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Elements (Max.) C Mn P S Si Cr Ni Cb+Ta Ta Co .08 2.00 .045 .03 .75 17/19 9/13 10xC Min. - -
Type 347 is a chromium-nickel stainless steel modified by the addition of columbium and.tantalum to overcome the dangers of intergranular corrosion common to other austenitic stainless steels during or after exposure to temperatures of 800 to 1500 Deg. F. It is non-magnetic in the annealed condition and not hardenable by heat treatment.
Applications: Used for heavy welded assemblies which cannot be annealed after welding. Also used where operating conditions cause exposure within the temperature range between 800 and 15O0 Deg. F and where corrosive conditions are severe, such as aircraft exhaust stacks, manifolds and ring collectors. It is used to advantage in combating corrosion cracking resulting from stress in corrosive media due to vibration or other causes.
Corrosion Resistance: Type 347 is resistant to intergranular corrosion. It has about the same general corrosion resistance as Type 304.
Resistance To Scaling: Excellent scale resistance at temperatures up to 1650 Deg. F in continuous service.
Machinability: Type 347 has a machinability rating of approximately 36%, with B-1112 rated 100%. Surface cutting speed on automatic screw machines is approximately 60 feet per minute.
Weldability: Easily welded by all the commercial processes except forge or hammer welding.
Forming: This grade has good drawing and stamping properties.
Forging: Forge between 2100 and 2300 Deg. F Do notforge below 1800 Deg. F
Annealing: Annealing range is between 1850 and 2050 Deg. F Cool rapidly. Water should be used for heavier sections, air for lighter sections. The stress relieving range is between 400 and 750 Deg. F