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Table of Contents
Inconel 625 is governed by a family of ASTM specifications that define everything from chemical composition to mechanical testing. Selecting, ordering, and certifying Inconel 625 material requires knowing exactly which ASTM standard applies to each product form. This guide covers every relevant standard—with scope, key requirements, and practical specification guidance.
ASTM International develops the material specifications that define the chemical composition, mechanical properties, heat treatment, dimensional tolerances, and testing requirements for Inconel 625 across all product forms. When you order "Inconel 625 pipe," the ASTM standard is what transforms that informal description into a legally binding, inspectable, and certifiable specification.
Without the correct ASTM standard on your purchase order, you have no contractual basis for rejecting non-conforming material. A supplier could deliver pipe with lower yield strength, improper heat treatment, or out-of-tolerance dimensions—and you would have no recourse. ASTM standards close this gap by providing a universally accepted reference that both buyer and supplier can verify against.
This guide covers ten primary ASTM standards that directly specify Inconel 625 products, plus seven supporting testing standards referenced within them. For each, we explain the scope, key requirements, and how to use it in practice.
Quick Navigation
Product Standards: B443 (plate/sheet) · B444 (seamless pipe) · B446 (bar/rod) · B564 (forgings) · B704 (welded tube) · B705 (welded pipe) · B366 (fittings) · B829/B751/B775 (general requirements) · F467/F468 (fasteners)
Testing Standards: E8, E1473, E18, G28, E213, E112, E1476
Related: ASTM vs ASME · AMS Specifications · NACE MR0175
The table below provides a quick-reference summary of all ASTM standards governing Inconel 625 products. Each standard is explained in detail in the sections that follow.
ASTM Standard | Product Form | UNS | Grades Covered | ASME Equivalent |
|---|---|---|---|---|
B443 | Plate, Sheet, Strip | N06625 | Grade 1 & Grade 2 | SB-443 |
B444 | Seamless Pipe & Tube | N06625 | Grade 1 & Grade 2 | SB-444 |
B446 | Bar & Rod | N06625 | Grade 1 & Grade 2 | SB-446 |
B564 | Forgings (all nickel alloys) | N06625 + others | As specified | SB-564 |
B704 | Welded Tube | N06625 | Grade 1 | SB-704 |
B705 | Welded Pipe | N06625 | Grade 1 | SB-705 |
B366 | Wrought Welded Fittings | N06625 + others | As specified | SB-366 |
B829 | General Requirements (Seamless) | N06625 + others | — | SB-829 |
B751 | General Requirements (Welded Tube) | N06625 + others | — | SB-751 |
B775 | General Requirements (Welded Pipe) | N06625 + others | — | SB-775 |
F467 | Nonferrous Nuts | N06625 | As specified | — |
F468 | Nonferrous Bolts & Studs | N06625 | As specified | — |
Plate, Sheet, and Strip
Full title: Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625) and Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219) Plate, Sheet, and Strip
ASTM B443 is the governing specification for all flat-rolled Inconel 625 products. It covers material from thin strip (0.05 mm) through heavy plate (up to 100 mm or thicker). This standard is referenced when ordering Inconel 625 plate for pressure vessel fabrication, sheet for heat exchanger manufacturing, or strip for cladding and overlay applications.
Key Requirements per ASTM B443
Chemical composition: Must conform to UNS N06625 limits (Ni 58% min, Cr 20-23%, Mo 8-10%, Nb+Ta 3.15-4.15%, Fe 5% max, C 0.10% max)
Heat treatment: Grade 1 solution annealed at 1095-1205°C (2000-2200°F), rapid cooled; Grade 2 additionally aged at ~730°C for 8-10 hours
Tensile strength: Minimum 827 MPa (120 ksi) for both grades
Yield strength (0.2% offset): Grade 1 minimum 414 MPa (60 ksi); Grade 2 minimum 655 MPa (95 ksi) for plate over 12.5 mm
Elongation in 50 mm: Minimum 30% for Grade 1; minimum 18% for Grade 2
Dimensional tolerances: Per ASTM B443 Tables 3-7, varying by thickness and width
For a detailed breakdown of the chemical composition behind these requirements, see our Inconel 625 Chemical Composition reference page.
