Most C276 plate data sheets give you the same eight things: nickel balance, 15–17% Mo, 14.5–16.5% Cr, 3–4.5% W, tensile 690 MPa min, ASTM B575, solution annealed, density 8.89 g/cm³. That is the spec sheet. What it does not tell you is why a 12 mm C276 plate costs less than a 16 mm C22 plate for the same reactor shell, why your fabricator cannot weld C276 plate with the same procedure as 316L plate, and why "FGD absorber inlet zone" calls for C276 while "FGD absorber outlet zone" often calls for C22 or 625 instead - same alloy family, different sections of the same vessel.
What the Spec Sheet Says vs What It Means
ASTM B575 / ASME SB-575 covers nickel and nickel-base alloy plate, sheet, and strip for general corrosion-resistant service. For UNS N10276 (C276), the spec sheet numbers are:
| Element / Property | ASTM B575 Limit (UNS N10276) | Typical Mill Heat | What the Difference Means |
|---|---|---|---|
| Nickel | Balance (~57) | 57 | The base; enough to suppress chloride SCC |
| Chromium | 14.5 – 16.5% | 15.5 | Resistance to oxidizing media (HNO3, ferric chloride) |
| Molybdenum | 15.0 – 17.0% | 16.0 | Resistance to reducing acids (HCl, H2SO4) and pitting |
| Tungsten | 3.0 – 4.5% | 3.8 | Adds pitting resistance; partial substitute for Mo |
| Iron | 4.0 – 7.0% | 5.5 | Balance; keeps cost below higher-Ni alloys |
| Cobalt | ≤ 2.5% | 1.0 | Residual; not functional |
| Manganese | ≤ 1.0% | 0.5 | Deoxidation |
| Carbon | ≤ 0.010% | 0.005 | Very low to prevent HAZ sensitization |
| PREN (calculated) | ~ 68 | ~ 68 | Threshold for "nickel alloy" performance |
| Tensile strength, min | 690 MPa (100 ksi) | 720–790 MPa | ~ 2.2× the tensile of 316L |
| Yield strength (0.2%), min | 283 MPa (41 ksi) | 310–355 MPa | ~ 1.7× the yield of 316L |
| Elongation, min | 40% | 45–50% | High ductility for forming and rolling |
| Density | 8.89 g/cm³ (0.321 lb/in³) | - | Heavier than carbon steel by ~10%; affects vessel weight calc |
| Melting range | 1325 – 1370 °C | - | Welding window above 1050 °C |
The three numbers that decide whether C276 is right for your service are chromium (oxidizing resistance), molybdenum (reducing acid + pitting resistance), and PREN (chloride pitting equivalent). Together, those three put C276 in the "resists almost everything except hot concentrated HNO3 and HF" bucket. If your service is reducing acid (HCl, dilute H2SO4), wet chlorine, or mixed acid with chlorides, C276 is the conservative choice.
Why Buy C276 Plate Instead of C22 or 625 Plate
For most buyers, the comparison is not C276 vs C22. It is C276 vs 316L, or C276 vs C22, or C276 vs 625. The answer comes down to the chemistry of the service.
