Stainless Steel

Stainless steels are defined as Fe-Cr-(Ni) alloys containing at least 10,5% of chromium with a maximum carbon content of 1,2%. The main function of chromium is to form a self-healing passive oxide scale on the surface that prevents chemical attack of the metal. It is the chromium element that gives steel its stainless properties. As for nickel, its content varies widely, ranging from 0 to 37% depending on the type and the grade of the steel. Indeed, adding nickel aims mainly to enhance corrosion resistance in non-oxidizing environments and to increase the stability of the microstructure at high and low temperatures.
Other alloying elements may also be added in carefully calculated quantities depending on the grade of steel. These elements include molybdenum (Mo), nitrogen (N), titanium (Ti), niobium/tantalum (Nb/Ta), copper (Cu), tungsten (W), manganese (Mn), silicon (Si), cerium (Ce), etc. Their function is to modify or stabilize the microstructure while improving the material’s properties under various service conditions (corrosive environment, heat, wear, etc.).

Base on the chemical composition, and particularly on the resulting microstructure, stainless steels are categorized into five groups, namely :

  • Ferritic (Fe-Cr) : ex. 405, 409, 430, 439, 446, etc.
  • Martensitic (Fe-Cr-C) : ex. 410, 410NiMo, CA-15, 414, 4156, 420, 440 (A, B, C)
  • Austenitic (Fe-Cr-Ni-Mo) : ex. 304, 308, 310, 316L, 318, 330, 904L, etc.
  • Duplex or Ferrito-austenitic (Fe-Cr-Ni-Mo-N-W) : ex. 329, 2101, 2304, 2205, 2507, Zeron 100
  • Precipitation Hardenable (PH) / (Fe-Cr-Ni-Cu/Nb): ex. 17-4PH (AISI 631), A-286

Nowadays, stainless steels are used in innumerable ways in the chemical industry, the food industry, the pulp and paper industry, the furniture industry, the naval industry, the automotive industry, and in Heat exchangers, storage tanks, decoration, etc.

Contact our metallurgists, to get the right alloy for your welding project.