Project Description

Alloy C276 (UNS N10276), also designated W.Nr. 2.4819 / EN NiMo16Cr15W, is a nickel-chromium-molybdenum-tungsten solid-solution superalloy renowned as the industry workhorse for the most aggressive chemical and petroleum environments. Its ultra-low carbon content (≤0.010%) suppresses grain-boundary carbide precipitation in the weld heat-affected zone, enabling use in the as-welded condition. With a Pitting Resistance Equivalent Number (PREN) of ≥74 and qualification under NACE MR0175 / ISO 15156 Level VII for sour service, Alloy C276 is the benchmark CRA for upstream tubing, casing, and liners exposed to high H2S, CO2, elemental sulfur, and chloride brines. At SHUNFU METAL, Alloy C276 pipes are manufactured through vacuum induction melting (VIM) followed by electroslag remelting (ESR), ensuring ultra-clean ingots free of deleterious phases. Every heat undergoes 100% positive material identification (PMI), immersion ultrasonic testing, eddy current inspection, hydrostatic testing, and dimensional verification prior to certified release.

Equivalent & Similar Grades to Alloy C276

The following table cross-references Alloy C276 with advanced Ni-Cr-Mo alloys commonly specified for sour petroleum service across global standard systems.

Alloy UNS EN / W.Nr. DIN GB JIS GOST Key ASTM PREN
Alloy C276 N10276 2.4819 / NiMo16Cr15W 2.4819 NS3304 NW 0276 XH65MBY B622 / B619 ≥74
Alloy C-22 N06022 2.4602 / NiCr21Mo14W 2.4602 NS3308 NW 6022 — B574 / B622 ≥67
Alloy 59 N06059 2.4605 / NiCr23Mo16Al 2.4605 NS3311 NW 6059 — B622 / B619 ≥74
Alloy 625 N06625 2.4856 / NiCr22Mo9Nb 2.4856 NS3306 NCF 625 XH75MBTYU B444 / B705 ≥46
Alloy C-4 N06455 2.4610 / NiMo16Cr16Ti 2.4610 NS3355 NW 6455 — B622 / B619 ≥60
Alloy 686 N06686 2.4606 / NiCr21Mo16W4 2.4606 NS3309 NW 686 — B622 / B619 ≥80

Oil & Gas Applications of Alloy C276 Pipe

Alloy C276 is qualified under NACE MR0175 / ISO 15156 for the most severe sour service environments and is widely specified where other CRA grades experience pitting, crevice corrosion, or SCC in aggressive acid-chloride-H2S systems.

Sour Service Downhole Tubing & Casing

Production tubing and casing in HP/HT wells with H2S > 10 mol%, CO2, elemental sulfur, and chlorides exceeding 200,000 ppm—NACE Level VII qualified.

Subsea Flowlines & Export Risers

CRA-clad and solid C276 flowlines for subsea tiebacks transporting wet, sour multiphase production fluids with high chlorides and elemental sulfur deposits.

Chemical Injection & Methanol Lines

High-integrity chemical injection tubing for corrosion inhibitors, methanol, and H2S scavengers—resists halide acids and oxidizing chemical species.

FGD Scrubber & Duct Piping

Wet FGD absorber vessels, spray headers, and ductwork in refinery and power plant SO2 scrubbing systems—resists sulfuric/chloride condensate corrosion.

Acid Gas Removal (AGR) Unit Piping

Rich/lean amine piping, heat exchanger tubes, and reclaimer tubing in amine sweetening plants—resists amine degradation acids and wet CO2 corrosion.

Sour Water Stripper Overhead Systems

Overhead vapour lines, condenser tube bundles, and pump-around piping in sour water strippers handling H2S, NH3, and cyanide-laden streams.

Wellhead & Subsea Valve Internals

Valve stems, seat rings, gate/ball and choke valve trim, and instrument tubing for HP/HT wellhead and subsea tree assemblies—NACE MR0175 certified.

Geothermal Acid Well Production Casing

Production casing in high-temperature geothermal wells with mixed acid condensates—resists pitting and crevice corrosion in H2S/CO2/chloride brines up to 260 °C.

Sand Screen Base Pipe & Swell Packers

Perforated base pipe for premium sand control screens and mandrel tubing for swellable packer assemblies in deepwater HP/HT completions.

