Steels made from powdered elements, why?

D

DGG

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May 3, 2005
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It seems like some of the newer crucible type steels are a combination of finely powdered elements mixed together before being made into the blade.

S30V, ZDP, etc. come to mind.

Is this to speed up the manufacturing process and get lower costs? Or what?

Do the manufacturers use it so there would be no cutting of the steel involved and the blade would be sort of preprofiled in a mold and ready for final sharpening?
 
It's because you can get alloys or mixtures that you could not obtain by melting steel first then adding stuff to it. It doesn't mean that they somehow create a blade to shape, the resulting steel is still standard shape.
 
DaveH said:
It's because you can get alloys or mixtures that you could not obtain by melting steel first then adding stuff to it. It doesn't mean that they somehow create a blade to shape, the resulting steel is still standard shape.
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Thanks for the quick and informative reply.

It seems to me there is something called "scintered" steel (not sure of the spelling or the exact concept) that is made from powdered metal that can be molded into a shape and then heat treated. I think Ruger Firearms makes hand guns this way. That's what I was thinking was happening with the powdered steel used in knife making. This would be an expensive high-end manufacturing process that probably only the big boys like Spyderco would utilize.

As I understand what you are saying instead of adding stuff to a vat of molten steel and then hoping that is blends in properly, they mix all the stuff together first and then melt it down into bars, sheets, etc. Did I understand this correctly?

So you know what kind of knife steels are made from powdered metals? Can they make any type from powdered metals even tool steels?
 
This is a more expensive, higher performance process than basic smelting. It allows packing higher concentrations of alloying elements into the mix than is stable when you melt and mix the components. It also allows you to get a finer and more even distribution of the alloying elements and the iron. It gives you a refined grain structure with nicely distributed hard carbides for fine edges with high wear resistance.

You are probably thinking of an older process called something like sintering or powder fabrication where a part is shaped by packing powdered metal into a mold using heat and pressure. That gave you a fabricated part without machining. The Crucible powdered metalurgy uses a fine mix of alloy droplets and fuses them together through a briefer heating and forming process. They produce bar stock that a knife maker needs to cut and grind to a finished shape.
 
Jeff Clark has it right. As far as Ruger goes, they pioneered the use of investment casting in firearms manufacturing. They basically use the lost wax method to create a ceramic mold into which molten metal is then poured. The metal may be either a powdered version or a traditional smelt. The idea is to mold the metal to its final shape, or as close to it as possible, in order to cut down machining time and expense. I think some knives are also manufactured that way. Knives of Alaska comes to mind as an example.

I am not certain how much modern CNC machining has impacted the use of investment casting. I think Ruger still uses investment casts, and they use CNC.
 
powder metalurgy also avoids problems with differing equilibrium phases... see the diagrams under Binary Systems http://www.du.edu/~jcalvert/phys/phase.htm
some metals simply will not dissolve in others so cannot be melted together as they will simply separate again. Other mixtures form compounds that change composition as they cool because certain compositions like to solidify out first, which changes the composition of the remaining melt. mixing these as powders and sintering via flash heating and pressure allows them to mix metals and ceramics, or any number of things that won't mix in a liquid state, and allows for a uniform composition throughout the final product.
 
Kershaw Offset will have blade made using MIM. They are already doing this for multytool parts. But now it will be MIM blade out of 440C.

http://www.kinetics.com/metal/process.shtml

I am wondering how is it different them CPM steels? Does it really add value too steel or 25 micron particles is too big to make difference?

Kershaw already have SpecBump made out of CPM 154 which is CM 154 but made using powder technology.

Thanks, Vassili.
 
Carl64 said:
Any idea how the compressing part works? Shrinking it 20% is pretty big.
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Metal Injection Molding (MIM) was described to me as follows. Metal powder is injection molded and held together with a "binder". After molding the parts are put into a HIP (hot isostatic press) and heated while under extreme pressure. The binder burned out and the part is compressed to a solid.

This technology allows blade shapes that would be almost impossible to grind. It also enables the use of blade steels that are not economically feasible to produce. In other words, be prepared for some cool blade shapes made from advanced blade steels that would not be normally used!
 
nozh2002 said:
Kershaw Offset will have blade made using MIM. They are already doing this for multytool parts. But now it will be MIM blade out of 440C.

http://www.kinetics.com/metal/process.shtml

I am wondering how is it different them CPM steels? Does it really add value too steel or 25 micron particles is too big to make difference?

