M4

Walt2

Walt2

Joined
Mar 13, 2001
Messages
1,157
Looking for someone with expereience with M4. Does it work harden? Sure seems like it. Also what is the recommended hadness when getting it tempered? Thanks for any info
 
I watched a guy HT one I think the recipe was 1985 degrees for two hours quench then two one hour draws at 1000 degrees and he was suposed to be 63rc he loved the stuff and I'm amazed that I remembered that never worked with it myself hopefully he will stop by his name is Donavan
 
As far as I know all metals work harden. You can harden it anywhere from 60-66 Rc, depending on the application.
 
Heat Treat Response
Hardness HRC
Austenitizing 1875°F 1975°F 2050°F 2100°F 2150°F 2200°F
As Quenched 59.5 62.5 64.5 65 65 63.5
1000°F (540°C) 58.5 61 62.5 63.5 65 66
1025°F (550°C) 58 60.5 62 63 64.5 65.5
1050°F (565°C) 57.5 59.5 61 62 63.5 64.5
1100°F (595°C) 54 56 58.5 60 61.5 62.5
1150°F (620°C) 50 53 55 56 58 59
1200°F (650°C) 44 48 51 52 54 55
Results may vary with hardening method and section size. Salt or oil quenching will give
maximum response. Vacuum or atmosphere cooling may result in up to 1-2 HRC points lower.
Minimum Time
at Aust. Temp. 45 min. 30 min. 20 min. 15 min. 10 min. 5 min.
Minimum Number
of Tempers 2 2 2 3 3 3

For a much more readable version:

http://crucibleservice.com/datash/dsM4v8.pdf?CFID=1993505&CFTOKEN=21185913
 
got a bunch of steel i was told was m2 is there much difference?? never really made no knives w/it, mostly just jigs, and file guides.

seems like alot of work to ht properly, are the results worth the trouble?

andy
 
CPM-M4 is tougher and more wear resistant than M2. M2 is a good steel, though I consider CPM-M4 an upgrade. Other than the high austenitizing temperatures it's not harder to heat treat than any other air hardening steel.
 
Yes it's their steel . Just look under CPM steels , high speed steels. On the other hand M2 is found under knife steels.That might be a hint that CVPM M4 is not appropriate for knives !
 
made a small necker sized skinner out of cpm m4 and have about one more small blade worth to play with. im betting that the skinner doesn't need much sharpening in its lifetime (tho when it needs it you should have DMT stuff)

oo i ran it at 2100f plate quench and 1000f tempering

like all the super alloy stuff get it where you want it before heat treat and make sure you have a good foil pack. grinding after heat treat sucks with anything short of gator and norax Sp? belts
 
Two things I've wondered about M4 are how fine an edge you can put on it before carbide pull-out becomes an issue, and whether or not it would make sense to austemper it.
 
M4 is air hardening ,I don't think it's suitable for austemper. Crucible makes both standard M4 and CPM M4. For knives make sure you get the CPM version then carbide pull out won't be a problem and it will be easier to grind and sharpen.
 
Roman Landes seems to think that CPm-M4 would have very good resistance to carbide pullout, the carbide structure is pretty good, I wouldn't worry about fine edges.

I've seen some literature on austempering high speed steels, and it seems you could get around 50% bainite. However, it takes long periods of time and I don't think the results would be worth it.
 
The general consensus seems to be that you had better not have any plans to put any kind of fine finish on it once it is hardened because you are going to be VERY frustrated trying to sand it.:D
 
I bought one one 1/8"x11/2"x36" piece from Crucible. I will have Paul temper the blades if I ever get around to getting them done. I was trying to get a feel for the preferred hardness between 60-66, because of the expected difficulty in sharpening. I am playing with this just out of curiosity. I have one person that I have made 3 knives (S30V, 3V, and D2) for who does a "lot" of skinning and quartering deer during season and he is always wanting something that holds an edge better than what he already has. He may wind up with one of these M4's
 
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I would say for a skinning knife you should go fairly hard, 63-64 Rc or higher, depending on whether or not the customer uses the knife for tasks other than skinning (prying apart bones, etc.).
 
Thanks Larrin, that is what I was looking for. I have absolutely no experience with this steel and have only seen just general references to it in discussions.
 
Walt2 said:
I was trying to get a feel for the preferred hardness between 60-66, because of the expected difficulty in sharpening.
Click to expand...

Get the edge geometry ground nice & thin, and sharpening won't be an issue even at max hardness. Just use diamonds or ceramic. The harder it is, the less it will be prone to forming burrs at the edge, which are even more time consuming to remove than the primary sharpening takes.
 
I agree with the possum.

By the way, my recommended heat treatment would be 2125F austenitizing temperature and 1050F temper which would be approximately 63.5 Rc. If the customer assures you he does nothing but cut with the knife (as opposed to prying) than I would consider taking it to near max hardness by using 2200F and 1050F, which would be approximately 65.5 Rc. If he says that he does a considerable amount of prying than I would take it down to 62 Rc using 2000F and 1025F. The hold times for these temperatures can be viewed in the data sheets.
 
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