| Service Scenario | Best Plate | Why C276 Is (or Is Not) the Right Call |
|---|---|---|
| FGD absorber inlet (Cl⁻ 30,000 – 50,000 ppm, 60 – 80 °C, pH 2 – 4, fly ash slurry) | C276 (or C22) | High Mo + W handle the chloride slurry reducing-acidity; C22 is competitive on the oxidizing zones |
| FGD absorber outlet (Cl⁻ 5,000 ppm, 50 °C, pH 4 – 6, no slurry) | C22 or 625 | Lower chloride, oxidizing conditions favor higher-Cr alloys |
| Phosphoric acid evaporator (H3PO4 30 – 50% with HF/SiF6 impurities, 100 – 150 °C) | C276 | Mo + W handle the fluoride-bearing acid; only C276 and C2000 are qualified for this |
| Sulfuric acid cooler (H2SO4 50 – 98%, 60 – 120 °C) | C276 | Mo + W dominate reducing sulfuric; C22 fails above 60% concentration |
| Wet chlorine piping/equipment (Cl2 + water, ambient – 60 °C) | C276 | Industry standard for wet Cl2; only C22 is competitive |
| Pharmaceutical reactor (organic acids + chloride catalysts, 50 – 150 °C) | C276 | Mixed organic + chloride + acid; C276 is the conservative choice |
| Hot concentrated nitric acid (HNO3 > 70%, > 80 °C) | NOT C276 (use 304L or higher-Cr alloy) | C276 Cr is too low; oxidizing HNO3 attacks |
| Hydrofluoric acid (HF > 10%) | NOT C276 (use Monel 400) | HF attacks Ni-Mo alloys |
| Seawater plate heat exchanger (ambient – 40 °C) | NOT C276 (use 625 or titanium) | C276 is overkill; 625 is cheaper and equally resistant |
The pattern is clear: C276 is the right plate when the service is reducing + chloride + acid - wet chlorine, FGD reducing zone, phosphoric acid, mixed acid with chlorides. C22 wins on oxidizing + mixed-acid services (concentrated HNO3, FGD oxidizing zone). 625 wins on seawater + high-strength services where pitting resistance and strength matter more than acid resistance.
Thickness, Sizes and Forms Available
We supply C276 plate to ASTM B575 / ASME SB-575 in the following range. Other thicknesses and cut-to-size available on request.
| Form | Thickness Range | Width Range | Length Range | Finish |
|---|---|---|---|---|
| Hot rolled plate (HRAP) | 3.0 – 100 mm (4.8 – 76.2 mm most stocked) | 1000 – 2500 mm (up to 3000 mm) | 2000 – 12000 mm | No.1 (HR, annealed, pickled) |
| Cold rolled sheet | 0.3 – 6.0 mm | 1000 – 1500 mm | 2000 – 6000 mm | 2B, BA, No.4, mirror |
| Plate for chemical reactor shells (heavy) | 6 – 50 mm | up to 2500 mm | up to 8000 mm | No.1, machined faces |
| Clad plate (C276 on carbon steel base) | 6 – 50 mm total | up to 2500 mm | up to 8000 mm | No.1 / 2B on C276 face |
| Plasma / laser cut plate | As above | Custom | Custom | As-rolled or pickled |
The standard plate thickness range we keep in stock is 6 mm to 50 mm, which covers most chemical reactor and FGD absorber shell applications. Below 6 mm becomes "sheet" territory (cold rolled, 2B finish). Above 50 mm we order to size for the specific project; heavy plate (>50 mm) requires special rolling and solution annealing, with lead time 8–14 weeks.
Note on clad plate: For large-diameter reactor shells where solid C276 plate would be cost-prohibitive, C276/carbon-steel clad plate uses a 3–6 mm C276 cladding layer metallurgically bonded to a carbon steel base. The total plate is 6–50 mm with C276 on the process side. The clad plate qualification follows ASME Section IX with separate WPS for the C276 cladding and the C-steel base. This is the typical choice for FGD absorber shells above 4 m diameter.
Standards, Certification and Documentation
For chemical reactor, FGD, and pharmaceutical applications, C276 plate is supplied to the following standards:
| Standard | Scope | Typical Use |
|---|---|---|
| ASTM B575 / ASME SB-575 | Nickel-base alloy plate, sheet, strip for general corrosion-resistant service | Most common; default |
| ASTM B574 | Nickel-base alloy rod and bar (companion to B575 for fittings) | Companion standard |
| EN 10028-7 | Flat products for pressure purposes | European pressure vessel |
| EN 10095 | Heat-resistant steels and nickel alloys | European high-temperature |
| Werkstoff 2.4819 | German material number | European designation |
| NACE MR0175 / ISO 15156-3 | Sour service (H2S) compliance | Oil & gas, hard ≤ 35 HRC typical |
| ASTM G28 Method A | Intergranular corrosion resistance (oxidizing medium) | For oxidizing service verification |
| ASTM A262 Practice E | Intergranular corrosion for nickel alloys | For welded fabrication |
Documentation shipped with every C276 plate order:
| Document | Standard | Typical For |
|---|---|---|
| Mill Test Certificate (MTC) | EN 10204 3.1 or 3.2 | All shipments |
| Chemistry check (Ni balance, Cr 14.5-16.5%, Mo 15-17%, W 3-4.5%, Fe 4-7%, C ≤ 0.010%) | ASTM B575 | All shipments |
| Mechanical test report (tensile, yield, elongation, hardness) | ASTM A370 | All shipments |
| Solution annealing record (1121-1177°C + rapid water quench) | Mill process record | All shipments |
| Intergranular corrosion test | ASTM G28 Method A | Oxidizing service verification |
| Country of origin / mill location | Customs | EU and GCC imports |
| PED conformity (for EU pressure equipment) | PED 2014/68/EU | European delivery |
For European delivery to Italy / Porto Marghera / Milan chemical industry, PED conformity for pressure-bearing plate is required. For Italian FGD installations, EN 10028-7 reference is typically standard. For pharmaceutical reactor applications, traceability per EU GMP Annex 11 is increasingly requested.
