347/347H Stainless Steel

347/347H stainless steel is similar to 321 albeit stabilised by the addition of Columbium and Tantalum. This offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range 427-816 Degrees C.

Alloy 347 is a stabilized, austenitic, chromium steel containing columbium which allows for the elimination of carbide precipitation, and, consequently, intergranualr corrosion.

Alloy 347 is stabilized by the additions of chromium and tantalum and offers higher creep and stress rupture properties than alloy 304 and 304L which may also be used for exposures where sensitization and intergranualr corrosion are of concern. The addition of columbium also allows Alloy 347 to have excellent corrosion resistance, even superior to that of alloy 321.

347H is the higher carbon composition form of Alloy 347 and demonstrates improved high temperature and creep properties.

Specifications: UNS S34700 / S34709

应用程序:

Alloy 347 is frequently used for the fabrication of equipment, which must be placed in service under severe corrosive conditions, and is also common to the petroleum refining industries. Applications that consistently used Alloy 347 include:

• High temperature chemical processes
• Heat exchanger tubes
  
• High temperature steam service
  
• High pressure steam pipes
  
• Radiant superheaters
  
• Boiler tubes
  
• Heavy duty exhaust systems
  
• General refinery piping
  

Standards:

• ASTM/ASME: UNS S34700 / S34709
• EURONORM: FeMi35Cr20Cu4Mo2
  
• DIN: 2.4660

Processing:

Weldability

• Austenitic stainless steels are considered to be the most weldable out of all high alloy steels
• Can be welded by all fusion and resistance welding processes

Heat Treatment

• Annealing temperature range is 1800 to 2000°F
• May be stress relief annealed within the carbide precipitation range of 800 to 1500°F without any danger of subsequent intergranualr corrosion
• Cannot be hardened by heat treatment

Chemical Properties:

Grade	C	Cr	Mn	Ni	P	S	Si	Cb/Ta
347	0.08 max	min: 17.0 max: 20.0	2.0 max	min: 9.0 max: 13.0	0.04 max	0.30 max	0.75 max	min:10x C max: 1.0
347H	min: 0.04 max: 0.10	min: 17.0 max: 20.0	2.0 max	min: 9.0 max: 13.0	0.03 max	0.30 max	0.75 max	min:10x C max: 1.0

Mechanical Properties:

Grade	Tensile Strength ksi (MPa)min	Yield Strength 0.2% ksi offset ksi (MPa) min	Elongation (% in 50mm) min	Hardness (Brinell) MAX	Hardness (Rockwell B) MAX
347/347H	75 (515)	30 (205)	40	201	95

Physical Properties:

Density lbm/in3	Coefficient of Thermal Expansion (min/in)-°F		Thermal Conductivity BTU/hr-ft-°F	Specific Heat BTU/lbm -°F	Modules of Elasticity (annealed)2-psi
at 68 °F	at 68 – 212°F	at 68 – 1832°F	68-932°F	at 32 – 212°F	在张力(E)
0.288	9.2	11.4	14.7	0.12	28 x 106