Alloy C276 Pipe Supply Range — SHUNFU METAL

Alloy C276 seamless CRA pipe
SHUNFU Alloy C276 Seamless Pipe

SHUNFU METAL maintains a comprehensive inventory of Alloy C276 pipe in both seamless and welded product forms to ASTM B622, ASTM B619, and ASME SB-622/SB-619 specifications. All products are supplied with EN 10204 3.1 or 3.2 certification, full heat traceability, and NACE MR0175 / API 6ACRA compliance documentation.

  • Seamless Pipe: OD 4 mm – 219 mm (⅟” – 8″), WT 0.5 mm – 20 mm
  • Welded Pipe: OD 5 mm – 1219 mm (⅟” – 48″), WT 1.0 mm – 15 mm
  • Heavy Wall: OD 10 mm – 600 mm, WT up to 100 mm for high-pressure downhole service
  • Capillary & Instrument Tube: OD 0.4 mm – 16 mm, WT 0.1 mm – 3.0 mm
  • Schedule Range: SCH 5S, SCH 10S, SCH 40S, STD, SCH 80S, SCH 160, XXS per ASME B36.10 / B36.19
  • Length: Up to 12 m (single random, double random, or precision cut-to-length)
  • End Finish: Plain end, beveled end (37.5° per ASME B16.25), threaded (NPT/BSP)
  • Surface Condition: Solution annealed & pickled, bright annealed, cold-drawn, polished (Ra ≤ 0.8 µm)
  • Certification: NACE MR0175 / ISO 15156 Level VII, API 6ACRA, VdTÜV 292, PED 2014/68/EU

Chemical Composition of Alloy C276 (ASTM B622 / B619)

Alloy C276 is a Ni-Cr-Mo-W system alloy with extremely low carbon and silicon to suppress M23C6 and mu-phase precipitation at grain boundaries. The 4% tungsten addition synergizes with 16% molybdenum to deliver superior resistance to localized corrosion in oxidizing halide environments, while the high nickel content (>57%) provides metallurgical stability and resistance to chloride SCC.

Ni Cr Mo W Fe Mn Si Co V C P S
Bal (~57) 14.5–16.5 15.0–17.0 3.0–4.5 4.0–7.0 ≤1.00 ≤0.08 ≤2.50 ≤0.35 ≤0.010 ≤0.040 ≤0.030

All values in weight percent (wt%). The ultra-low carbon (≤0.010%) is critical—it prevents intergranular sensitization during welding, allowing Alloy C276 to be placed in service without post-weld heat treatment. The synergistic Mo + W combination (total pitting resistance index ≥74) delivers exceptional crevice corrosion resistance in oxidizing chloride environments. SHUNFU METAL confirms every heat with full optical emission spectroscopy (OES) plus inert gas fusion for carbon/sulfur and inductively coupled plasma (ICP) analysis for trace elements.

Mechanical Properties of Alloy C276 Pipe (Solution Annealed)

Properties at ambient temperature for solution-annealed condition (1121 °C / 2050 °F, followed by rapid water quench). Alloy C276 is a solid-solution alloy—it cannot be strengthened by precipitation hardening and derives mechanical strength from cold working only. The annealed condition provides an optimal balance of strength, ductility, and corrosion resistance.

Property Metric Imperial
Tensile Strength, Rm 690 MPa min 100 ksi min
Yield Strength, Rp0.2 290 MPa min 41 ksi min
Elongation (2″ / 50.8 mm) 40% min 40% min
Hardness ≤100 HRB / ≤215 HBW ≤100 HRB
Elastic Modulus 205 GPa 29.8 × 106 psi
Density 8.89 g/cm3 0.321 lb/in3
Melting Range 1325–1370 °C 2415–2500 °F
Thermal Conductivity (20 °C) 11.1 W/m·K 77 Btu·in/h·ft2·°F
Service Temperature −270 to +400 °C −455 to +750 °F

SHUNFU METAL solution-anneals every pipe in computer-controlled furnaces with furnace-chart recording for full thermal traceability. Each lot undergoes destructive mechanical testing—tensile, hardness, and flattening/flaring per ASTM B622/B619—on representative samples. Supplementary intergranular corrosion testing per ASTM G28 (Method A, ferric sulfate–sulfuric acid) and grain-size metallographic analysis (ASTM E112, typically ASTM grain size 4–7) are performed routinely. Cold-pilgered tempers delivering yield strengths up to 120 ksi (827 MPa) are available for high-pressure downhole applications requiring enhanced collapse resistance.