ASTM B564 Hastelloy C-276 (UNS N10276) • C-22 (UNS N06022) • C-4 • C-2000 • B-2 (UNS N10665) • B-3 (UNS N10675) • Hastelloy X (UNS N06002) • All Types and Pressure Classes
BROWSE BY MATERIAL
Hastelloy is the registered trade name for a family of nickel-based superalloys from Haynes International, engineered specifically for the most aggressive corrosive environments in chemical processing, oil refining, pharmaceuticals, and high-temperature industrial applications. Unlike stainless steels that are rendered useless by hot mineral acids, Hastelloy alloys maintain near-zero corrosion rates in environments including hot concentrated hydrochloric acid (HCl), sulfuric acid (H₂SO₄), phosphoric acid, wet chlorine, and mixed-acid streams that would rapidly destroy even Inconel 625.
Tesco Steel & Engineering manufactures Hastelloy flanges across the full C-series and B-series grade range — from the universally corrosion-resistant C-276 to the reducing-acid specialist B-3, and the high-temperature Hastelloy X — all supplied to ASTM B564 with full material traceability including Positive Material Identification (PMI), which is critical given the visual similarity between Hastelloy grades. All flanges are available with EN 10204 3.1 or 3.2 mill test reports, third-party inspection, and NACE MR0175 compliance documentation.
⚠ Critical Grade Selection Rule — C-Series vs B-Series
Hastelloy B-2 and B-3 are Ni-Mo alloys with NO chromium. They offer unrivalled resistance to pure HCl and reducing H₂SO₄ — but will corrode rapidly in any oxidising environment, including streams with dissolved oxygen, ferric ions (FeCl₃), cupric ions, or oxidising acids. If your process contains or can become oxidising, always specify a C-series grade (C-276 or C-22). Specifying B-series in the wrong environment is a common and costly engineering error.
Oxidising + reducing service — the most versatile Hastelloy grades
Thermally stable and broadest multi-acid capability
For pure HCl and reducing H₂SO₄ ONLY — not for oxidising media
Gas turbines, combustors, industrial furnaces — up to 1200°C
| Grade | UNS | Ni | Cr | Mo | Fe | W | Cu | Co (max) |
|---|---|---|---|---|---|---|---|---|
| C-276 | N10276 | bal. | 14.5–16.5 | 15.0–17.0 | 4.0–7.0 | 3.0–4.5 | — | 2.5 |
| C-22 | N06022 | bal. | 20.0–22.5 | 12.5–14.5 | 2.0–6.0 | 2.5–3.5 | — | 2.5 |
| C-4 | N06455 | bal. | 14.0–18.0 | 14.0–17.0 | max 3.0 | — | — | 2.0 |
| C-2000 | N06200 | bal. | 22.0–24.0 | 15.0–17.0 | max 3.0 | — | 1.3–1.9 | 2.0 |
| B-2 | N10665 | bal. | max 1.0 | 26.0–30.0 | max 2.0 | — | — | 1.0 |
| B-3 | N10675 | bal. | max 1.5 | 27.0–32.0 | 1.0–3.0 | max 3.0 | — | 3.0 |
| Hastelloy X | N06002 | bal. | 20.5–23.0 | 8.0–10.0 | 17.0–20.0 | 0.2–1.0 | — | 0.5–2.5 |
HOT HCl (REDUCING) — Relative corrosion resistance (higher = better)
OXIDISING ACIDS (HNO₃, wet chlorine) — Relative corrosion resistance
Guidance only — always confirm by immersion testing or published corrosion data for specific acid concentration, temperature, and impurities.