Welding Notes (Plate vs Pipe)
Plate welds behave differently from pipe welds, and the fabricator's WPS must reflect this.
| Difference | Pipe Welding | Plate Welding |
|---|---|---|
| Position | All positions (6G qualified) | Mostly flat (1G) and horizontal (2G) |
| Joint type | Butt weld, branch connection | Butt weld, fillet weld, lap joint, tubesheet-to-shell |
| Filler | ERNiCrMo-4 (C276 filler) | ERNiCrMo-4 (same) |
| Heat input | 0.5 – 1.5 kJ/mm typical | 0.5 – 1.5 kJ/mm typical |
| Interpass temperature | ≤ 150°C | ≤ 150°C |
| PWHT | Never (low C content, C276 resists HAZ sensitization) | Never |
| Intergranular corrosion test | ASTM G28 Method A on weld coupon | ASTM G28 Method A on weld coupon |
The plate-specific risks to watch for: thick-plate welds (above ~25 mm) may require multiple passes with controlled interpass temperature (≤ 150°C); clad plate welds require separate WPS for the C276 cladding (ERNiCrMo-4 filler, 0.5–1.5 kJ/mm) and the C-steel base (E7018 or E8018-C3 filler, conventional CS weld procedure) - and a transition weld at the cladding interface; tubesheet-to-shell welds are deep grooves with high restraint and risk of root cracking if the WPS is not qualified for the actual joint geometry.
What to put in your RFQ: "plate to be welded per ASME Section IX qualified WPS using ERNiCrMo-4 filler, heat input 0.5–1.5 kJ/mm, interpass temperature ≤ 150°C, ASTM G28 Method A intergranular corrosion test on PQR coupon, no PWHT."
Where C276 Plate Is Used
- Heat treatment industry: furnace rollers, muffles, radiation tubes, baskets, fan blades, air guide plates, quenching fixtures.
- Chemical and petrochemical: high-temperature cracking furnace tubes (specific environments), converter components, catalyst support grids, high-temperature valve flange gaskets, heat exchangers (high-temperature sections).
- Aerospace: combustion chamber components (flame tubes, transition sections), thrust reverser insulation structures, high-temperature fasteners.
- Energy and power: gas turbine combustion chamber liners, thermal barrier coating substrates, boiler key high-temperature components, and certain auxiliary systems for nuclear power.
- Glass and ceramic manufacturing: furnace rollers, furnace doors, burners, and hot end conveying components.
- Environmental engineering: high-temperature areas of flue gas desulfurization (FGD) systems, and waste incinerator components.
- Industrial furnace manufacturing: as the core material of high-performance furnace heat-resistant steel.
The decision rule for upgrading from C276 plate to C22 plate: when the service shifts from reducing-acid + chloride to oxidizing-acid + chloride, or when ASTM G28 Method A on the C276 weld shows borderline intergranular attack. C22 has higher Cr (20–22.5% vs 14.5–16.5%) and a metallurgy-engineered HAZ that handles oxidizing mixed acids better.
The decision rule for downgrading from C276 plate to 625 plate: when the service is seawater (ambient–40°C) without strong reducing acid. 625 is cheaper and has higher strength, and C276 is over-spec for plain seawater.
FAQ
What is C276 plate used for?