Seamless Pipe and Tube
Full title: Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625) and Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219) Seamless Pipe and Tube
ASTM B444 is the most critical standard for Inconel 625 piping applications. It covers seamless pipe and tube manufactured by extrusion or piercing from a solid billet—with no longitudinal weld seam. This is the standard specified for high-pressure process piping, subsea flowlines, downhole tubing, and ASME Section VIII pressure vessel applications.
Key Requirements per ASTM B444
Manufacturing process: Seamless only (extruded or pilgered)
Size range: Typically 1/4" to 8" NPS; outside diameter 6 mm to 219 mm
Grades: Grade 1 (solution annealed) and Grade 2 (annealed + aged)
Heat treatment: Full solution anneal at 1095°C minimum; sections over 50 mm require water quench to avoid sensitization
Mechanical properties: Tensile 827 MPa min, yield 414 MPa min (Grade 1); elongation 30% min
Hydrostatic test: Required at 1.5x design pressure or per ASME B31.3, unless non-destructive examination (NDE) is substituted
NDE: Ultrasonic examination per ASTM E213 may be specified for critical service
General requirements: B444 references ASTM B829 for general requirements (dimensions, tolerances, sampling, rejection)
Practical Tip
When ordering seamless Inconel 625 pipe, the complete specification should read: "UNS N06625, ASTM B444, Grade 1, [size] NPS SCH [schedule], [end type], [length], per B829 general requirements." The Grade designation is essential—without it, the supplier may default to whichever grade is available.
Bar and Rod
Full title: Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625) Rod and Bar
ASTM B446 covers Inconel 625 in bar and rod form—round, square, hexagonal, and rectangular cross-sections. This standard is the procurement specification for bar stock used to manufacture machined components such as valve stems, pump shafts, fasteners, flanges, and wellhead components.
Key Requirements per ASTM B446
Forms: Hot-worked and cold-worked; round, square, hexagonal bar
Condition: Grade 1 (solution annealed) is standard; Grade 2 (aged) available for high-strength applications
Surface finish: Hot-rolled, cold-drawn, turned, or ground per the purchaser's specification
Mechanical properties: Same as B443 (tensile 827 MPa min, yield 414 MPa min for Grade 1)
Size tolerances: Per B446 Tables for diameter/width, with closer tolerances for cold-drawn and ground bar
Ultrasonic testing: May be specified per ASTM E213 for critical components (aerospace, nuclear)
For full property data including elevated-temperature values and cryogenic toughness, refer to the Inconel 625 Mechanical Properties reference.
Nickel Alloy Forgings
Full title: Standard Specification for Nickel Alloy Forgings
Unlike B443 and B444, which are specific to UNS N06625, ASTM B564 is a multi-alloy standard that covers forgings for all nickel alloys, including Inconel 625. The standard defines forging methods, heat treatment, testing, and certification requirements. Inconel 625 forgings are used for flanges, forged fittings, valve bodies, wellhead components, and forged rings for pressure vessel construction.
Key Requirements per ASTM B564
Applicable alloys: All nickel alloys including UNS N06625 (Inconel 625)
Forging methods: Open-die, closed-die, ring rolling, and upset forging
Heat treatment: Solution anneal at 1095°C minimum for Inconel 625; rapid cool
Hardness: Maximum 35 HRC (critical for NACE MR0175 sour service compliance)
Testing: Tensile test per ASTM E8; hardness test per ASTM E18; one test per heat or per forging lot
Non-destructive examination: Liquid penetrant (ASTM E165) or magnetic particle examination may be specified for critical forgings
Grain size: Typically ASTM No. 4 or finer for pressure vessel applications
Welded Tube
Full title: Standard Specification for Welded Alloy Tube
ASTM B704 covers welded Inconel 625 tube manufactured by forming strip into a tubular shape and welding the longitudinal seam, typically using the TIG (GTAW) or laser welding process. Welded tube is used in heat exchanger and boiler applications where the tube OD is small (typically 6-50 mm) and wall thickness is light (0.5-3 mm). The standard references ASTM B751 for general requirements.
