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What is Powder Metallurgy Steel in Knives?

What is Powder Metallurgy Steel in Knives?

by Larry Connelley

If you ever went shopping for a quality knife, you no doubt heard a number of cutlery-specific terms bandied about by those in the the know. A couple of those terms you may have heard are "powder steel" and "particle steel". Do you know what they mean?

Particle steel and powder steel are virtually the same thing. Powder, or particle, steel is the 21st century evolution of modern steel making for specialty steels that are designed to endure extreme performance.

Advantages of Powder Metallurgy in Knives:

The advantage of this specialty steel manufacturing process provides a blade that has increased wear resistance, cleaner finishes, improved grindability and greater toughness that allows for less chipping. The Particle Metal process can allow a knifemaker to heat treat to a higher level with less fear of failure. The greatest advantage of PMS is that higher alloy grades can be achieved as opposed to more conventional steel manufacturing and the particles are more evenly distributed in the alloy of the steel. The Powder Metallurgy Steel process costs more to create steel but gives the user significant functional advantages.

The technical name for the the steel is powder-metallurgical steel, or PMS for short. PMS allows for much more even homogenous distribution of elements in the steel alloy. Crucible Industries, a large American manufacturer of high-end knife steel, calls their proprietary PMS process Crucible Particle Metallurgy or CPM. The CPM process was developed in 1970.

It is important to have an evenly mixed alloy so that the steel doesn't have any weak spots and the character of the alloy mixture is even throughout the material. With particle steel, blades can perform at their peak performance with much less fear of material failure. This is important in knives or other extreme uses like jet engines turbines, high speed manufacturing or other specialty manufacturing processes.

The PMS Process:

Particle steel manufacturing process is complicated and fascinating. Once the correct amounts of elements are in the steel alloy, the super-heated liquefied steel is ejected through a narrow nozzle and then rapidly cooled, resulting in a perfectly uniform powder. Each particle of steel has the same amount of each element - uniform distribution even at a particle level. In normal steel production, as steel cools the elements are not as evenly distributed. This particularly affects the carbides in the steel with an uneven distribution.

This powder steel is heated to forge temperatures and formed into ingots while under extreme and isostatic pressure (pressure from all sides). Known as "hot isostatic pressing" or HIP, this reassembles the particles via sintering into a single billet of steel - carrying the equal distribution of the particle into a workable bar of steel.

Particle steel in knives can be stainless or not, depending on how much chrome is present in the alloy. If there is 11-12 percent or more chrome in the alloy, the knife blade is considered stainless. The more chrome in the alloy, the more stainless the steel is.