C276 plate (ASTM B575, UNS N10276) is used for chemical reactor vessels, FGD absorber shells, phosphoric acid evaporators, wet chlorine handling equipment, pharmaceutical API reactors, and other aggressive acid/chloride services. The 15–17% molybdenum and 3–4.5% tungsten give it exceptional resistance to reducing acids (HCl, dilute H2SO4), wet chlorine, and chloride-bearing mixed acids. It is the industry standard for the most aggressive corrosion service in chemical, FGD, and pharmaceutical industries.
What is the difference between C276 plate and C276 pipe?
C276 plate and C276 pipe have the same ASTM chemistry requirements (UNS N10276, ASTM B575 for plate / B622 for pipe, ASME equivalents). The difference is in the form: plate is flat-rolled with wrought banded microstructure, pipe is either seamless (extruded + drawn) or welded (rolled + formed + welded). For a chemical reactor shell, plate is the natural choice. For the connecting piping, pipe is the natural choice. The chemistry is identical; the form dictates the application.
What is the difference between C276 plate and C22 plate?
C276 has 15–17% Mo and 14.5–16.5% Cr - better in reducing acids (HCl, H2SO4) and chloride pitting. C22 has 12.5–14.5% Mo and 20–22.5% Cr - better in oxidizing acids (HNO3, mixed acid) and weld HAZ corrosion resistance. For FGD absorber reducing zones and wet chlorine, choose C276. For FGD oxidizing zones and mixed acid, choose C22. They are not interchangeable.
Can C276 plate be welded?
Yes. C276 is welded using ERNiCrMo-4 filler (AWS A5.14) per ASME Section IX qualified WPS, with heat input 0.5–1.5 kJ/mm, interpass temperature ≤ 150°C, and no PWHT (post-weld heat treatment would sensitize the HAZ). The low carbon content (≤ 0.010%) prevents HAZ sensitization in the as-welded condition - no need for solution annealing after welding.
What documentation should I require with C276 plate?
For chemical / FGD / pharmaceutical applications, request EN 10204 3.1 mill certificate (chemistry + mechanical properties), solution annealing record (1121-1177°C + rapid water quench), ASTM G28 Method A intergranular corrosion test report (for oxidizing service verification), country of origin, and dimensional inspection report. For European delivery to Italy / Germany / Netherlands, PED 2014/68/EU conformity assessment is required for pressure-bearing plate. For pharmaceutical applications, EU GMP Annex 11 traceability documentation is increasingly requested.
Does C276 plate have a maximum service temperature?
For corrosion service, approximately 675°C in oxidizing atmospheres and up to 1093°C in short-term exposure. Above 400°C in reducing atmospheres, C276 can suffer from sigma-phase precipitation over extended service. For continuous high-temperature service above 600°C, consider Inconel 625 plate (continuous to 980°C) or Hastelloy X plate.
How does C276 plate compare to titanium for FGD absorber shells?
Titanium (Grade 2 or Grade 7) has been used historically for FGD absorber shells and is more resistant to chloride pitting at lower cost. However, titanium is susceptible to crevice corrosion in FGD fly ash deposits, and it cannot handle reducing acid excursions. C276 handles reducing + chloride + acid combinations that attack titanium. For FGD reducing zones with high fly ash, C276 is the conservative choice.
Need Hastelloy C276 plate (UNS N10276) to ASTM B575 with the right thickness range, finish, certification, and mill origin for your chemical reactor, FGD absorber, or pharmaceutical vessel?
HUITONG supplies C276 hot rolled plate (3–100 mm) and cold rolled sheet (0.3–6.0 mm) to ASTM B575 / ASME SB-575, with EN 10204 3.1 / 3.2 certificates, ASTM G28 Method A test report, PED conformity for European pressure equipment, and clad plate (C276/carbon steel) for large-diameter reactor shells. Send your thickness, width, length, finish, quantity, and target certification level to market@htpipe.com or WhatsApp +86-19339900201 - and if you are unsure whether C276 plate is the right grade (or whether you actually need C22, 625, or 316L), tell us the service (chloride, acid type, temperature, pressure vessel code, industry) and we will tell you the minimum-cost grade that qualifies.
