- Cold Roll
- Hot Roll
- Other Metals
Types 321 (S32100) and 347 (S34700) are stabilized stainless steels which offer as their main advantage an excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range from 800 to 1500°F (427 to 816°C). Type 321 is stabilized against chromium carbide formation by the addition of titanium. Type 347 is stabilized by the addition of columbium and tantalum.
While Types 321 and 347 continue to be employed for prolonged service in the 800 to 1500°F (427 to 816°C) temperature range, Type 304L has supplanted these stabilized grades for applications involving only welding or short time heating.
Types 321 and 347 stainless steels are also advantageous for high temperature service because of their good mechanical properties. Types 321 and 347 stainless steels offer higher creep and stress rupture properties than Type 304 and, particularly, Type 304L which might also be considered for exposures where sensitization and intergranular corrosion are concerns. This results in higher elevated temperature allowable stresses for these stabilized alloys for ASME Boiler and Pressure Vessel Code applications.
The Types 321 and 347 alloys have maximum use temperatures of 1500°F (816°C) for code applications like Type 304, whereas T304L is limited to 800°F (426°C). Applications for Types 321 and 347 include those for welded construction and parts subjected to heating in the carbide precipitation range, aircraft collector rings, aircraft exhaust stacks, boiler casings, cabin heaters, carburetor air intensifier tubes, exhaust manifolds, fasteners, fire walls, flash boilers, flexible couplings, furnace heating elements, jet engine parts, large mufflers for stationary diesel engines, pressure vessels, stack liners, all-welded tank car for carrying chemicals, annealing box inner covers, collector rings, expansion joints, heat resistors, heavy wall welded equipment, welded tanks for storing organic chemicals, wire cloth and screens (industrial).
RESISTANCE TO CORROSION
Types 321 and 347 alloys offer similar resistance to general, overall corrosion as the unstabilized chromium nickel Type 304. Heating for long periods of time in the chromium carbide precipitation range may affect the general resistance of Types 321 and 347 in severe corrosive media.
Refer to our "Guide to STAINLESS" for grades, shapes and various properties.