321 vs 347H Stainless Steel: Stabilized for High Heat

 

How do their stabilizing elements differ?​

321 uses titanium (5×C min) for stabilization, while 347H uses niobium (plus tantalum, 8-10×C min). 347H has higher carbon (0.04-0.10%) than 321 (0.08% max), boosting high-temperature strength.​

 

Which performs better at extreme temperatures?​

347H retains strength up to 1500°F (816°C) and has better creep resistance, making it suitable for high-pressure, high-heat settings. 321 performs well up to 1400°F (760°C) and is more stable in cyclic heat conditions.​

 

How do they compare in corrosion resistance?​

Both resist intergranular corrosion well after welding, thanks to their stabilizing elements. 321 offers slightly better resistance to general corrosion in mild environments, while 347H excels in high-heat corrosion resistance.​

 

What about their fabrication properties?​

321 is more ductile and easier to form than 347H, making it better for complex shapes. 347H requires more precise welding techniques to maintain its strength but is still workable for most industrial applications.​

 

Where are 321 and 347H commonly used?​

321 is used in aircraft exhaust systems and heat exchangers with cyclic heat. 347H finds applications in power plant boilers, pressure vessels, and high-temperature fasteners.