost all of them listed in my books are HSS versions and only two that aren't a D2 version and CPM-10V (they use a space and leave out the hyphen). CPM-10V looks like a P/M version of A7 only with double the V content. But that's the P/M tool steel section.

MPIF, Metal Powder Industies Federation is what I need to check out.

MPIF's F-0008, ASTM's B-310, class C, SAE's 853 class 3, ...is a P/M high carbon low alloy steel .6% to 1.0%C.

There are two other class's a .3%C max that they call 'P/M iron'. And a medium carbon steel .3% to .6%C class that MPIF calls F-0005.

All the rest are high copper steels with as high as 25%Cu obviously for use as sinthered bearing and gear parts.

Do I sound out of date?

Alvin in AZ

Just to correct myself, Jerry Hossom came out awhile ago promoting CPM-1V as having twice the toughness of S7 at a higher hardness and the wear resistance of D2. This claim was challenged, and the abilities of the steel kept being reduced in a scramble to return to sanity. Last I checked it was as I described in the above.

However I just rechecked the spec's from Crucible on their website and now CPM-1V has the wear resistance of A2, but 90% the toughness of S7 at the same hardness - 56 HRC. CPM-3V is still pretty good, at 62 HRC it has the toughness of A2 at 60 HRC, and has a wear resistance exceeding D2 - according to Crucible. Ref :
http://www.crucibleservice.com/datash.cfm

No experience with 1V. 3V doesn't patina as fast as something like L6, 52100 etc., but can't withstand salt water soaks for long. Damage is minimal with soaking though, it doesn't pit rapidly like the pseudo-stainless steels like