Spyderco byte February 2023 - EDGE-U-CATION® - K390
K390Spyderco is very proud to be the undisputed industry leader in the use of K390 tool steel in the manufacture of our knives. Manufactured by Böhler-Uddeholm, one of the world’s leading providers of tool steels, high-speed steels, and specialty materials, K390 MICROCLEAN is a state-of-the-art cold work tool steel produced by the particle metallurgy process. Its advanced alloy mix was specifically developed to provide the extreme wear resistance and high compressive strength needed in the most demanding industrial operations. Despite its toughness, K390’s exceptionally fine, homogeneous microstructure also makes it readily machinable and easy to heat treat. Collectively, these properties make K390 an outstanding blade steel.
K390 is used extensively in die cutting, stamping, fine blanking, cold forming, and plastic injection molding. It is also a preferred material for industrial cutting operations, like the knives used in the paper and cardboard industry, knives used in recycling, industrial shear blades, and similar applications. It is in many ways comparable to Crucible® Industries’ CPM®10V—an industry standard for highly wear-resistant industrial tooling—while offering improved machinability and grindability, excellent dimensional stability during heat treatment, and optimal characteristics for shaping through EDM (electrical discharge machining).
In evaluating K390, Spyderco’s battery of in-house tests confirmed that its cutting performance, strength, and edge retention easily rival some of the most advanced blade steels currently in use. Our conclusions paralleled those of Dr. Larrin Thomas, founder of KnifeSteelNerds.com, whose extensive CATRA (Cutlery Allied Trades Research Association) machine testing determined that K390’s edge retention is on par with that of well-respected powder metallurgy blade steels like ZDP-189, CPM S110V®, and CPM 10V.
From a real-world testing perspective, K390 is one of the favorite steels of acclaimed custom knifemaker Shawn Houston. Several of the videos on his incredibly popular Big Brown Bear YouTube channel demonstrate his hard-use testing of one of his preferred carry knives—a Spyderco Police™ 4 in K390. In Shawn’s words, K390 is “an M4 killer,” offering outstanding edge strength and superior edge retention, even when ground to exceptionally thin edge angles.
The exact alloy composition of K390 includes: Carbon - 2.47%, Chromium - 4.20%, Cobalt - 2.00 %, Manganese - 0.40%, Molybdenum - 3.80%, Silicon - 0.55%, Tungsten - 1.00%, and Vanadium - 9.00%. This advanced mix of alloying elements gives it a carbide volume fraction of around 17% and a high concentration of wear-resistant vanadium carbides. Because of its limited chromium content, it is a true tool steel, not a stainless steel, and should therefore be properly cared for to prevent corrosion. Compared to other tool steels, however, K390 has a tendency to patina (discolor) rather than rust. This natural process adds character over time, and, for many traditional knife users, is a very desirable characteristic in a knife carried for serious use.