CPM M-4 question

Stacy E. Apelt - Bladesmith

Stacy E. Apelt - Bladesmith

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I am going to start experimenting with CPM M-4. I am thinking of making some of my higher end user cutlery, like sushi and fillet knives, from it. I am wondering who uses it now and about the temps that result in the best toughness/hardness ratio.
After ramp up,I plan on 15 minute soak at 2100F and temper three times at 1050F. That should yield a very hard and tough blade that will hold up to soft tissue cutting (fish/seafood and vegetables).The edge retention should be fantastic. Target Rc of 62-63. Quench will be in 1000F salt, then transfer to plates.
The blades will be .100 to .140 thick and I will take the edge to .015-.020 prior to HT. Grinds will be either flat or Japanese (chisel) grind .

Any advise from those who use this steel? (Besides doing all the grinding possible prior to HT).

Also, anyone tried high austenitic temps and lower tempers. ie. 2200F and 1000F ? If I read the data right the hardness will top at Rc66 this way. And that is the TEMPERED hardness ! How does the edge hold up at this hardness?

I expect I'll have to do a good bit of trial and error, but since it is a tad expensive, I thought I would start with any procedures that you know work (to shorten the learning curve).
Stacy
 
All I have heard about the use of cpm M-4 is at lower RC's. Cpm-M4 is able to be ground super thin prior to the secondary edge bieng put on. This combined with good edge retention (even at rc58) and incredible impact resistance. If you are going to go to a super high rc you may be missing the best benefit of the steel. The ability to hold an incredible edge at a softer RC still allowing great impact resistance. The rep from crucible suggested 58-62.5, the low ball of 62 you gave would be as hard as I would want to get it.

As a non stainless steel I would want something else for fish or kitchen knives. Carbon steel knives are ok in the home kitchen but in food service I simply dont have time to maintain my knives past sharpening. also the super low grindability of CPM-M4 would mean you would have to have a super thin edge on it and reprofilling would be a pain.

Mayeb a maker who puts this stuff to more use (to expensive for me atm) can give more/better input but thats my 2 cents.

Edit: I know a good sushi knife is usually a high hardness knife, but m4 is so expensive I dotn know if that hardness would be lessening its value by giving up one of its main attributes.
 
Thanks, Big Jim
I was originally going to do it in the Rc60-62 range. According to Crucibles info, the max toughness and hardness are in the upper range ( the 62.5 is what I rounded to 62-63)
Many sushi chefs either don't like or won't use a stainless knife at all.
I get away with CPM 154 because it doesn't look stainless. 1095 works well, but has to be re-sharpened too often. Proper wiping, cleaning, and care are the keys to non-rust problems with professional cutlery.

Thanks again,
Stacy
 
i may hav eot jump in on some of this next time i order steel as i have some requests fo a high carbon high ware steel fo a few of my knives
they told me there not worried about if it ever needs to be sharpened (there up to the challange :) )
 
Hi Stacy,
I've been experimenting with it some, only because I got a bunch of it for 50 cents a pound. :D
The last batch I did, I soaked at 2000 for 40 minutes, plate quenched, (sort of. I put it on the baseplate of my air hammer and put another steel plate on top and stood on it.) then tempered 3 times, first at 1000, then 1025, then I finally ended up at 1050 for a hardness of 60-61. According to the data sheet, I should have gotten an as-quenched hardness of 62-63, but it was actually 65.
Even at 60 RC, this stuff is very difficult to hand sand.
 
I could see that a Sushi chef would probably have alot easier time maintining there knives. Damn european kitchens are hell on knives. They became all sorts of improptou tools and we often had to drop our knives and go do other things. As a matter of fact, those damn sushi chefs get to stand there cooking and I even buy them shots of saki! Who the hell talked me into european cuisine! ><
 
Phillip Patton said:
Hi Stacy,
I've been experimenting with it some, only because I got a bunch of it for 50 cents a pound. :D
The last batch I did, I soaked at 2000 for 40 minutes, plate quenched, (sort of. I put it on the baseplate of my air hammer and put another steel plate on top and stood on it.) then tempered 3 times, first at 1000, then 1025, then I finally ended up at 1050 for a hardness of 60-61. According to the data sheet, I should have gotten an as-quenched hardness of 62-63, but it was actually 65.
Even at 60 RC, this stuff is very difficult to hand sand.
Click to expand...

WOOOOOOT?!?!?! 50 cents a pound? a 3' section is over $100 bucks, thats damascus prices right there. I am sooooo jelous. MAke shure you bust out a competition chopper!
 
BigJimSlade said:
WOOOOOOT?!?!?! 50 cents a pound? a 3' section is over $100 bucks, thats damascus prices right there. I am sooooo jelous. MAke shure you bust out a competition chopper!
Click to expand...


Well, don't be too jealous. It's not exactly ready to use. What I have is used broaches, which I guess they use for making gears or something. I have to first anneal it, then cut it in half (they're 30" long, and 1-3/4" in diameter)
then grind the teeth off, then forge it flat. But at 50 cents a pound, I can handle it. :D
 
Thanks Phil, I will go with the start I planned and move down to your temps.
40 minutes seems a bit long for 2000F? I would think 20-30 was more than enough.
Stacy
 
bladsmth said:
Thanks Phil, I will go with the start I planned and move down to your temps.
40 minutes seems a bit long for 2000F? I would think 20-30 was more than enough.
Stacy
Click to expand...

I'm not sure why my hardness readings were to much higher than what the data sheet says.
Austenitizing at the lower range will give you less RA, more toughness, and a little less wear resistance.
Here's the data sheet in case you don't already have it:

http://www.crucibleservice.com/datash/dsM4v8.pdf?CFID=1221095&CFTOKEN=83511457

It says to soak for 30 minutes at 1975, 20 minutes at 2050. I picked 40 minutes because it's about the halfway point.
 
To answer the question, sometimes a lower austenitizing temperature with a lower temper can give a higher toughness than a higher temper with a higher austenitizing temperature. Having less carbon in the matrix from the lower austenitizing temperature increases toughness. I wouldn't use a lower temper than 1000F.
 
Phil, I must be missing something here. How is 40 half way between 20 and 30?

My rep sent me the data sheet and the tech guys said to go with the higher temps. They implied that in a thin section,like a blade, the soak need no be overly long. The toughness does increase quite a bit with slightly lower hardness in the 62-63 range. The best should be at 2100F/1050F HT, from what they said and I calculated. What I really wanted to know from anyone who is actually using this steel, is how the edges hold up at that high hardness.
Stacy

Stopped snowing, maids just left, going to the forge! Bye.
 
bladsmth said:
Phil, I must be missing something here. How is 40 half way between 20 and 30?

My rep sent me the data sheet and the tech guys said to go with the higher temps. They implied that in a thin section,like a blade, the soak need no be overly long. The toughness does increase quite a bit with slightly lower hardness in the 62-63 range. The best should be at 2100F/1050F HT, from what they said and I calculated. What I really wanted to know from anyone who is actually using this steel, is how the edges hold up at that high hardness.
Stacy

Stopped snowing, maids just left, going to the forge! Bye.
Click to expand...

Oops, you're right! I never claimed math was my strong suit. :o:D
Still, I don't think soaking that long at 2000 will hurt it.
Actually, I might be remembering wrong. Maybe I soaked it for 30 minutes... :confused:
Anyway, it ended up at 60-61 RC, and very wear resistant.
 
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