347/347H Stainless Steel
347 is a stable austenitic chromium steel containing niobium, which can eliminate carbide precipitation, thereby preventing intergranular corrosion. Alloy 347 is stabilized by the addition of chromium and tantalum, offering higher creep and stress-rupture properties compared to alloys 304 and 304L, and is suitable for applications where sensitization and intergranular corrosion are a concern. The addition of niobium also imparts excellent corrosion resistance to alloy 347, even superior to alloy 321. 347H is a higher carbon form of alloy 347, demonstrating improved high-temperature and creep properties.
Spec: UNS S34700 / S34709
Standard:
ASTM/ASME：UNS S34700 / S34709
EURONORM：FeMi35Cr20Cu4Mo2
DIN：2.4660
Chemical Composition
Mechanical properties: (See attached image:)
Weldability
Austenitic stainless steel is considered to be the easiest to weld among all high-alloy steels.
Weldable via all熔焊 and 电阻焊 processes
Heat Treatment
The annealing temperature range is from 1800 to 2000°F.
Stress-relief annealing can be performed within the carbide precipitation range of 800 to 1500°F without any risk of subsequent intergranular corrosion; cannot be hardened through heat treatment.
Corrosion Resistance:
Offer corrosion resistance similar to alloy 304
Applications for alloys (such as Alloy 304) prone to intergranular corrosion
Commonly used for heavy-duty welding equipment that cannot be annealed and for equipment operating between 800 to 150°F (427 to 816°C).
In water and other low-temperature environments, 347 alloy is superior to 321 alloy.
Primarily used in high-temperature environments requiring desensitization to prevent low-level intergranular corrosion.
Susceptible to stress corrosion cracking
Demonstrate similar corrosion resistance to all other 18-8 Austenitic stainless steels
Application:
Alloy 347 is commonly used in the manufacture of equipment that must operate under severe corrosion conditions and is also prevalent in the oil refining industry. Typical applications that consistently employ Alloy 347 include:
High-temperature chemical process
Heat exchanger tube
High-Temperature Steam Service
High-pressure steam pipe
Radiation Overheater
Boiler Tube
Heavy-duty exhaust system
Typical Refinery Pipelines
