Internal pumps and valves for submarines
Courtesy of Stainless Steel Fasteners
Desalination plant pipework
Courtesy of Outokumpu Stainless
“6% Mo” is a generic term for several highly alloyed austenitic grades. They have been developed for highly aggressive seawater and chemical processing environments.
Approximate Composition – 20% Cr, 18-24% Ni, 6% Mo, 0.2% N plus Cu (Exact composition ranges vary between EN and ASTM standards).
This grade combines the following characteristics:
• Excellent pitting and crevice corrosion resistance (PREN > 40, comparable to superduplex
• Excellent resistance to strong acids
• Excellent stress corrosion cracking resistance
• Approved for use for structural components in swimming pools
• Higher yield strength than standard austenitic stainless steels
• Good impact toughness at sub-zero temperatures (better than superduplex)
• Improved formability compared to superduplex
• Careful control of welding parameters required
• Viable alternative to expensive nickel base alloys
Applications which illustrate these features include:
Pulp and paper, desalination, chemical processing, chemical tanker ships, heat exchangers, metal refining, flue gas desulphurisation (FGD), swimming pool structural components, offshore oil and gas, submarines, aggressive food processing e.g. soy sauce, condenser tubing.
6% Mo grades are at the top end of the stainless steel “spectrum” giving excellent service in very aggressive environments.