347 Stainless fasteners are used in corrosive environments where temperatures may cycle to over 800º F (425º C). Oil refinery applications are common. Other uses for 347 Stainless are in heat sensors and thermocouples.
321 Stainless (UNS S32100/ASTM A193 B8T) is a very close relative. While 347 Stainless is stabilized by the addition of columbium and tantalum to resist intergranular corrosion, 321 is stabilized by the addition of titanium.