347 Stainless Steel is a columbium and tantalum stabilized austenitic stainless steel designed to resist intergranular corrosion even after exposure to temperatures between 427°C and 899°C (800°F – 1650°F).
Due to stabilization, carbon elements form columbium-tantalum carbides instead of chromium carbides, preventing grain boundary attack. This makes 347 ideal for high-temperature applications, especially where post-weld solution annealing is not possible.

Reference standards:

• UNS S34700
• AMS 5512, AMS 5646
• ASTM A269, A276, A193
• ASME SA269, SA276
• EN 1.4550
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Chemical composition (%)

Element Content (%)
Carbon (C) 0.080 max
Manganese (Mn) 2.00 max
Silicon (Si) 0.75 max
Chromium (Cr) 17.00 – 19.00
Nickel (Ni) 9.00 – 12.00
Phosphorus (P) 0.045 max
Sulfur (S) 0.030 max
Iron (Fe) Balanced
Columbium + Tantalum (Cb+Ta) 10xC – 1.00 max
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Mechanical properties (annealed sheet and strip)

Property Value
Ultimate Tensile Strength (UTS) 515 MPa (75,000 psi)
0.2% Yield Strength 205 MPa (30,000 psi)
Elongation in 2″ ≥40%
Maximum hardness 201 HB / 92 HRB
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Physical properties

Property Value
Density 7.96 g/cm³
Melting range 1398–1446°C
Modulus of elasticity (tension) 193 GPa (28×10⁶ psi)
Thermal conductivity (20–500°C) 16.3–21.4 W/m·K
Specific heat (0–100°C) 500 J/kg·K
Electrical resistivity (20°C) 72 µΩ·in
Coefficient of thermal expansion (20–1000°C) 16.6–20.5×10⁻⁶ /°C
Magnetic permeability ≤1.02 (annealed)
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Key Features

• High resistance to intergranular corrosion.
• Excellent oxidation resistance up to approximately 900°C.
• Non-magnetic in the annealed state.
• Excellent workability and weldability without the need for post-weld annealing.
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Available forms

• Bars: Ø 0.375″ – 4.000″
• Coils: thickness 0.020″ – 0.125″
• Sheets: thickness 0.020″ – 0.125″
• Thin strips: thickness 0.0008″ – 0.015″
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Industrial applications

• Aerospace and Defense: Collector rings, aircraft engine exhausts.
• Power Generation: Boilers, cabin heaters, furnace heating elements.
• Chemical Industry: High-temperature chemical process equipment.
• Oil & Gas: Critical welding equipment without subsequent heat treatment.