Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
Alloy C is the original nickel–molybdenum–chromium–tungsten corrosion-resistant alloy of the "C" family — the forerunner of the modern C-type alloys (C-276, C-22, C-4, C-2000). This datasheet presents the material within the American (ASTM / ASME) standard system.
It combines resistance to both oxidising and reducing acids, performing well in sulphuric, phosphoric and chlorine-contaminated acids, with significantly greater resistance to chloride stress-corrosion cracking than stainless steels. The high molybdenum content provides resistance to pitting and crevice corrosion, while the chromium content gives resistance in oxidising media — a combination that made it popular for chemical reactors, evaporators and transfer piping.
Important note: the original alloy C has relatively high carbon and silicon contents, which can lead to carbide precipitation in the weld heat-affected zone and reduced corrosion resistance in as-welded structures. For this reason it has been largely superseded by the low-carbon, low-silicon alloy C-276 (with a small tungsten addition) for as-welded service, and by alloy C-22 (higher chromium) for oxidising media. For new fabrications, C-276 or C-22 are normally specified; original alloy C is presented here for reference and legacy applications.
Typical values, solution-annealed condition (representative of the C family).
| Property | Value | Unit |
|---|---|---|
| Density | 8.7–8.9 | g/cm³ |
| Melting range | 1325–1370 | °C |
| Young's modulus (20 °C) | ~205 | GPa |
| Magnetic response | Non-magnetic | — |
| Coefficient of thermal expansion | Low (vs stainless) | — |
| Hardness (solution-annealed) | 88–96 | HRB |
| Structure | Austenitic (FCC) | — |
Nominal composition per ASTM B574 (C-family Ni-Cr-Mo-W).
| Element | Symbol | Value | Role in Alloy |
|---|---|---|---|
| Nickel | Ni | Balance | Base element; corrosion resistance |
| Molybdenum | Mo | 15–17 | Pitting/crevice + reducing-acid resistance |
| Chromium | Cr | 15–16 | Oxidising-media resistance; passive film |
| Iron | Fe | 4–7 | Present |
| Tungsten | W | 3–4.5 | Localised-corrosion resistance |
| Cobalt | Co | ≤2.5 | Residual |
| Carbon | C | ~0.04–0.08 | Higher than C-276 (HAZ sensitisation risk) |
| Silicon | Si | ~0.5–1.0 | Higher than C-276 |
| Manganese | Mn | ≤1.0 | Deoxidiser |
| Vanadium | V | ~0.2–0.4 | Carbide former |
Note: the higher carbon and silicon (vs alloy C-276) are the reason this original grade is prone to weld HAZ attack.
Typical room-temperature properties, solution-annealed condition.
| Property | Value | Source |
|---|---|---|
| Ultimate tensile strength | 690–785 MPa | C-family representative |
| 0.2% proof strength (yield) | 280–355 MPa | C-family representative |
| Elongation at break | 40–50 % | C-family representative |
| Hardness | 88–96 HRB | Solution-annealed |
The alloy is solid-solution-strengthened (not age-hardenable). Values are representative of the C family; for specification purposes use the modern grade (C-276) data and mill test certificate.
| Environment | Performance | Notes |
|---|---|---|
| Oxidising + reducing acids | Excellent | Combined Cr (oxidising) + Mo (reducing) |
| Sulphuric / phosphoric acid | Excellent | Strong acid resistance |
| Chlorine-contaminated acids | Very Good | Mo + W content |
| Pitting / crevice corrosion | Very Good | High molybdenum content |
| Chloride SCC | Very Good | Far better than stainless steels |
| Weld HAZ (as-welded) | Caution | Higher C/Si than C-276 — prone to HAZ carbide precipitation |
| Oxidising media (strong) | Good | Better served by higher-Cr alloy C-22 |
A solid-solution Ni-Cr-Mo-W alloy; not age-hardenable. Heat treatment is solution annealing only.
Solution Anneal Temperature: ~1200–1230 °C, followed by rapid cooling (water quench) Purpose: dissolves carbides/secondary phases, restores corrosion resistance and ductility.
Service caution: the higher carbon/silicon of the original grade promotes carbide precipitation in the weld HAZ; a post-weld solution anneal is advisable for aggressive service, or specify low-carbon alloy C-276 for as-welded use.
Weldable, but the original alloy C has a higher carbon and silicon content than C-276, so the weld heat-affected zone is susceptible to carbide precipitation and reduced corrosion resistance. A post-weld solution anneal is recommended for aggressive acid service; for as-welded service the low-carbon alloy C-276 should be specified.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Good (PWHT advised) | AWS A5.14 ERNiCrMo-4 (alloy C-276 type) matching filler |
| GMAW / MIG | Good (PWHT advised) | AWS A5.14 ERNiCrMo-4 (alloy C-276 type) matching filler |
| SMAW / stick | Good (PWHT advised) | AWS A5.11 ENiCrMo-4 type electrode |
Keep joints clean; solution-anneal welded assemblies destined for severe corrosion service.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Work hardening | High rate (typical of Ni-Cr-Mo alloys); rigid setup, sharp tooling, positive rake |
| Cutting | Low speed, sufficient feed/depth to cut below work-hardened layer |
| Coolant | Ample flood coolant |
| Preferred condition | Solution-annealed |
Forming Processes
| Process | Notes |
|---|---|
| Hot forming | ~950–1230 °C; solution-anneal after hot forming |
| Cold forming | Cold-formable; high work-hardening rate; solution-anneal after heavy reductions |
| Post-fabrication | Solution-anneal welded/heavily-worked parts for severe-service corrosion resistance |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Chemical processing | Reactors, evaporators, transfer piping | Mixed oxidising/reducing acid resistance |
| Sulphuric / phosphoric acid | Process vessels and piping | Strong-acid resistance |
| Chlorine / chlorinated media | Process equipment | Pitting/crevice + Cl resistance |
| Legacy / replacement | Existing alloy-C installations | Compatibility with original-C components |
Note: for new equipment, alloy C-276 (as-welded service) or C-22 (oxidising media) are normally the preferred current-production choices.
| Product Form | ASTM Standard | ASME Code |
|---|---|---|
| Rod and bar | ASTM B574 | ASME SB-574 |
| Plate, sheet and strip | ASTM B575 | ASME SB-575 |
| Seamless pipe and tube | ASTM B622 | ASME SB-622 |
| Welded pipe | ASTM B619 | ASME SB-619 |
| Welded tube | ASTM B626 | ASME SB-626 |
| Fittings | ASTM B366 | ASME SB-366 |
| Welding consumables | AWS A5.14 ERNiCrMo-type matching filler | — |
Note: standards listed are those of the C-family Ni-Cr-Mo-W alloys; original alloy C (UNS N10002) is largely superseded by alloy C-276 (UNS N10276).
| Alloy | Ni % | Cr % | Mo % | Other | Best Used For |
|---|---|---|---|---|---|
| Alloy C | bal | 15–16 | 15–17 | W 3–4.5, C ~0.04–0.08 | Original C-family (largely superseded) |
| Alloy C-276 | bal | 14.5–16.5 | 15–17 | W 3–4.5, C ≤0.01 | Low-C/Si; as-welded mixed-acid service |
| Alloy C-22 | bal | 20–22.5 | 12.5–14.5 | W 2.5–3.5 | Higher Cr; best pitting/crevice, oxidising |
| Alloy C-4 | bal | 14–18 | 14–17 | Ti, low Fe/W | Thermal stability; SCC resistance |
| Alloy C-2000 | bal | 22–24 | 15–17 | Cu 1.6 | Most versatile; Cu for reducing acids |
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