Key Requirements per ASTM B704
Manufacturing: Autogenous TIG or laser welded from cold-rolled strip
Weld condition: As-welded or solution annealed after welding (annealed is standard for corrosion service)
Size range: Outside diameter 3.2 mm to 127 mm; wall thickness 0.25 mm to 4 mm typical
Joint factor: 1.0 if 100% radiographed and solution annealed; 0.85 without radiography
Testing: Hydrostatic or pneumatic test required; eddy current testing per ASTM E426 may be substituted
Weld inspection: Radiographic examination per ASTM E1032 may be specified for critical service
Welded Pipe
Full title: Standard Specification for Nickel-Alloy Welded Pipe
ASTM B705 covers welded Inconel 625 pipe in larger diameters than B704 tube. Welded pipe is used when seamless pipe is not available in the required size (above 8" NPS) or when cost optimization is critical for medium-pressure, non-cyclic service. The standard references ASTM B775 for general requirements.
Key Requirements per ASTM B705
Manufacturing: TIG (GTAW), SAW (submerged arc), or combination TIG+SAW from plate
Size range: 1/2" to 24"+ NPS; wall thickness SCH 5S through SCH 80S and heavier
Post-weld heat treatment: Solution anneal at 1095°C minimum required for corrosion service
Joint factor: 1.0 with 100% radiography; 0.85 with spot or no radiography
Testing: Hydrostatic test required; tensile and bend tests on weld specimens
Weld repair: Permitted with qualified procedure; repair area must be re-examined
Factory-Made Wrought Welded Fittings
Full title: Standard Specification for Factory-Made Wrought Nickel Alloy and Nickel-Chromium-Iron Alloy Welded Fittings
ASTM B366 covers factory-made butt-weld fittings in Inconel 625—elbows, tees, reducers, caps, and crosses. These fittings are used with Inconel 625 pipe to construct process piping systems per ASME B31.3. The standard defines fitting dimensions (per ASME B16.9), wall thickness matching, and weld preparation requirements.
Key Requirements per ASTM B366
Fitting types: Butt-weld elbows (45°, 90°, 180°), tees (equal and reducing), reducers (concentric and eccentric), caps, stub ends
Dimensions: Per ASME B16.9 for butt-weld fittings
Wall thickness: Must match or exceed the schedule of the pipe it connects to
Manufacturing: Formed from plate or pipe, with welded construction where required
Heat treatment: Solution annealed after forming and welding
Pressure rating: Fitting pressure rating equals that of matching pipe of the same schedule
Three ASTM standards provide the general requirements that supplement the product-specific standards above. They define the rules for dimensions, tolerances, sampling, testing frequency, rework, rejection, and certification that apply across all nickel alloy product forms.
Standard | Covers | Referenced By | Key Contents |
|---|---|---|---|
ASTM B829 | General requirements for seamless nickel alloy pipe & tube | B444 (seamless pipe/tube) | Dimensional tolerances, sampling plans, test specimen preparation, certification requirements |
ASTM B751 | General requirements for welded nickel alloy tube | B704 (welded tube) | Weld seam inspection, dimensional tolerances for welded tube, NDE requirements |
ASTM B775 | General requirements for welded nickel alloy pipe | B705 (welded pipe) | Weld seam inspection, plate-to-pipe tolerance, NDE and hydrostatic test requirements |
Why General Requirements Matter
The product standard (e.g., B444) defines what the material must be. The general requirements standard (e.g., B829) defines how it is verified, sampled, tested, and certified. A complete purchase order references both: "ASTM B444, including general requirements per ASTM B829."
Inconel 625 fasteners—bolts, studs, nuts, and threaded rod—are specified under two ASTM standards that cover nonferrous fastener materials broadly:
Standard | Product | Inconel 625 Grade | Typical Application |
|---|---|---|---|
ASTM F467 | Nonferrous nuts | UNS N06625 | Nuts matching Inconel 625 or B7/B8 studs in flanged connections |
ASTM F468 | Nonferrous bolts, studs, threaded rod | UNS N06625 | Bolting for pressure vessel flanges, heat exchanger closures, subsea connectors |
For high-strength fastener applications (yield strength above 724 MPa), consider Inconel 718 (AMS 5662/5663) instead of Inconel 625, as 718's age-hardening response provides significantly higher bolt strength.
