347
Data verified347 is the niobium-stabilised counterpart of 321, preferred for welded high-temperature service because niobium carbides are more stable during welding thermal cycles. It is a standard grade for aircraft exhausts and refinery equipment.
Chemical composition
| Element | Content (%) |
|---|---|
| C | ≤0.08 |
| Si | ≤0.75 |
| Mn | ≤2.00 |
| P | ≤0.045 |
| S | ≤0.030 |
| Cr | 17.00–19.00 |
| Ni | 9.00–13.00 |
| Nb | 10×C–1.00 |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Delivery condition | Annealed |
| Hardness | ≤217 HB (annealed) |
| Tensile strength | 515–690 MPa |
| Density | 7.90 g/cm³ |
Heat treatment
Solution anneal 980–1120 °C, rapid cool; niobium stabilisation is effective without a separate stabilising anneal.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 1.4550 |
| aisi | 347 |
| jis | SUS347 |
| gb | 06Cr18Ni11Nb |
Compare side by side: 347 vs 347H · 347 vs 321
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Aircraft exhaust systems, high-temperature chemical plant, welded heavy-wall vessels, expansion bellows.
Processing: Good weldability; the stabilised chemistry keeps weld zones resistant to intergranular corrosion in the 425–870 °C service range.
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Ask for a quotationVisit NasteelSource: ASTM A240 / EN 10088 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.