Kershaw already have SpecBump made out of CPM 154 which is CM 154 but made using powder technology.

Thanks, Vassili.
Click to expand...

That is what I was thinking about "Metal Injection Molding". Seems it would be an easy way to create a bunch of knives with a minimum amount of cutting, grinding, etc., although the equipment looks very expensive.

Do the manufacturers using the powdered steel use this or do they buy sheets/bars and cut and grind?

Is it used overseas to make inexpensive knives or are they just stamped out in some sort of a mold?

Look at the "Toughness" graph on this link. The powdered steel doesn't look as good as the regular stuff.

http://www.bladeforums.com/forums/showthread.php?t=366716

Here is a link that discusses the brittleness of various steels dropping knives on concrete floors from various heights. Ouch!!!
 
im reading in the damasteel handbook, one of the advantages with powdermetallurgical steels is the higher fracture strenght.

TS - martensitic stainless knife steels, carbon steels, tool steels, high speed steels. up to 4200MPa

RSP - hardenable rapidly solidified powder steels. up to over 6000MPa
 
Oh no... I hope we're not in for five years of "MIM sucks" and "MIM is OK" like you see on THR and TFL... Stop, Kershaw, before it's too late!

(BTW, MIM sucks. :) )
 
It gives a much more uniform/tighter grain, yielding better edge retention and strength.
 
DGG said:
Look at the "Toughness" graph on this link. The powdered steel doesn't look as good as the regular stuff.

http://www.bladeforums.com/forums/showthread.php?t=366716

Here is a link that discusses the brittleness of various steels dropping knives on concrete floors from various heights. Ouch!!!
Click to expand...

Well, let me shou another graph. That ZDP graph can not speak for all steel:

CPM-06.jpg


If MIM avoid grinding this mean that "hard to grind" not an issue any more for manufacturers and they may return to make really cool steels like S60V, actually to S90V which as I understand suppose to replace S60V but it is too hard to grind (may be even 10V will be available not only from custom makers!).

Cool!

Thanks, Vassili.
 
According to the graph, CPM 9V looks pretty darn good, both tough and high wear resistance. Anyone have any experience with this steel?
 
4 s ter said:
Right from the "horse's mouth" here's the explanation from Crucible

http://www.crucibleservice.com/products/CPM/index.cfm
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Thanks to everyone. What great technical information. I wonder how the knife manufacturers utilize it.

I'm always so impressed by the knowledge of my fellow BF forumites. Great links too.

As I now understand it, to make particle steel you melt everything together but before the hot molten steel mixture hardens (and the elements separate back out) you use air to blow the liquid metal into small pieces/particles that fall down some sort of tower and cool as they fall resulting in a pile of steel dust at the bottom. This is sort of like making lead shot for shotshells without the air part. Then you mush the particles under heat and pressure into larger ingots before the individual elements in each particle have time to separate out. You get a finer grain and more even mixture of elements throughout the ingot.

I wonder what would happen if they mushed the particles into a knife shape (or any shape for that matter) mold and the resolidified them using an injection molding process of some sort?
 
yuzuha said:
powder metalurgy also avoids problems with differing equilibrium phases... see the diagrams under Binary Systems http://www.du.edu/~jcalvert/phys/phase.htm
some metals simply will not dissolve in others so cannot be melted together as they will simply separate again. Other mixtures form compounds that change composition as they cool because certain compositions like to solidify out first, which changes the composition of the remaining melt. mixing these as powders and sintering via flash heating and pressure allows them to mix metals and ceramics, or any number of things that won't mix in a liquid state, and allows for a uniform composition throughout the final product.
Click to expand...

Thanks, another great link. Had to read it a couple of times though to get the gist!
 
DGG said:
I wonder what would happen if they mushed the particles into a knife shape (or any shape for that matter) mold and the resolidified them using an injection molding process of some sort?
Click to expand...

This is what Kershaw doing for Offset - MIM technology.

Other way to use powder - make layers of different powders before coocing it in to bar. Damasteel damascus is made thisway as I understand.

Thanks, Vassili.
 
Steelhed said:
According to the graph, CPM 9V looks pretty darn good, both tough and high wear resistance. Anyone have any experience with this steel?
Click to expand...
That chart doesn't take in to account ease of sharpening. It is very difficult to sharpen. Also, wear resistance doesn't always = edge retention. 3V is a much more balanced steel.
 
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