A corrugated hose wall is cold-worked hard during forming, so the material has to take a great deal of deformation without cracking. That requirement, more than corrosion resistance, is why austenitic stainless dominates this industry.
Grades we work in
Two grades are held in stock. Everything else is made to order, which is normal here rather than exceptional, and it does not usually add much to the lead time.
| Grade | UNS | DIN / EN | Composition (principal) | Temperature range | What it is for |
|---|---|---|---|---|---|
| ■ AISI 304L | S30403 | 1.4307 | Cr 17.5–19.5 % · Ni 8–12 % · C ≤ 0.03 % | −196 / +450 °C | General industrial, cryogenic, excellent weldability |
| ■ AISI 316L | S31603 | 1.4404 | Cr 16.5–18.5 % · Ni 10–13 % · Mo 2–2.5 % · C ≤ 0.03 % | −196 / +450 °C | Chemical, marine, aggressive media — Mo for pitting resistance |
| AISI 321 | S32100 | 1.4541 | Cr 17–19 % · Ni 9–12 % · Ti-stabilised | −196 / +550 °C | High temperature, steam, thermal cycling above 400 °C — to order |
| AISI 904L | N08904 | 1.4539 | Cr 19–21 % · Ni 24–26 % · Mo 4–5 % · Cu 1.2–2 % | −60 / +400 °C | Ultra-corrosive service, concentrated acids — to order |
| Super duplex S32750 | S32750 | 1.4410 | Cr 24–26 % · Ni 6–8 % · Mo 3–5 % · N 0.24–0.32 % | −50 / +250 °C | Oil and gas, seawater, high-strength thin wall — to order |
| Alloy 625 (UNS N06625) | N06625 | 2.4856 | Ni ≥ 58 % · Cr 20–23 % · Mo 8–10 % · Nb 3.15–4.15 % | −196 / +980 °C | Extreme heat, aggressive chemical — to order |
| Alloy 825 (UNS N08825) | N08825 | 2.4858 | Ni 38–46 % · Cr 19.5–23.5 % · Mo 2.5–3.5 % · Cu 1.5–3 % · Ti 0.6–1.2 % | −196 / +450 °C | Reducing acids, hydrogen environments — to order |
Those are alloy service ranges. What an assembly can actually hold at temperature comes from the derating table, and on a bellows from the order-specific calculation.
Choosing by temperature
The stocked grades cover −196 °C to +450 °C. From 450 to 550 °C we derate and review the job with you. Above 550 °C it is SS 321 or Alloy 625 (UNS N06625), to order.
Choosing between them
| Grade | Choose it when | Avoid it when |
|---|---|---|
| 304L | General industrial duty, water, steam, non-corrosive media, cost matters | Chlorides present; marine or coastal; halide acids |
| 316L | Chemical, pharmaceutical, marine, food; anywhere chlorides are possible | Hydrochloric acid, wet chlorine — molybdenum does not save it |
| 321 | Sustained service above 450 °C; thermal cycling in the sensitisation range | Cost-sensitive ambient duty — you are paying for stabilisation you will not use |
| 904L | Sulphuric and phosphoric acid; higher chloride resistance than 316L | Budget-driven work — specify only where 316L is genuinely inadequate |
| Alloy 625 (UNS N06625) | High temperature with strength; aggressive chloride and acid | Where 316L or 321 would do — the cost multiple is large |
Braid material
Braid is usually SS 304, because the braid is a mechanical element rather than a wetted one and 304 has the right combination of strength and formability. Where the braid is exposed to the same aggressive atmosphere or medium as the bore — a coastal installation, a chemical bund, an assembly that gets splashed — specify 316L braid. Bronze braid is used in HVAC and marine duty; Alloy 400 (UNS N04400) braid where chlorine or saltwater contact is likely.
Documentation
Every pressure-retaining component is traceable to a mill test certificate. We issue EN 10204 3.1 certification on request, and positive material identification can be carried out on the finished assembly where the project requires it. Ask at enquiry rather than after despatch.