347H – High-Carbon Niobium-Stabilized Austenitic Steel: High-Temp Pressure Service Alloy

Overview

347H is a high-carbon, niobium-stabilized austenitic stainless steel, specifically designed for high-temperature, high-pressure applications requiring exceptional creep strength and intergranular corrosion resistance. As the high-carbon variant of 347, it has a carbon content of 0.04-0.10% and niobium addition (Nb + Ta: 8×C~1.10%), delivering superior high-temperature creep strength compared to 347. It retains 17.00-19.00% chromium and 9.00-13.00% nickel for corrosion resistance, is non-magnetic, and has good weldability with proper preheating. This grade is widely used in power, petrochemical, and aerospace industries for high-temperature pressure vessels and critical components.

Chemical Composition (wt%)

C: 0.04-0.10, Si ≤ 0.75, Mn ≤ 2.00, P ≤ 0.045, S ≤ 0.030, Cr: 17.00-19.00, Ni: 9.00-13.00, Nb + Ta: 8×C~1.10

Typical Mechanical Properties (Annealed Condition)

Tensile Strength (Rm): ≥ 515 MPa; Yield Strength (Rp0.2): ≥ 205 MPa; Elongation (A): ≥ 40%; Brinell Hardness (HB): ≤ 201

Core Advantages

Niobium stabilization prevents intergranular corrosion in welds and high-temperature service; high carbon content enhances high-temperature creep strength; excellent oxidation resistance (up to 850°C continuous service); non-magnetic; good weldability with preheating; superior high-temperature performance compared to 347.

Applications

High-temperature, high-pressure boilers, steam turbines, petrochemical cracking equipment, nuclear power plant components, and aerospace engine parts.

Equivalent Grades

UNS S34709, STS347H, SUS347H, EN 1.4550, GB 07Cr18Ni11Nb

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.