Stainless steel duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications. Duplex grades are characterized into groups based on their alloy content and corrosion resistance. Precipitation hardening stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than the other martensitic grades. The most common, 17-4PH, uses about 17% chromium and 4% nickel. The designation "CRES" is used in various industries to refer to corrosion-resistant steel. Most mentions of CRES refer to stainless steel, although the correspondence is not absolute, because
Stainless steel about 0.4%) are mostly used for cutting tools: Cutlery, Razor blade steel, Blender blades, etc. Replacing some of the Carbon in martensitic stainless steels by Nitrogen is a fairly recent development. The limited solubility of Nitrogen has been increased by the PESR process (Pressure Electroslag Refining) in which melting is carried out under a high nitrogen pressure. Up to 0.4% N contents have been achieved leading to higher hardness/strength and higher corrosion resistance. As the PESR is expensive, lower but significant N contents have been achieved using the standard AOD process. They are magnetic. They are not as corrosion resistant