Powdered steel question

Y

Yogi619

Joined
Dec 4, 2012
Messages
20
Hey everyone,

I recently made a post where I'm lookig for a knife that will probably get alot of heavier duty use (read, I'll probably abuse it), and alot of guys gave me some great suggestions.

I'm trying to educate myself more on different kinds of steels, and one of the trends that I'm seeing is that the powdered steels from Crucible (CPM steels) seem to be pretty desirable, at least when it comes to folders. Please correct me if I'm wrong, but the process to make these steels looks to be the same as the MIM parts used in guns.

I was wondering why these steels are big sellers (and expensive) on knives, but considered inferior parts on gun when compared to forged? Also, is there such thing as a forged knife steel outside of kitchen knives?
 
No, powdered steels are different from MIM. The steel powder is sintered into billets then rolled out just like ingot steel. This rolling is a form of forging.

MIM is used to mold net shapes, which saves a lot of machining/grinding time. Powdered steels have to be cut and ground the same as regular ingot steel. The reasons for PM (powder metallurgy) include: 1) smaller grain size for greater ductility and ability to hold a fine edge, 2) the ability to cram in more alloying elements without them segregating upon freezing.

Bill
 
Last edited:
There is a HUGE difference in the materials used in guns and in knife blades.

Like comparing the space shuttle to a paper airplane.
 
Knife steels in general are forged. Whether that's by a blacksmith with a hammer and some bar stock or by a factory like Crucible and some elemental particles.

The neat thing about particle steel is that the alloys are as near to homogenous as we can get these days. I've heard that evening out (homogenizing) the molecules in the alloy was the goal of the old Japanese folding technique. We can now do it much more effectively. Not only are the CPM steels made better, they are high-tech, purpose-built alloys.

More info:
http://www.crucibleservice.com/eselector/general/generalpart3.html
 
Thanks for the link. Please tell me if I have this straight...

Standard steel making is done by melting different metal types together into an alloy, then poured into an ingot mold. Particle steel uses the same melting process, yet instead of pouring it into a mold, compressed gas blows the melted steel onto another surface, where it is then collected and put into a steel jar. The powder is then pressed together into a solid blank. Is that about the gist of it?

I'm seeing 154Cm, and CPM154 which I'm assuming are the same alloy, but each utilize these two different processes. What is typically the price difference on these two steels? Or am I completely off still?
 
CPM154 is similar in properties and price to S30V. 154CM is cheaper. Check out alphaknife or some other supplier for details.
 
CRKT, I should have phrased my question about pricing better. If two knives were offered in the same style by the same manufacturer,with the only exception being the steel used, 154Cm vs CPM154 in this example, what would I expect the price difference to be? When I look at a knife dealers website, I see the two different steels used by different makers, and it makes it hard to judge the price difference when there isn't a control.
 
It's looking like the price difference between these two alloys is minimally $100.

If Crucible does a run of say 1,000 knife blanks, and charges a $100 difference between these two alloys, that means there's a $100,000 difference in their gross profit.

Does the difference in these manufacturing techniques cost $100,000 per 1,000 knife blanks, or is this just an example of one being better than the other, and Crucible and other knife steel companies are charging a premium for them, because "better always costs more"?

I'm sorry if these questions have been asked before, or if I'm completely missing something, but these numbers seem somewhat staggering, especially after reading the differences in how they're made via the Crucible link.

Ankerson, it looks like you're somewhat of the steel expert around here, and I would be grateful if you could give me a better run down of this process.
 
Hi Yogi,
Once Crucible makes the powder they put it in a large can. The can is heated and dropped into a chamber where it is subjected to extremely high pressure. The result is a large diameter solid round that needs to be rolled into a slab at Crucible. We buy the slab and hot roll it into sheet for knife makers and several other industries. The reason for the high cost is the extra step of turning the powder into a solid round and the relatively small quantities per heat. An air melt heat is about 55,000 pounds and a CPM heat is about 5,000 pounds. Crucible itself does not make any knife blanks.

I hope this helps a little,
Bob
 
Niagara Specialty Metals would be a good place to have a look at prices.

You may want to look up a few ways of making steel to better understand the how and why of particle metallurgy. PM prevents carbide stringing and increases impact toughness. Grain size is controlled in the heat treat. Wear resistance will be roughly the same as long as the alloy content is the same, such as your examples of 154CM and CPM154.

MIM differs in that it introduces a binder into the powder, and poor QC in the molding can leave voids where the binder cooks off that sintering does not fix.

http://en.wikipedia.org/wiki/History_of_ferrous_metallurgy#Industrial_steelmaking
http://en.wikipedia.org/wiki/Electric_arc_furnace
http://en.wikipedia.org/wiki/Vacuum_induction_melting
http://en.wikipedia.org/wiki/Vacuum_arc_remelting
http://en.wikipedia.org/wiki/Powder_metallurgy
http://en.wikipedia.org/wiki/Hot_isostatic_pressing
 
Bill1170 said:
No, powdered steels are different from MIM. The steel powder is sintered into billets then rolled out just like ingot steel. This rolling is a form of forging.

MIM is used to mold net shapes, which saves a lot of machining/grinding time. Powdered steels have to be cut and ground the same as regular ingot steel. The reasons for PM (powder metallurgy) include: 1) smaller grain size for greater ductility and ability to hold a fine edge, 2) the ability to cram in more alloying elements without them segregating upon freezing.



Bill
Click to expand...
I havent seen any information about the grain size being finer for cpm/powder steels. There is a lot about the carbides being finer. Do you have a source for grain size data?
 
Too many people confuse carbide size and grain size !! CPM produces fine carbide size [more uniform structure too] .

Crktm -there are no molecules in metal !

There has been an unfortunate semantic problem here which is confusing.
PM [powder metal ] originally was the process of compressing metal powder in a precision die ,then sintering it [heating] to bond ,by diffusion, the particles .That process can be varied to produce filters to producing close to 100% density parts . HT, carburizing ,etc can be done to these parts.
MIM is an outgrowth of PM .A mix of metal powder and a polymer [wax] is injected into a mold , the part is then heated to melt out the wax then heated higher to bond the powder like PM.
Crucible called their process Particle Metallurgy preventing confusion. However people called it powder metal ,especially the Europeans. That seems to becoming more common .
PM and MIM are then related and companies such as Remington Arms have been using PM from about 1970 and later added MIM for their own and other gun companies. I had seen their original PM process.
As nsm explains particle metallurgy is a different process and ends up with wrought material. The European methods also end up as wrought material.
Uniform microstructure , fine carbides ,isotropic properties are some of the benefits of the CPM process ,which BTW havs been around since about 1970 !
I've known it all along !! When in doubt ask a metallurgist --he'll get you confused ! LOL,LOL
 
Good info! I think that pretty much answers my question. In a nutshell, MIM is a similar method used to cast finished parts, whereas PM is usually heated/pressed into a billet, and then sent for the end user to make what he pleases with it. Knives in this case.
 
You must log in or register to reply here.
Back
Top