Stainless steel 347 is similar to 321 stainless in that it is often used as a stable replacement for Type 304. However, in the case of 347, the stabilizer is columbium. This metal enhances the ability to withstand intergranular corrosion already present in 347 for maximum performance. Additionally, columbium allows 347 to be heated repeatedly at temperatures up to 1650°F. Therefore, the metal is commonly used in high temperature equipment such as gaskets and expansion joints, as well as in rocket engines and chemical manufacturing.
|Steel Grade||300 Series, 347H||Type||Seamless, Round Pipe/Tube|
|Standard||ASTM, AISI, GB, DIN, JIS||Certification||ISO, SGS, BV, ISO/CE/SGS|
|Technique||Cold Rolled, Cold Drawn||Min./Avg.||Min./Avg.|
|Outer Diameter||3.2-127mm, Customized||Finish||Brush Polish Cold Drawn, Pickled, Bright Annealed|
Alloy 347 is a stabilized austenitic chromium steel containing columbium to eliminate carbide precipitation, thereby eliminating intergranular corrosion. Alloy 347 is stabilized by the addition of chromium and tantalum and provides higher creep and stress rupture properties than alloys 304 and 304L, which can also be used for exposures of concern to sensitization and intergranular corrosion. The addition of columbium also gives Alloy 347 excellent corrosion resistance, even better than Alloy 321. 347H is a higher carbon content form of Alloy 347 and exhibits improved high temperature and creep properties.
Specifications: UNS S34700 / S34709
Alloy 347 is frequently used in the manufacture of equipment that must be put into service under severe corrosive conditions and is also common in the petroleum refining industry. Applications where Alloy 347 has been used consistently include:
High temperature chemical process
heat exchanger tube
High temperature steam service
High pressure steam pipe
heavy duty exhaust system
General Refinery Pipelines