HPNb (UNS N28701) chemical composition
Niobium-modified HP grade under ASTM A608, which covers centrifugally cast tubing for high-temperature pressure service. Nb carbides raise creep-rupture strength over standard HP; a standard choice for steam-reformer and cracker furnace tubes.
- Designation
- HPNb
- Material no.
- UNS N28701
- Standard
- ASTM A608
- Also known as
- HP40Nb, HP-Nb, ≈ 1.4852
- Family
- Heat-resistant cast steel
Chemical composition (mass %)
| Element | min | max |
|---|---|---|
| CCarbon | 0.38 | 0.45 |
| SiSilicon | 0.50 | 1.50 |
| MnManganese | 0.50 | 1.50 |
| PPhosphorus | – | 0.03 |
| SSulphur | – | 0.03 |
| CrChromium | 24.0 | 27.0 |
| NiNickel | 34.0 | 37.0 |
| MoMolybdenum | – | 0.50 |
| NbNiobium | 0.50 | 1.50 |
| FeIron | remainder | |
Basis of values: Limits per ASTM A608.
We cast HPNb
We produce heat-resistant castings by sand casting, and by centrifugal casting for cylindrical parts such as rings, bushings and sleeves. Every heat is analysed by OES; heat treatment, CNC machining in the group's Perama machine shop and EN 10204 3.1 certificates are available.
- Sand casting at our foundry in Mandra, Attica; centrifugal casting for bushings, sleeves and liners
- Heat treatment at the foundry (water, oil or air quench); CNC machining in our machine shop in Perama
- Spectrometer analysis of every heat, mechanical testing and NDT
- EN 10204 3.1 inspection certificates; ISO 9001 (both plants) and ISO 14001 (foundry) certified
Other grades in this family
For information only, without warranty: limits per the cited standard or, where stated, typical or house values; ≈ marks a comparable grade, not an equivalent. The current edition of the standard, the purchase order and the drawing govern.