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Home / Products / Slip on Plate Flange / 347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength
quality 347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength factory
quality 347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength factory
quality 347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength factory
quality 347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength factory
quality 347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength factory

347 and 347H Stainless Steel Forged Slip on Plate Flanges with High-Temperature Strength

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erw carbon steel pipe

precision steel pipe

spiral steel pipe
Product Summary
347/347H stainless forged flanges are niobium-stabilized austenitic steels offering superior high-temperature strength and corrosion resistance. The 347H variant provides enhanced creep strength for demanding applications while maintaining stabilization against sensitization.

Product Details

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347 Stainless Steel Flange

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347H Stainless Steel Slip on Plate Flange

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High-Temperature Strength Forged Flange
Product Description
347 / 347H Stainless Steel Forged Flanges
347 and 347H are austenitic stainless steels stabilized with niobium (often reported as Nb + Ta). While very similar, 347H is the high-carbon version specifically designed for enhanced high-temperature strength performance.
Chemical Composition
Typical chemical composition ranges for both grades (approximate standard values):
347 Stainless Steel (UNS S34700)
Element Composition (%)
Carbon (C) ≤ 0.08%
Manganese (Mn) ≤ 2.00%
Silicon (Si) ≤ 0.75%
Phosphorus (P) ≤ 0.045%
Sulfur (S) ≤ 0.030%
Chromium (Cr) 17.0 - 19.0%
Nickel (Ni) 9.0 - 13.0%
Columbium + Tantalum (Cb + Ta) 10 × C% min, up to about 1.0% typically
Molybdenum (Mo) Usually not intentionally added (residual typically <0.75%)
Iron (Fe) Balance
347H Stainless Steel (UNS S34709)
Element Composition (%)
Carbon (C) 0.04 - 0.10% (higher than 347)
Manganese (Mn) ≤ 2.00%
Silicon (Si) ≤ 0.75%
Phosphorus (P) ≤ 0.045%
Sulfur (S) ≤ 0.030%
Chromium (Cr) 17.0 - 19.0%
Nickel (Ni) 9.0 - 13.0%
Columbium + Tantalum (Cb + Ta) 8 × C% min, typically up to around 1.0%
Molybdenum (Mo) Generally not a deliberate addition
Iron (Fe) Balance
Key Technical Characteristics
Relation to 304/321 Types
347/347H grades share similar chromium and nickel content with 304/304H, but are stabilized with niobium (instead of titanium like 321) to prevent chromium carbide precipitation and intergranular corrosion in the sensitization range (approximately 450-850°C).
Significance of "H" Grade
The "H" designation (347H) indicates higher carbon content, which provides:
  • Enhanced creep strength
  • Superior high-temperature strength performance
  • Ideal for boilers, heaters, superheaters, and refinery/chemical plant tubing applications
  • Maintained stabilization with niobium to prevent sensitization issues despite higher carbon content
Stabilization Mechanism with Niobium (Nb)
Niobium forms niobium carbides rather than allowing chromium carbides to form at grain boundaries. This mechanism:
  • Preserves chromium in solid solution
  • Maintains corrosion resistance after welding or elevated temperature service
  • Protects against intergranular corrosion
Important Note: For exact composition limits required for design, procurement, or certification purposes, always refer directly to the relevant standards (such as ASTM A240, A182, A213, A312, etc.) and the specific product's mill test certificate (MTC). Different product forms and standards may include slightly different ranges or additional controlled elements.

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