| Parameter | C-276 | C-22 | B-2 / B-3 | Hastelloy X |
|---|---|---|---|---|
| AWS Filler Wire | ERNiCrMo-4 | ERNiCrMo-10 | ERNiMo-7 (B-2) / ERNiMo-10 (B-3) | ERNiCrMo-2 |
| AWS Electrode | ENiCrMo-4 | ENiCrMo-10 | ENiMo-7 | ENiCrMo-2 |
| Process | GTAW, SMAW, GMAW | GTAW, SMAW | GTAW preferred | GTAW, SMAW |
| Preheat | Not required | Not required | Not required | Not required |
| Max Interpass | 175°C | 175°C | 150°C | 175°C |
| PWHT | Not required | Not required | Solution anneal optional for severe HCl (B-2); B-3 generally not needed | Not required |
| ASME P-Number | P44 | P44 | P44 | P45 |
| ASME/ANSI B16.5 | WN, SO, SW, BL, TH, LJ, RTJ — Class 150 / 300 / 400 / 600 / 900 / 1500 / 2500 |
| ASME/ANSI B16.47 | WN, Blind [Series A & B] — Class 75 / 150 / 300 / 400 / 600 / 900 |
| ASME/ANSI B16.36 | Orifice flanges — WN, SO, TH — Class 300 / 600 / 900 / 1500 / 2500 |
| DIN Flanges | DIN 2527, 2566, 2573, 2576, 2631–2638, 2641, 2642, 2655, 2656, 2673 — PN6 to PN100 |
| BS 4504 / BS 1560 / BS 10 | WN, SO, Plate, Blank — PN 2.5 to PN 400 / Tables D, E, F, H |
| Face Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Size Range | NPS ½″ to 60″ |
C-276 and C-22 for reactors, distillation columns, heat exchangers, and piping handling HCl, H₂SO₄, HNO₃, phosphoric acid, and mixed-acid streams. B-2/B-3 for pure HCl production and handling equipment.
Hastelloy C-276 and C-22 for multi-purpose pharmaceutical reactors, vitamin production plants, and API synthesis equipment requiring corrosion resistance across a wide range of cleaning and reaction chemistries.
Hastelloy C-276 for sour gas scrubbing systems, amine treating units, and offshore gas processing where H₂S, CO₂, and chlorides combine. C-22 for wet gas scrubber flanges and chloride-containing sour environments.
Hastelloy X for gas turbine combustion liners, transition ducts, afterburner flanges, and industrial furnace components operating in hot oxidising and combustion atmospheres to 1200°C.
Hastelloy C-276 and C-22 for FGD (Flue Gas Desulphurisation) absorber flanges and scrubber inlet connections where hot dilute H₂SO₄ with chlorides attacks conventional stainless steels rapidly.
Hastelloy C-276 for hazardous waste incinerator flange connections handling HCl-rich flue gases. C-22 for scrubber circuits in municipal waste-to-energy plants where mixed oxidising and chloride environments exist simultaneously.
What are the ASTM standards and UNS numbers for Hastelloy flanges?
All Hastelloy grades are manufactured to ASTM B564 (nickel alloy forgings): C-276 (N10276), C-22 (N06022), C-4 (N06455), C-2000 (N06200), B-2 (N10665), B-3 (N10675), and Hastelloy X (N06002). ASME boiler-code equivalent is ASME SB564. PMI (Positive Material Identification) is strongly recommended given that these grades are visually indistinguishable from each other and from lower-cost Inconel or stainless steel alloys.
What is the difference between Hastelloy C-276 and C-22?
C-276 (14.5–16.5% Cr) and C-22 (20–22.5% Cr) are both Ni-Cr-Mo-W alloys. The higher chromium in C-22 gives it superior resistance to oxidising acids (hot nitric, wet chlorine, chromic acid) and better pitting and crevice corrosion resistance. C-276 has a slight advantage in purely reducing environments. When in doubt between the two, C-22 is the safer choice as it performs well across a wider range of acid chemistries.
What is the fundamental difference between C-series and B-series Hastelloy?
C-series (C-276, C-22, C-4, C-2000) are Ni-Cr-Mo alloys — the Cr content (14–24%) gives resistance to both oxidising and reducing environments. B-series (B-2, B-3) are Ni-Mo alloys with no chromium — unrivalled for pure HCl and reducing H₂SO₄, but corrode rapidly in any oxidising medium. Specifying B-series in an environment that is or can become oxidising is a critical engineering error — always use C-series for mixed or uncertain media.
