ASTM B425/B425M is the standard specification by ASTM International covering nickel-iron-chromium-molybdenum-copper alloys in the form of hot-finished and cold-drawn rod, bar, and shapes. The most widely used grade is UNS N08825 (Alloy 825 / Incoloy 825). The companion specification ASME SB-425 adopts identical requirements for ASME Boiler and Pressure Vessel Code (BPVC) compliance.
Zhengzhou Huitong (HT Pipe) supplies ASTM B425 / SB-425 compliant nickel alloy rods and bars with full Mill Test Certificates (MTC) per EN 10204 3.1.
1. Standard Scope & Designation
ASTM B425/B425M covers nickel-iron-chromium-molybdenum-copper alloy rod and bar in four UNS grades:
| UNS No. |
Common Name |
Product Forms |
Processing |
| UNS N08825 |
Alloy 825 / Incoloy 825 |
Rounds, squares, hexagons, rectangles |
Hot-finished, Cold-drawn |
| UNS N08221 |
High-Mo Alloy 825 variant |
Rounds, squares, hexagons, rectangles |
Hot-finished, Cold-drawn |
| UNS N06845 |
Ni-Fe-Cr-Mo-Cu alloy |
Rounds, squares, hexagons, rectangles |
Hot-finished, Cold-drawn |
| UNS N08827 |
Ni-Fe-Cr-Mo-Cu alloy |
Rounds, squares, hexagons, rectangles |
Hot-finished, Cold-drawn |
Scope Statement (ASTM B425-26): "This specification covers nickel-iron-chromium-molybdenum-copper alloys (UNS N06845, UNS N08221, UNS N08825, and UNS N08827) in the form of hot-finished and cold-drawn rounds, squares, hexagons, and rectangles for general corrosive service."
| Designation |
Issuing Body |
Unit System |
Latest Edition |
| ASTM B425 |
ASTM International |
Inch-Pound |
B425/B425M-26 |
| ASTM B425M |
ASTM International |
SI (Metric) |
B425/B425M-26 |
| ASME SB-425 |
ASME (BPVC Sec. II Part B) |
Both |
2025 Edition |
2. Alloy Grades Covered by ASTM B425
ASTM B425 covers four nickel-iron-chromium-molybdenum-copper alloys in the austenitic family:
| UNS No. |
Commercial Designation |
Alloy Type |
Key Features & Typical Application |
| UNS N08825 |
Alloy 825 / Incoloy 825 |
Ni-38-46%, Cr-19.5-23.5%, Mo-2.5-3.5%, Cu-1.5-3.0%, Ti-stabilized |
General corrosion resistance — chemical process, oil & gas, offshore, FGD, nuclear reprocessing |
| UNS N08221 |
High-Mo 825 variant |
Ni-39-46%, Cr-20-22%, Mo-5.0-6.5%, Cu-1.5-3.0%, Ti-stabilized, C≤0.025% |
Enhanced pitting resistance — aggressive chloride and reducing acid service |
| UNS N06845 |
Ni-Fe-Cr-Mo-Cu alloy |
Modified Ni-Fe-Cr-Mo-Cu chemistry |
Specialized corrosion service |
| UNS N08827 |
Ni-Fe-Cr-Mo-Cu alloy |
Modified Ni-Fe-Cr-Mo-Cu chemistry |
Specialized corrosion service |
3. Chemical Composition — Key Grades (ASTM B425, Table 1)
Values are maximum unless shown as a range. "—" = not required / not applicable. Heat analysis per ASTM B425.
| Grade |
Ni% |
Fe% |
Cr% |
Mo% |
Cu% |
Ti% |
C% |
Mn% |
Si% |
S% |
Al% |
| N08825 |
38.0–46.0 |
≥22.0 |
19.5–23.5 |
2.5–3.5 |
1.5–3.0 |
0.6–1.2 |
0.05 |
1.00 |
0.50 |
0.03 |
0.20 |
| N08221 |
39.0–46.0 |
22.0–33.9 |
20.0–22.0 |
5.0–6.5 |
1.5–3.0 |
0.6–1.0 |
0.025 |
1.00 |
0.050 |
0.03 |
0.20 |
Note: Full chemistry for UNS N06845 and UNS N08827 per ASTM B425-26 Table 1. Product analysis tolerances per ASTM B425 Section 7 apply.
4. Mechanical Property Requirements (ASTM B425, Table 2)
All values are minimum requirements in the annealed condition. Per ASTM B425/B425M.
| Grade |
UNS |
Tensile Strength
min MPa (ksi) |
Yield Strength 0.2%
min MPa (ksi) |
Elong.
min % |
Hardness
max |
| Alloy 825 |
N08825 |
586 (85) |
241 (35) |
30 |
200 HB |
| High-Mo |
N08221 |
610 (88) |
270 (39) |
34 |
200 HB |
Note: Hardness testing per ASTM E10 (Brinell) or ASTM E18 (Rockwell). Cold-drawn bar may exhibit higher strength due to cold work. Tensile testing per ASTM E8.
