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Alloy 20 (Carpenter 20) Pipe Fittings and Flanges
Alloy 20 (Carpenter 20) copper-nickel-chromium-molybdenum pipe fittings and flanges to ASME SB-462, SB-461 and SA-351. Cu-Ni-Cr-Mo alloy for sulfuric acid, hydrochloric acid, pulp bleaching and fine chemical service.
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Alloy 20 — also known as Carpenter 20 — is a copper-nickel-chromium-molybdenum alloy developed for sulfuric acid and hydrochloric acid service. It is not a nickel alloy in the strict sense, but it behaves like one in the environments that destroy ordinary stainless steel.
We supply Alloy 20 in forged and cast forms, to ASME SB-462 (forgings), SB-461 (castings) and SA-351 (castings), in buttweld, socket weld and threaded configurations, plus raised face, flat face and weld neck flanges.
Why Alloy 20 rather than 316L or Hastelloy
The short answer is cost against service life. Hastelloy C-276 will handle almost anything Alloy 20 handles, and will handle several things Alloy 20 cannot. But C-276 is roughly four to six times the price of Alloy 20.
For sulfuric acid at moderate concentration and temperature — the dominant application — Alloy 20 gives you the corrosion resistance at a fraction of Hastelloy cost. Buyers typically specify Alloy 20 for:
- Sulfuric acid (H2SO4) pickling, acid transfer and dilution systems
- Hydrochloric acid (HCl) at concentrations where 316L and even 904L fail
- Pulp and paper bleaching equipment
- Explosive environments where spark resistance matters
- Pharmaceutical and fine chemical processing
If your stream is above 65% concentration or above 100 °C, talk to us before ordering — the grade boundary matters.
Material specification
Do not accept a generic “Alloy 20” on the purchase order. Write the standard and grade:
| Form | Specification | Grade designation |
|---|---|---|
| Forged fittings, flanges | ASME SB-462 / ASTM A462 | Alloy 20 (UNS N08020) |
| Cast fittings | ASME SB-461 / ASTM A461 | Alloy 20 (UNS N08020) |
| Cast fittings, valve bodies | ASME SA-351 / ASTM A351 | CN-7M |
| Forged bar, plate | ASME SB-336 / ASTM B336 | Alloy 20 |
ASME SB-462 covers forged or rolled UNS N08020 along with the other corrosion alloys — N06030, N06022, N06200, N06059, N10276 and more — so the certificate references the UNS number, not a trade name.
Product specifications
Buttweld fittings (ASME B16.9)
- Types: 90° and 45° elbows, concentric and eccentric reducers, equal and reducing tees, crosses, caps, laterals
- Size: NPS 1/2″ to NPS 24″ (DN 15 to DN 600) and above
- Wall: Schedule 5S to Schedule 160
- Pressure class: 150 to 2500
Socket weld and threaded fittings (ASME B16.11)
- Size: NPS 1/2″ to NPS 4″
- Pressure class: 2000, 3000, 6000 WOG
- Thread: ASME B1.20.2 NPT tapered
Flanges (ASME B16.5 / B16.47)
- Types: weld neck, slip-on, threaded, blind, lap joint
- Faces: raised face (RF) and flat face (FF)
- Class: 150 to 2500
Certification and testing
- EN 10204 3.1 standard; 3.2 available with third-party witness
- PMI by XRF — we recommend this on mixed-grade jobs, because Alloy 20 and 316L are visually identical
- Hydrostatic shell test
- Chemical analysis on every heat
- Heat number stamped and traceable on every fitting
Ordering information
Send us item type, size (NPS and DN), wall thickness or class, quantity, and the destination port. We quote FOB Hefei, Ningbo or Shanghai as standard, and CIF/DAP on request. Most stock Alloy 20 items ship within 2 to 4 weeks; heavy wall and large diameter add 2 to 3 weeks.