Can Hastelloy B-2 be used in oxidising environments?
No — absolutely not. Hastelloy B-2 (UNS N10665) contains no chromium and will corrode rapidly in any oxidising condition — including dissolved oxygen, ferric chloride, cupric ions, or oxidising acids. Even trace contamination with oxidising agents in an otherwise reducing acid stream can cause catastrophic corrosion. For any service that may be or become oxidising, specify C-276 or C-22. Hastelloy B-3 improves B-2's thermal stability but shares the same oxidising-environment restriction.
What welding consumable is used for Hastelloy C-276 flanges?
ERNiCrMo-4 (AWS A5.14) bare wire for GTAW/GMAW, and ENiCrMo-4 (AWS A5.11) covered electrode for SMAW. C-22 uses ERNiCrMo-10/ENiCrMo-10; B-2 uses ERNiMo-7; Hastelloy X uses ERNiCrMo-2. No preheat required for any Hastelloy grade; maximum interpass temperature 175°C. Low heat input is important to avoid grain boundary precipitation, particularly in B-series alloys.
Does Hastelloy require PWHT after welding?
No — Hastelloy C-276, C-22, C-4, C-2000, and Hastelloy X do not require PWHT as standard practice. For Hastelloy B-2, a post-weld solution anneal at 1066–1093°C may be specified in the most severe HCl service to dissolve any HAZ grain-boundary precipitates. Hastelloy B-3 was specifically developed to eliminate this requirement in most applications — its modified composition provides better HAZ stability without post-weld annealing.
What ASME P-Number is assigned to Hastelloy C-276 and C-22?
Hastelloy C-276 (N10276), C-22 (N06022), and B-2 (N10665) are all P-Number 44 under ASME BPVC Section IX. Hastelloy X (N06002) is P-Number 45. A WPS qualified on P44 (C-276) does not cover P45 (Hastelloy X) — separate PQR qualifications are required. Always verify the P-Number and Group Number when setting up welding procedures for Hastelloy flange construction.
What is Hastelloy X and what is it used for?
Hastelloy X (UNS N06002) is a Ni-Cr-Mo-Fe alloy (~47% Ni, 20.5–23% Cr, 17–20% Fe, 8–10% Mo) designed for high-temperature oxidising service up to 1200°C. It is used in gas turbine combustion liners, afterburner flanges, aircraft engine parts, industrial furnace flanges, and petrochemical reformer components. Unlike the C-series and B-series which are chosen for aqueous acid corrosion resistance, Hastelloy X is selected purely for its high-temperature strength and oxidation resistance in combustion atmospheres.
How does Hastelloy C-276 compare to Inconel 625 for corrosion resistance?
Hastelloy C-276 (15–17% Mo + 3–4.5% W) generally outperforms Inconel 625 (8–10% Mo) in reducing acid environments — particularly hot concentrated HCl and H₂SO₄ — due to its much higher Mo + W content. Inconel 625 (PREN ≈ 51) has broader approval in subsea and offshore specifications and superior high-temperature mechanical strength. For chemical process plants dealing with mineral acids, C-276 is typically the better choice; for offshore seawater and sour gas service, Inconel 625 is more commonly specified.
What pressure classes are available for Hastelloy flanges?
ASTM B564 Hastelloy flanges are available in ASME B16.5 pressure classes 150, 300, 400, 600, 900, 1500, and 2500 for NPS ½″ to 24″, and ASME B16.47 Series A & B for larger diameters. DIN pressure classes PN6 to PN100 are also available. Face types: RF, FF, RTJ. Tesco Steel manufactures all types — weld neck, blind, slip-on, socketweld, threaded, lap joint, and spectacle blind — from NPS ½″ to 60″ to order.
ASTM B564 • C-276, C-22, C-4, C-2000, B-2, B-3, Hastelloy X • All Types & Pressure Classes • Exported to 96 Countries
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