K390 is a steel made by Böhler Uddeholm and consists of:
Some information from the Spyderco website:
K390 steel is produced by the Böhler Uddeholm steel company, headquartered in Vienna, Austria. K390 is a powdered metallurgy, cold work tool steel with 9% vanadium and added tungsten and cobalt for excellent wear resistance and high compressive strength that is a workhorse in even the most severe applications. The carbides in the K390 mix are fine in textured and the steel’s remaining components are uniformly sized and distributed evenly throughout the matrix. This equal distribution of elements adds to the overall strength and cutting capacity when the blade is finished and sharpened.