5. Heat Treatment Requirements
| Grade |
Condition |
Heat Treatment |
Cooling |
| UNS N08825 (Alloy 825) |
Annealed |
927–1010°C (1700–1850°F) |
Water quench or rapid air cool |
| UNS N08221 |
Annealed |
927–1010°C (1700–1850°F) |
Water quench or rapid air cool |
Important: Annealing is mandatory to dissolve carbides and restore optimal corrosion resistance. Alloy 825 should not be used at temperatures above 540°C (1000°F) for extended periods, as this may cause microstructural changes that reduce ductility and impact toughness. The titanium addition provides stabilization against intergranular corrosion after welding.
6. Testing & Inspection Requirements
| Test |
Requirement |
Reference Standard |
| Chemical Analysis (Heat) |
One per heat / melt; all elements per Table 1 |
ASTM E1473 / E354 |
| Tensile Test |
One per lot (same heat, same condition, same diameter group) |
ASTM E8 / E8M |
| Hardness Test |
Brinell or Rockwell; one per lot |
ASTM E10 / E18 |
| Intergranular Corrosion |
Supplementary requirement when specified |
ASTM A262 |
| Visual & Dimensional |
Surface condition, straightness, diameter tolerance |
ASTM B425 Tables 3–7 |
| PMI (Positive Material ID) |
When specified by purchaser |
ASTM E1473 |
7. Rod & Bar Dimensions — Available Sizes
ASTM B425 covers hot-finished and cold-drawn rod and bar. Common commercial size ranges:
| Form |
Diameter / Width |
Typical Length |
Tolerance |
| Hot-Finished Round |
12.7 – 200 mm (1/2–8 in.) |
3.0 – 6.0 m random |
±0.13 mm (±0.005 in.) typical |
| Cold-Drawn Round |
6.35 – 100 mm (1/4–4 in.) |
3.0 – 6.0 m random |
±0.05 mm (±0.002 in.) typical |
| Hot-Finished Square |
12.7 – 150 mm |
3.0 – 6.0 m random |
±0.25 mm typical |
| Hot-Finished Hexagon |
12.7 – 100 mm (AF) |
3.0 – 6.0 m random |
±0.25 mm typical |
Note: Diameter tolerances and out-of-roundness per ASTM B425 Tables 3–7. Cut-to-length available on request. Tighter tolerances negotiable.
8. Industries & Applications
| Industry |
Recommended Grades |
Typical Applications |
| Chemical Processing |
N08825, N08221 |
H₂SO₄, H₃PO₄ acid service, reactor internals, agitator shafts, valve stems |
| Oil & Gas / Offshore |
N08825, N08221 |
Downhole tubing, manifold piping, seawater heat exchangers, sour gas components |
| Power Generation (FGD) |
N08825 |
Flue gas desulfurization scrubbers, absorption tower internals, ductwork |
| Nuclear Industry |
N08825 |
Fuel reprocessing equipment, radioactive waste handling, dissolver vessels |
| Pharmaceutical |
N08825 |
Corrosion-resistant pump shafts, fasteners, mixing equipment |
| Steel Pickling |
N08825 |
Heating coils, baskets, tanks for acid pickling lines |
9. B425 vs B424 vs B423 — Ni-Fe-Cr-Mo-Cu Alloy Specifications Compared
| Criteria |
ASTM B425 |
ASTM B424 |
ASTM B423 |
| Product Form |
Rod, Bar, Shapes |
Plate, Sheet, Strip |
Seamless Pipe & Tube |
| Processing |
Hot-finished, Cold-drawn |
Hot-rolled, Cold-rolled |
Hot-finished, Cold-drawn |
| UNS Grades |
N08825, N08221, N06845, N08827 |
N08825, N08221, N06845 |
N08825, N08221, N06845 |
| Mechanical Props |
TS≥586 MPa, YS≥241 MPa (N08825) |
TS≥586 MPa, YS≥241 MPa (N08825) |
TS≥586 MPa, YS≥241 MPa (N08825) |
| General Requirements |
ASTM B880 |
ASTM B880 |
ASTM B880 |
| Primary Use |
Machined parts, fasteners, shafts |
Pressure vessels, heat exchangers |
Process piping, heat exchanger tubes |
Key Distinction: ASTM B425, B424, and B423 form a complementary family of specifications for Alloy 825-type materials across all product forms. B425 covers rod/bar (solid long products), B424 covers flat products (plate, sheet, strip), and B423 covers tubular products (seamless pipe and tube). All share the same UNS grades and similar chemical/mechanical requirements.
