Valve Material Reference
ASTM A351 CN7M / ASTM A182 (Alloy 20 / Carpenter 20) Valve
Alloy 20 (Carpenter 20Cb-3)Alloy 20 (also called Carpenter 20Cb-3, UNS N08020) is a nickel-iron-chromium alloy with additions of copper, columbium (niobium), and molybdenum developed specifically for maximum resistance to hot concentrated sulphuric acid (H₂SO₄).
Form
Both
Max Temp
+370°C (+700°F)
Min Temp
−29°C (−20°F)
Category
Nickel Alloy
Chemical Composition — ASTM A351 CN7M / ASTM A182 (Alloy 20 / Carpenter 20)
Temperature Range
−29°C to +370°C (−20°F to +700°F)
Maximum Temperature
+370°C (+700°F)
Minimum Temperature
−29°C (−20°F)
Equivalent Grades — ASTM A351 CN7M / ASTM A182 (Alloy 20 / Carpenter 20)
| Standard | Equivalent Grade |
|---|---|
| UNS | N08020 |
| ASTM | A351 CN7M (cast), A182 F20 (forged), A276 Type 20 (bar) |
| EN | X1NiCrMoCuN32-20-7 / 1.4538 |
Suitable Services
Sulphuric acid (H₂SO₄) at all concentrations: dilute, concentrated, oleum
Phosphoric acid manufacturing
Fertilizer and ammonium sulphate plants
Mixed acid (nitration acid) service
Chloride-contaminated acid process streams
Not Suitable For
Hydrofluoric acid (HF) — use Monel 400
Highly oxidising environments without acidic media
Temperatures above 370°C
Valve Body Applications
Sulphuric acid (H₂SO₄) service valve bodies across all concentrations
Phosphoric acid plant valves
Fertilizer plant valve bodies (superphosphate, ammonium sulphate)
Mixed acid (H₂SO₄ + HNO₃) pickling line valves
Trim Applications
Ball valve balls and seats — solid Alloy 20 or Alloy 20 overlay
Globe valve disc and seat — Alloy 20 bar stock
Typical Valve Types in ASTM A351 CN7M / ASTM A182 (Alloy 20 / Carpenter 20)
Ball valves: sulphuric acid service, Class 150–600
Gate valves: phosphoric acid plant
Globe valves: fertilizer plant acid service
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Technical Reference
Industry Applications · 10 min read
How to Specify Industrial Valves for Chemical Service: A Complete Guide
Chemical plants handle some of the most aggressive fluids in any industry — strong acids, chlorinated solvents, caustic solutions, oxidising agents, and toxic gases. Specifying the wrong valve body material, seat, or seal material can lead to catastrophic corrosion, product contamination, or unsafe failure. This guide covers every variable in chemical valve specification.
All Valve Materials
Need ASTM A351 CN7M / ASTM A182 (Alloy 20 / Carpenter 20) Valves?
We supply ASTM A351 CN7M / ASTM A182 (Alloy 20 / Carpenter 20) (Alloy 20 (Carpenter 20Cb-3)) gate valves, globe valves, ball valves, check valves, and more. Full certification documentation — EN 10204 3.1/3.2 MTCs, hydro test certs — as standard.