Just got my CPM M4

cotdt have you considered trialling carpenter's micromelt maxamet alloys?

Its interesting in that it offers abrasive wear resistance close to cermented carbides while providing heaps more toughness. Plus a HRC 70 knife is just cool :)
 
nullack said:
cotdt have you considered trialling carpenter's micromelt maxamet alloys?

Its interesting in that it offers abrasive wear resistance close to cermented carbides while providing heaps more toughness. Plus a HRC 70 knife is just cool :)
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I would if I knew where I can buy it without having to buy 2 tons =) The closest I can get is Crucible's CPM 121. I love these really hard steels, useful for doing artwork. They last forever.
 
wow this is an old thread (compared to how long Ive been on here)

I vote we just turn this one into anything related to CPM M4 which we pretty much already did anyway.
cotdt thanks so much for the data I am planing on making a couple of 3.5" neckers for sure, and I want to take it up to 65 Rc so, lets consider the heat treat
My question is and this goes for most steel, should you austenize at a higher temp and then temper at a higher temp, or austenize lower and temper lower for the same Rc

and secondly is interupted oil better than plate quenching. you could put the bottom plate into water to cool it if it is small enough that it gets quite hot.
 
Troop said:
I've got some coming in a couple of weeks:). How many seconds did you leave it in the oil before you pulled it to let it air cool? Do you think that going all the way to 66 HRc would reduce the toughness too much?

http://www.crucibleservice.com/datash/dsM4v8.pdf?CFID=668056&CFTOKEN=58644781

- Thanks
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I used slow oil, at room temperature, so I was dipping it in and out for a full 10 seconds before it was barely glowing. Crucible datasheets say that at 65.5 rc, CPM M4 still has 27 J of impact toughness which is about the same as most stainless steels at 60 rc. At full 66 rc, I don't know, it's only a half point harder, might still be pretty tough.

Nebulae said:
My question is and this goes for most steel, should you austenize at a higher temp and then temper at a higher temp, or austenize lower and temper lower for the same Rc

and secondly is interupted oil better than plate quenching. you could put the bottom plate into water to cool it if it is small enough that it gets quite hot.
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Research papers show that for high speed steels, you get better toughness using a lower austenization rather than full austenization and tempering down. However, less carbides dissolve so you might get a little lower wear resistance as well.

For plate quenching, you usually leave the unground blade blank in the foil and press between the plates. This wouldn't work for me because grinding hardened M4 would eat up all my belts. Interrupted oil didn't warp any of my blades but plates are the safe bet for thinner blades. You can also quench M4 by putting it in front of a fan.
 
ah thanks, see I was operating under the assumption that you would plate quench a finished blade, but since my bar is kinda thick a short knife would have to have a distol taper and I was wondering how plat quenching would work with a taper. yes I cant imagine grinding M4 at 65 Rc
 
Nebulae said:
ah thanks, see I was operating under the assumption that you would plate quench a finished blade, but since my bar is kinda thick a short knife would have to have a distol taper and I was wondering how plat quenching would work with a taper. yes I cant imagine grinding M4 at 65 Rc
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I've found that those aluminum plates are really fast, so they would probably work even with a grounded knife. With M4, you have basically 3 whole minutes to reach below 1000F. There are many ways to quench it.

I can do your heat treating now. My original recommendation to you for Texasknife was bad, they use 321 stainless foil which doesn't work for the high temperatures M4 uses. Now you just need to figure out how to grind that 1/4" stock! I've done 1/4" stock A2 and would never want to work with anything that thick ever again.
 
cotdt said:
Grinding annealed CPM M4 was very easy, slower than grinding 1084 but not bad at all. I used a Dremel and $60 belt grinder, but it can also be done with just hand tools.

Experiment #1: 1.5" blade, CPM-M4
=================================
-2175F austenization, pencil-coated, soaked 5 minutes
-oil quenched to dull red, cooled to r.t. in still air. Got zero warping (yay).
-1020F triple temper straight away, 2 hours each
~65.5 rc

Success. Sharpened blade to 9° per side and did not notice any chipping carving hardwood. I used it to scribe grind lines onto steel blade blanks, cut ...............................................................................................
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What is the "pencil-coat" you used?


Regards Jakob
 
Nylunds knives said:
What is the "pencil-coat" you used?


Regards Jakob
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I just used a pencil to coat the blade in graphite, which is carbon, to counter decarburization. I was afraid that using stainless steel foil would stick to my blade in the near-2200F temperature used. In my 2nd and 3rd M4 knives I just used 309 stainless steel foil, and it worked fine.
 
cotdt said:
I just used a pencil to coat the blade in graphite, which is carbon, to counter decarburization. I was afraid that using stainless steel foil would stick to my blade in the near-2200F temperature used. In my 2nd and 3rd M4 knives I just used 309 stainless steel foil, and it worked fine.
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Okay, is that all it needs to protect the blade from decarburization?

That is way easier then folding the damn SSfoil.
 
hey the graphite sounds like a terrific idea, but i though that decarb was not a big issue with M4 partly because it doesnt require very long soak times, but really that is easy to do, and since the heat treating process as a whole is so important it sounds like a very good idea
 
Nebulae said:
hey the graphite sounds like a terrific idea, but i though that decarb was not a big issue with M4 partly because it doesnt require very long soak times, but really that is easy to do, and since the heat treating process as a whole is so important it sounds like a very good idea
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That's what I thought too, but then I read a paper showing rapid decarburization with M4, simply because of the alloy makeup. Interestingly, T15 actually carburizes. Well, the main issue is scale. Without the stainless foil, you still get some scale that must be ground off, so I went back to using stainless foil.
 
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