10. Related Standards
| Standard |
Scope |
Relationship to B425 |
| ASTM B424 |
Ni-Fe-Cr-Mo-Cu Alloy Plate, Sheet, Strip |
Flat product companion specification (same UNS grades) |
| ASTM B423 |
Ni-Fe-Cr-Mo-Cu Alloy Seamless Pipe & Tube |
Tubular product companion specification |
| ASTM B880 |
General Requirements for Nickel Alloys |
Governs tolerances, testing, certification |
| ASTM E8 / E8M |
Tension Testing of Metallic Materials |
Tensile test method required by B425 |
| ASTM E1473 |
Chemical Analysis of Ni & Ni Alloys |
Chemical analysis method for heat/product verification |
| ASTM A262 |
Intergranular Corrosion Testing |
Supplementary requirement for sensitization testing |
| ASME SB-425 |
BPVC Section II Part B |
ASME adoption; same material + CMTR + authorized inspection |
| DIN EN 10204 |
Metallic Products — Types of Inspection Documents |
3.1 CMTR certification standard |
11. How to Order — Required Information
| No. |
Item |
Requirement / Example |
| 1 |
Specification |
ASTM B425 / ASME SB-425 |
| 2 |
Grade / UNS |
e.g., UNS N08825 (Alloy 825) or UNS N08221 |
| 3 |
Shape |
Round, Square, Hexagon, Rectangle |
| 4 |
Processing |
Hot-finished (HF) or Cold-drawn (CD) |
| 5 |
Diameter / Size |
e.g., 50 mm round or 2 in. hexagon (AF) |
| 6 |
Length |
Random (RL ~3–6 m) or Cut-to-length |
| 7 |
Condition |
Annealed (default); specify if cold-worked required |
| 8 |
Supplementary Tests |
PMI, A262 IGC, UT, impact testing |
| 9 |
Certification |
EN 10204 3.1 Certified Mill Test Report |
| 10 |
Quantity |
Pieces or total weight (kg / metric tons) |
Download ASTM B425 / B425M Standard (PDF)
The official ASTM B425/B425M-26 PDF is available from our HT Pipe Download Center. The document includes full chemical composition Table 1, mechanical property Table 2, heat treatment requirements, dimensions and tolerances (Tables 3–7), testing methods, and supplementary requirements.
Go to Download Center | Request MTC / Quotation
12. Frequently Asked Questions
Q: What is ASTM B425 nickel alloy rod?
ASTM B425/B425M is the standard specification for nickel-iron-chromium-molybdenum-copper alloys in the form of hot-finished and cold-drawn rod, bar, and shapes (rounds, squares, hexagons, rectangles). It covers UNS N08825 (Alloy 825), UNS N08221, UNS N06845, and UNS N08827. The most widely used grade is UNS N08825, commercially known as Alloy 825 or Incoloy 825.
Q: What is Alloy 825 (UNS N08825)?
Alloy 825 (UNS N08825) is an austenitic nickel-iron-chromium alloy with additions of molybdenum (2.5–3.5%), copper (1.5–3.0%), and titanium (0.6–1.2%). It was developed to provide exceptional resistance to both oxidizing and reducing acids, chloride stress corrosion cracking, pitting, and crevice corrosion. The titanium addition stabilizes the alloy against sensitization during welding.
Q: What are the mechanical properties of Alloy 825 rod per ASTM B425?
In the annealed condition, UNS N08825 (Alloy 825) rod and bar must meet: minimum tensile strength 586 MPa (85 ksi), minimum yield strength 0.2% offset 241 MPa (35 ksi), minimum elongation 30% in 50 mm (2 in.), and maximum hardness 200 HB.
Q: What is the difference between UNS N08825 and UNS N08221?
Both are nickel-iron-chromium-molybdenum-copper alloys covered by ASTM B425. UNS N08825 (Alloy 825) has 2.5–3.5% Mo and 19.5–23.5% Cr. UNS N08221 has higher molybdenum content (5.0–6.5% Mo), narrower chromium range (20–22%), lower carbon limit (0.025% max vs 0.05%), and tighter silicon control (0.050% max vs 0.50%). N08221 offers superior pitting and crevice corrosion resistance in aggressive chloride environments.
Q: What is the difference between ASTM B425 and ASTM B424?
ASTM B425 covers nickel-iron-chromium-molybdenum-copper alloy rod, bar, and shapes. ASTM B424 covers the same alloy family in plate, sheet, and strip form. Both specifications share the same UNS grades and similar chemical and mechanical requirements. B425 is for solid long products (machined parts, fasteners, shafts); B424 is for flat products (pressure vessels, heat exchangers).
Q: Is ASTM B425 the same as ASME SB-425?
Technically identical in chemistry and mechanical properties. ASME SB-425 is ASTM B425 adopted into ASME BPVC Section II Part B. SB-425 additionally requires Certified Material Test Reports (CMTR) with full traceability and authorized inspection for ASME Code-stamped equipment. Most mills supply dual-certified B425/SB-425 material.
Request a Quote — ASTM B425 Nickel Alloy Rod & Bar
Zhengzhou Huitong (HT Pipe) supplies ASTM B425 / SB-425 compliant nickel alloy rods and bars in UNS N08825, UNS N08221, and other grades. Full EN 10204 3.1 CMTRs and competitive lead times from affiliated mills.
