CPM Question

S

smorgan345

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Mar 8, 2007
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CPM is just a process Crucible uses to create it's steel correct? Is it better than other steels of the same type? For instance, I can buy straight D2 or CPM D2. Is one better than the other in terms of performance of the finished product? Do they heat treat the same? Thanks for any input.
S
 
CPM stands for "Crucible Particle Metallurgy", and refers to the process
they use. Other companies have particle processes too, but may vary.

Yes, CPM D2 performs better, and at least in my shop, it responds
more favorably to HT.
 
many times you will see 1-2 points extra hardness on PM steels over there non PM "alloy"
also at the higher hardness they often act as tough as if they were 1-2 points softer

so if you want you can kind of read that as getting a "free" 1-2 points of hardness without giving up the toughness
 
I will give you this analogy. If you take a big scoop of sand and rocks from the river and make concrete....there will be large and small rocks in it....and they will be distributed randomly. Some places the concrete will be ( literally) rock hard, and some places softer. The structural strength will vary ,too. It will be hard to smooth out, and will look bumpy.

Now if you take fine, sifted sand,and do the same thing...the concrete will be smoother, have even hardness and strength...and finish much easier.

In (C)PM steels, the steel is reduced to a very fine dust and fused together to make a 100% compression ( no voids). This evenly distributes the carbides and alloy ingredients, and yields a small grain size. The resulting blade should have less edge chipping, a smoother surface ( polishes better), and much less chance of a failure following a large grain boundary.

When available, CPM is always the better choice.

Now, all that does not mean that a non-PM blade is junk. ATS-34/CM-154 and CPM-154 are the same steel, and both make great knives. The CPM just gives it a little more after the HT. Same goes for D-2 vs CPM-D2. Properly made and heat treated, they both are superb. The biggest difference is often in finishing ease.
 
Anyone know if the CPM process uses graded particle sizes to fill voids between larger particles with smaller particles?
 
No. It's all heated and compressed and rolled - therefore no voids !!
 
I realize there are no voids after rolling/pressing, but do they use different size particles to minimuze porosity before pressing/rolling? Like filling a swimming pool with baskeballs and baseballs mixed together. I guess the first question should be what is the range of sizes of the partcles produced by their atomizing process. If they're all uniform in size, then what I'm asking can't be done.
 
what are you trying to do? you can get the powder to try to make your own if that is what you are looking to do. Powder metallurgy makes it possible to create supersteels that would not be possible in a traditional poured/forged/rolled ingot. With powder metallurgy you start with a spray of homogenously melted master alloy which is then atomized, each particle having the finished chemistry desired. These are effectively forgewelded into a solid without bringing the carbides nitrides etc. into solution which prevents carbide agglomeration into large blocky brittle carbides. You end up with all of the benefits, hardness, wear resistance etc without the problems of supersolvus melting

-Page
 
all the steel particales that are made in the smelt are smaller then what a cast ingot carbide size could be
and remember guys that the "forge welding /rolling" starts over 2 foot thick to get your 3/16 sheet that is then cut to bar (hows that for reduction )


that should cover any of you that think that you can forge it into something better

one day i ll make a super mosaic cpm154/3v dammy mix since for the most part if you can get the steel in cpm you can buy the powder
 
me2 said:
I realize there are no voids after rolling/pressing, but do they use different size particles to minimuze porosity before pressing/rolling?
Click to expand...

The whole point of CPM is that the particles are very close to the same size, and the smaller particles (carbides that AREN'T clumped together) are evenly distributed. I don't have the pic on this computer, but there are micrographs on the web showing the difference between (IIRC) 154CM and CPM154 that illustrate the denser, much more uniform distribution within the steel. I think that's what you're getting at, and yes it is accomplished by the CPM process.
 
Not quite what I'm getting at. I'm just curious, and the answer really is of no consequence. I guess the best way to ask is are all the particles used to make the steel essentially the same size?
 
Basic answer is yes. However more important is to get smaller size particles. I can't find it now but there is a photo on one of the European maker websites that shows thier original particle size and the latest version .They've reduced the size considerably !
 
Didnt know that they were contentiously working to get the size lower.

I did hear tho from a crucible worker that cpmD2 will not be made again(this was right after the first run) seems it ate up the gear due to not having much V in it
 
The last I heard (on some forum) was that Niagra persuaded Crucible that there is enough demand to make occasional runs of CPM D2. Basically making the stuff eats the liner of a furnace. However the liners are used up eventually anyway so they'll make a batch on special request when they have a furnace nearing the end of its liner life.

I assume that it will not be especially cheap steel.
 
Dan Pierson said:
The last I heard (on some forum) was that Niagra persuaded Crucible that there is enough demand to make occasional runs of CPM D2. Basically making the stuff eats the liner of a furnace. However the liners are used up eventually anyway so they'll make a batch on special request when they have a furnace nearing the end of its liner life.

I assume that it will not be especially cheap steel.
Click to expand...

well that woudl be the best way to do it then its like when i have a saw bnlade jsut about used up i cut any G10 that i need to and that kills it

so far as i have ever seen when you make steel CPM you might as well say it starts at 13$ a Lb then add to the cost with the mmore alloy
 
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