Below is a brief explanation of conventional versus CPM steel. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
Conventional Steelmaking vs.Particle Metallurgy Processing
Conventional steelmaking begins by melting the steel in a large electric arc furnace. It is usually followed by a secondary refining process such as Argon Oxygen Decarburization (AOD). After refining, the molten metal is poured from the furnace into a ladle, and then teemed into ingot molds.
Although the steel is very homogeneous in the molten state, as it slowly solidifies in the molds, the alloying elements segregate resulting in a non-uniform as-cast microstructure. In high speed steels and high carbon tool steels, carbides precipitate from the melt and grow to form a coarse intergranular network. Subsequent mill processing is required to break up and refine the microstructure, but the segregation effects are never fully eliminated. The higher the alloy content and the higher the carbon content, the more detrimental are the effects of the segregation on the resultant mechanical properties of the finished steel product.
The CPM process also begins with a homogeneous molten bath similar to conventional melting. Instead of being teemed into ingot molds, the molten metal is poured through a small nozzle where high pressure gas bursts the liquid stream into a spray of tiny spherical droplets. These rapidly solidify and collect as powder particles in the bottom of the atomization tower. The powder is relatively spherical in shape and uniform in composition as each particle is essentially a micro-ingot which has solidified so rapidly that segregation has been suppressed. The carbides which precipitate during solidification are extremely fine due to the rapid cooling and the small size of the powder particles. The fine carbide size of CPM steel endures throughout mill processing and remains fine in the finished bar.
The powder is screened and loaded into steel containers which are then evacuated and sealed. The sealed containers are hot isostatically pressed (HIP) at temperatures approximately the same as those used for forging. The extremely high pressure used in HIP consolidates the powder by bonding the individual particles into a fully dense compact. The resultant microstructure is homogeneous and fine grained and, in the high carbon grades, exhibits a uniform distribution of tiny carbides. Although CPM steels can be used in the as-HIP condition, the compacts normally undergo the same standard mill processing used for conventionally melted ingots, resulting in improved toughness.
EXCELLENT post KS. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />
I still feel (and I could be wrong) that the final heat-treatment can be and is likely a significant factor in how non-CPM steels can compare to CPM steels.
All things being equal, everything I have read indicates CPM steels are consistant improvements over Non-CPM steels.
D2 (as mentioned) is a prime example.
Non-CPM D2 has historically been all over the board in quality.
Sometimes it is super tough, but a bugger to get sharp.
Sometimes it is VERY brittle and gets and holds an awesome edge... till it micro-fractures or breaks.
Sometimes it is a bugger to sharpen and holds and edge for a LONG time.
Busse used regular old D2 on the Swamp Rat Bog Dog and Rat Skinner and was able to make the D2 VERY tough for stainless steel and still get it to RAZOR sharp and hold it's edges. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" /> <img src="/ubbthreads/images/graemlins/bowdown.gif" alt="" />
A lot of people SWEAR by Dozier's D2 blades. I hear they sharpen pretty well and hold AWESOME edges. I have never owned a Dozier. But, I have seen a couple of examples where even the Great Bob Dozier D2 knives have snapped - implying somewhat brittle. I am not bashing Bob Dozier knives. His knives are typically for skinning and chore use and should be GREAT for what they are intended to do. But, it "Seems" Busse's heat treatment of D2 gives Busses D2 a better compromise of toughness along with the edge qualities - providing MORE variety in use and MORE comfort/faith in use.
However, I have seen CPM-D2 on Spyderco and some other makers get HUGE raves and reviews. There seems to be MUCH better consistancy in performance, edge qualities, toughness, etc. with CPM-D2 over regular D2..... although, I doubt most Spyderco's and most of the knives I have seen CPM-D2 used on get abused much. So, I am not sure about how tough they really are. But, I will put stock in what I have read for edge qualities, ability to sharpen, cut like crazy, hold their edges, and such.
Similarly, I feel there is a LOT of reason to believe that most makers are going to have better consitancy in performance with CPM-154 over regular 154CM.
But, considering how well I have seen regular D2 perform that was heat-treated by Busse compared to CPM-D2, to me, I have reason to believe Busse can "probably" do similar with 154CM.
I still don't know a ligitimate way to compare Busse 154CM vs. another makers CPM154 other than to torture test them.
Similarly, I have NOT seen a comparison test of Busse's D2 vs. other makers CPM-D2... But, I would be curious! <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />
I am not interested in trashing my knives for that. But, I don't mind watching others do it. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />
Still, I have reason to believe Busse could "probably" provide EVEN better results with their own heat treatment (all things being equal) of CPM-154 over regular 154CM.
But, I don't know that I would say that "neccessarily" makes as a whole CPM-154 better than Busse 154CM (??????) <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />
"Still", I don't expect to see any changes soon in what Busse is using. They seem to have inventory of 154CM, have worked on perfecting heat-treatment for 154CM and have results they are happy with. I expect they will use regular 154CM for a while. And I don't have "much" reason to have issue with that. For knives at 5" and under, Busse's 154CM seems pretty darn tough and can get VERY sharp.
My ONLY issue is it is pretty hard to sharpen.
For some knives, I might prefer more toughness. But, I still say 154CM can be PLENTY tough for many applications. It really just comes down to each person knowing how they are using their knives. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />
I wouldn't expect Busse's 154CM to be the best choice for cutting door hinges off a Jeep. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" /> But, it will do most skinning and wood-crafting chores very well and without rust. <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" /> - Some people desire stainless. And I can appreciate why in some cases. So, if stainless is desired, Busse's 154CM or D2 are both going to be pretty high on the toughness level "FOR Stainless"!!! <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />
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