Grade 347 Austenitic Stainless Steel – Niobium-Stabilized Corrosion-Resistant Alloy

Description

Grade 347 is a niobium (columbium)-stabilized austenitic stainless steel, designed to provide superior intergranular corrosion resistance and high-temperature stability. Similar to 321, it is based on the 18-8 composition (17.0-19.0% Cr, 9.0-13.0% Ni), but uses niobium (0.80-1.20%) instead of titanium for stabilization. Niobium binds with carbon more effectively than titanium, offering enhanced resistance to intergranular corrosion at higher temperatures (up to 850°C) and better weldability. Unlike 321, 347 offers superior creep strength and stability in long-term high-temperature service, making it suitable for critical applications in aerospace, nuclear, and petrochemical industries. It remains non-magnetic at room temperature, has good formability, and is ideal for welded components requiring long-term corrosion and high-temperature performance.

Chemical Composition (wt%)

C ≤ 0.08, Cr: 17.00-19.00, Ni: 9.00-13.00, Nb+Ta: 0.80-1.20, Mn ≤ 2.00, Si ≤ 1.00, P ≤ 0.045, S ≤ 0.030

Mechanical Properties

Tensile Strength ≥ 515 MPa, Yield Strength ≥ 205 MPa, Elongation ≥ 40%, Hardness ≤ 201 HB

Advantages

Niobium-stabilized for superior intergranular corrosion resistance; better high-temperature stability than 321; excellent weldability; non-magnetic; good creep strength; suitable for critical high-heat applications.

Applications

Aerospace components, nuclear reactor parts, petrochemical piping, heat exchangers, boiler parts, and critical high-temperature welded structures.

Equivalent Grades

AISI 347, UNS S34700, EN 1.4550, GB 06Cr18Ni11Nb

 

Stainless Steel Suppliers

If you have project requirements for stainless steel, we welcome your order. GNEE has a large inventory of popular products for you to choose from. It can be processed into various practical product forms, including plates, coils, tubes, bars, wires, etc. For detailed chemical composition information and free samples, please contact our factory immediately. We offer competitive prices and excellent service.Email: info@gneestainless.com

 

Testing and Documentation: Factory test certificate, EN 10204 3.1, chemical report, mechanical report, destructive testing report, non-destructive testing report, PMI test report, visual inspection report, third-party inspection report, NABL certified laboratory report.
Packaging: Wooden crate packaging, bubble wrap packaging, steel strapping, or packaging according to customer requirements.