The new strength-toughen mechanisms, such as super fine Martensitic laths, new strength phases, Laves phase and M₂C carbide, precipitated coherence with Martensitic matrix and the VIM + VAR double vacuum melting with super pureness, super homogenization hotwork, controlled Martensite transformation heat treatment techniques have been investigated. By means of them a new type of low carbon stainless steel, 14Cr-12Co-5Mo-Me, with ultra-high strength, high plasticity and high toughness was obtained.