The product standards above reference a family of testing standards that define how material properties are measured and verified. These standards ensure that test results are reproducible across different laboratories and suppliers:
ASTM Standard | Test Method | What It Measures | Referenced By |
|---|---|---|---|
E8 / E8M | Tensile testing of metallic materials | Yield strength, tensile strength, elongation, reduction of area | B443, B444, B446, B564 |
E1473 | Chemical analysis of nickel alloys | Wet chemistry and ICP verification of composition (Ni, Cr, Mo, Nb, etc.) | All product standards |
E18 | Rockwell hardness testing | Hardness (HRC, HRB); critical for NACE MR0175 compliance (max 35 HRC) | B446, B564 |
G28 | Intergranular corrosion testing | Susceptibility to intergranular attack (Method A: boiling 50% H₂SO₄ + Fe₂(SO₄)₃) | Specified for corrosion-critical service |
E213 | Ultrasonic examination of pipe & tubing | Longitudinal and transverse discontinuities in seamless/welded pipe | B444, B446 (optional for critical service) |
E112 | Grain size measurement | Austenitic grain size (ASTM No.); typically No. 4 or finer for 625 | B443, B564 (aerospace, nuclear applications) |
E1476 | Positive Material Identification (PMI) guide | Field verification of alloy grade using XRF or OES | Specified at receiving inspection |
This is one of the most common questions we receive. The distinction is straightforward but critically important for code compliance:
Aspect | ASTM | ASME |
|---|---|---|
Role | Develops material specifications | Adopts ASTM specs for pressure code use |
Designation | ASTM B444 | ASME SB-444 (adds "S" prefix) |
Differences | Base specification | May include additional requirements or revisions for code safety |
Code Construction | Not sufficient for ASME-stamped vessels | Required for ASME-stamped vessels & code piping |
Allowable Stresses | Not published | Published in ASME Section II, Part D |
When to Specify | General industrial, non-code applications | Pressure vessels, code piping, safety-critical service |
Key Rule
If your project requires an ASME code stamp (U-stamp for pressure vessels, S-stamp for boilers, PP-stamp for piping), you must specify ASME SB- prefixed materials and use allowable stresses from ASME Section II, Part D. ASTM B- prefixed material cannot be used for code-stamped construction unless it is also certified as meeting the ASME SB- requirements.
For aerospace applications, AMS (Aerospace Material Specifications), published by SAE, are used in place of or alongside ASTM standards. AMS specifications are more stringent than ASTM, with tighter composition limits, grain size requirements, and additional testing:
AMS Specification | Product Form | Key Differences from ASTM |
|---|---|---|
AMS 5599 | Sheet, strip, plate | Tighter grain size control; additional ultrasonic testing; surface quality requirements for flight-critical parts |
AMS 5666 | Bar, billet, forging | Macro-etch testing; stricter segregation limits; aerospace-grade quality assurance |
AMS 5837 | Welding wire (ERNiCrMo-3) | Controlled chemistry for filler metal; heat-lot traceability |
AMS 7000 / 7001 | Additive manufacturing powder | Specification for Inconel 625 powder for LPBF and DED 3D printing processes |
While not an ASTM standard, NACE MR0175 / ISO 15156 is essential for oil and gas applications. It defines material requirements for service in environments containing H₂S (sour gas). Inconel 625 is listed as a qualified material, but compliance must be explicitly specified and certified:
Material condition: Solution annealed (Grade 1) at 1095°C minimum
Hardness limit: Maximum 35 HRC, verified per ASTM E18
Certification: NACE compliance must be stated on the Mill Test Report (EN 10204 3.1 or 3.2)
Applicable products: All product forms (pipe, plate, bar, forgings, fittings) can be NACE-certified
Temperature range: Qualified for all temperatures per NACE MR0175 Table for nickel alloys
For more on Inconel 625's corrosion performance, see the Inconel 625 Corrosion Resistance reference.
