Introduction To Austenitic Stainless Steel Casting Parts

Austenitic stainless steel can be divided into four groups: Cr-Ni series; Cr-Ni-Mo, Cr-Ni-Cu, or Cr-Ni-Mo-Cu series; Cr-Mn-N series; and Cr-Ni-Mn-N series. The Cr-Ni series is represented by "18-8". The Cr-Ni-Mo, Cr-Ni-Cu, and Cr-Ni-Mo-Cu series add 2%-3% molybdenum and copper (or both) to improve resistance to sulfuric acid corrosion. However, molybdenum is a ferrite-forming element, so to ensure the formation of austenite, the nickel content needs to be appropriately increased after adding molybdenum. The Cr-Mn-N series is an alloy that saves nickel. When the chromium content is greater than 15%, adding manganese alone cannot achieve the desired austenitic structure. It is necessary to add 0.2%-0.3% nitrogen to obtain a single austenite. To obtain a single austenite, more than 0.35% nitrogen must be added. However, excessive nitrogen content often leads to defects such as porosity and looseness in castings. By adding an appropriate amount of nitrogen and a small amount of nickel, a single austenite can be obtained, resulting in the Cr-Ni-Mn-N series. Of course, to obtain an austenite-ferrite duplex structure, it is not necessary to add more nitrogen and nickel.