347 vs 347H Austenitic Stainless Steels: Stabilized vs High-Carbon High-Temp Grades

 

What are their core compositions and key performance differences?

347 contains 17–19% Cr, 9–13% Ni, 0.7–1.0% Nb, ≤0.08% C-stable up to 800°C (industrial furnace parts).347H features the same Cr/Ni/Nb content, plus 0.04–0.10% C-niobium carbides boost creep resistance up to 900°C (nuclear steam lines).

How do their high-temperature capabilities suit distinct applications?

347 is used for boiler tubes, exhaust headers (≤800°C service).347H dominates gas turbine combustion chambers, nuclear power plant core supports (≥800°C service).

In which scenarios is one grade irreplaceable?

Choose 347 for cost-sensitive high-heat welded parts (≤800°C).Opt for 347H for ≥800°C high-pressure service-347's low carbon reduces creep resistance.

What are the cost and fabrication trade-offs?

347H costs 5–8% more than 347 (tight carbon control), so it's only used for extreme high-temp needs.Both weld well with 347 filler metals, but 347H requires stricter heat input control.

What are the key guidelines?

Neither grade suits marine environments-use 316Ti for corrosion + heat resistance.Prioritize 347 for ≤800°C welded parts; select 347H for ≥800°C ultra-high-temp service.