A martensitic stainless steel. It's composed of these major alloy elements (I don't list the minor elements since they don't play a major role) : Carbon: 0.95-1.25% This increases hardenability and wear resistance, but decreases toughness in higher amounts.Manganese: .45% This is added to reduce brittleness and improve forgeability, hardenability, and reducing deformation.Silicon: .30% This is a deoxidizer and improves hot-forming properties.Chromium: 17.00-18.00% Added only to high alloy tool steels, this improves hardenability, high wear resistance, toughness, and corrosion resistance.