Alloy 28
UNS N08028 · High-alloy austenitic Fe-Ni-Cr-Mo-Cu · Product-specific technical reference.
Alloy 28 (N08028) is included here as a material reference. Acid corrosion resistance depends on concentration, impurities and temperature.
Scope: Numerical limits below apply only to the named source, product form and condition. They are not measured results, design allowable stresses or guarantees for every product with this UNS. Acceptance follows the purchase order and applicable design/product standards.
1. Selected Chemical Requirements
Basis: ASTM A213/A213M-25, Table 2 (seamless boiler/heat-exchanger tube reference). Values are mass %. This selected-element table does not replace the complete source table and footnotes.
| Element | Requirement, mass % |
|---|---|
| C | ≤0.030 |
| Mn | ≤2.50 |
| P | ≤0.030 |
| S | ≤0.030 |
| Si | ≤1.00 |
| Cr | 26.0-28.0 |
| Ni | 30.0-34.0 |
| Mo | 3.0-4.0 |
| Cu | 0.60-1.40 |
Check required minor/combined elements, heat/product-analysis rules and footnotes in the ordered edition. An element not listed here does not imply zero content or absence of a standard requirement.
2. Mechanical Requirements and Delivery Condition
Basis: ASTM A213/A213M-25, Table 4. Published room-temperature minima. The source MPa and ksi values are shown separately; do not combine unit systems when assessing an order.
| Product / condition / size | Tensile, MPa (ksi) | 0.2% proof / yield, MPa (ksi) | Elongation, % |
|---|---|---|---|
| Specified annealed seamless tube | ≥500 (73) | ≥214 (31) | ≥40 |
A213 tube basis only; B668 or A312 orders require separate checks.
3. Designation References
UNS N08028 is the material identifier used here. Cross-system names below are comparison candidates only. EN, JIS and GB/T grades can differ in chemistry, form, condition and testing; substitution requires a technical comparison and project-required approval.
| UNS | EN / DIN | EN name | JIS | GB / ISC |
|---|---|---|---|---|
| N08028 | 1.4563 | X1NiCrMoCu31-27-4 | — | NS1404 / BG2830 (legacy) |
These are recorded designation references, not a certification of equivalence. A dash means no confirmed entry is supplied. A common UNS number or commercial name does not establish branded origin.
4. Fabrication and Service Considerations
Acid corrosion resistance depends on concentration, impurities and temperature.
Austenitic grades can suffer chloride SCC, local corrosion or sensitisation under suitable conditions. Low carbon/stabilisation reduces particular risks without eliminating every thermal-history effect. Compare suitable high-alloy austenitic, duplex and nickel candidates using representative service data.
5. Product Standards and Ordering Basis
A213/A213M covers specified seamless boiler/superheater/heat-exchanger tube; A312/A312M is a pipe specification and A269/A269M is for specified general-service tubing. Confirm that the ordered edition actually covers the UNS, route, size and condition. Alternative EN/GB/JIS delivery requires separate verification.
State grade/UNS, form, route, specification/edition, OD/wall/length, condition, examination and documents. ASME SA/SB acceptance and design-code permission require separate checks. EN 10204 type 3.1 is an inspection document, not independent product approval. Chemical and mechanical tests can use different heat/lot sampling bases.
6. Typical Applications
Wet-process phosphoric/sulphuric acid equipment after corrosion review.
These are examples, not a service-envelope approval. Confirm medium, concentration, temperature, pressure, flow/stagnation, deposits, crevices, stress and fabrication condition.
7. Product Enquiries and Related Pages
Forms, sizes, availability and certification are confirmed in the written quotation. Send an enquiry with the actual specification and service requirements.
Reference review: 30 October 2026. Editions identify the sources used; they do not assert that all named editions remain active or that alternative standards have identical requirements.