A correctly written purchase order specification eliminates ambiguity and ensures you receive exactly what you need. Use this template for any Inconel 625 product:
Complete Purchase Order Specification
[UNS Number], [ASTM Standard], Grade [1 or 2], [Product Form & Size], [Schedule/Thickness], [End Type], [Length], [Heat Treatment], [Testing Requirements], [Certification: EN 10204 3.1/3.2], [NACE MR0175 if applicable], [General Requirements per B829/B751/B775]
Examples by Product Form
Product | Complete Specification Example |
|---|---|
Seamless Pipe | UNS N06625, ASTM B444, Grade 1, Seamless Pipe, 4" NPS SCH 80S, BE, 6m random length, solution annealed, hydrostatic tested, EN 10204 3.1, NACE MR0175, general requirements per B829 |
Welded Pipe | UNS N06625, ASTM B705, Grade 1, Welded Pipe, 12" NPS SCH 40S, BE, 6m, solution annealed after welding, 100% radiographed, EN 10204 3.1, general requirements per B775 |
Plate | UNS N06625, ASTM B443, Grade 1, Plate, 25 mm x 1500 mm x 3000 mm, solution annealed, UT tested per E213, EN 10204 3.2 |
Bar | UNS N06625, ASTM B446, Grade 1, Round Bar, 50 mm dia x 3000 mm, cold drawn & solution annealed, EN 10204 3.1, NACE MR0175 |
Forging | UNS N06625, ASTM B564, Forged Flange, Weld Neck 6" Class 300, solution annealed, hardness max 35 HRC, EN 10204 3.1, NACE MR0175 |
Fittings | UNS N06625, ASTM B366, 90° LR Elbow, 4" NPS SCH 80S, solution annealed, EN 10204 3.1 |
Common Specification Error
The most common mistake is writing "Inconel 625 pipe" without specifying the ASTM standard, grade, or schedule. This gives the supplier latitude to ship any material that matches the alloy name—potentially Grade 2 when you needed Grade 1, or welded when you needed seamless. Always use the full specification string.
What is the difference between ASTM B444 and ASTM B705?
ASTM B444 covers seamless Inconel 625 pipe and tube, manufactured by extrusion from a solid billet with no weld seam. ASTM B705 covers welded Inconel 625 pipe, manufactured by forming plate into a cylinder and welding the longitudinal seam. Seamless pipe (B444) has a joint factor of 1.0 and is required for ASME Section VIII pressure vessels and high-pressure cyclic service. Welded pipe (B705) has a joint factor of 0.85-1.0 depending on radiographic inspection level and is used for medium-pressure, non-cyclic applications and larger diameters up to 24 inches and beyond.
What is the difference between ASTM and ASME standards for Inconel 625?
ASTM develops the material specifications (e.g., ASTM B444) that define chemical composition, mechanical properties, and testing requirements. ASME adopts these specifications with minor modifications for pressure vessel and piping code use, prefixing them with "S" (e.g., ASME SB-444). Only ASME-certified materials (SB- prefix) can be used in ASME-stamped pressure vessels and code-stamped piping systems. The allowable stress values for ASME code construction are published in ASME Section II, Part D. For non-code industrial applications, ASTM specifications are sufficient.
What ASTM standard covers Inconel 625 plate and sheet?
ASTM B443 covers Inconel 625 (UNS N06625) plate, sheet, and strip. It specifies chemical composition, mechanical properties (tensile strength minimum 827 MPa, yield strength minimum 414 MPa for Grade 1, elongation minimum 30%), heat treatment requirements (solution anneal at 1095-1205°C), and permissible dimensional variations. Both Grade 1 (solution annealed) and Grade 2 (annealed + aged) conditions are covered. For aerospace applications, AMS 5599 provides a more stringent alternative specification.
What are Grade 1 and Grade 2 in ASTM standards for Inconel 625?
Grade 1 is the solution-annealed condition (1095-1205°C, rapid cooled), offering the best corrosion resistance and ductility with yield strength of 414 MPa minimum and elongation of 30% minimum. Grade 2 is solution annealed plus aged at approximately 730°C for 8-10 hours, which precipitates gamma-double-prime (Ni₃Nb) phase to increase yield strength to 620-760 MPa. Grade 2 is limited to service below 650°C because the precipitates over-age and dissolve above that temperature. Most piping, pressure vessel, and corrosion-resistant applications use Grade 1. Grade 2 is selected when higher mechanical strength is required at moderate temperatures.
Which ASTM standards apply to Inconel 625 testing and certification?
Key testing standards include ASTM E8/E8M (tensile testing), ASTM E1473 (chemical analysis of nickel alloys by ICP), ASTM E18 (Rockwell hardness testing), ASTM G28 (intergranular corrosion testing in boiling sulfuric acid/ferric sulfate), ASTM E213 (ultrasonic examination of pipe and tubing), and ASTM E112 (grain size measurement). Material certification is documented per EN 10204 Type 3.1 (manufacturer certified) or 3.2 (third-party witnessed by an independent inspection agency such as SGS, BV, or TUV). For NACE MR0175 sour service, hardness testing per ASTM E18 and compliance certification on the MTR are mandatory.
What is ASTM B829 and why is it referenced with B444?
ASTM B829 is the General Requirements specification for nickel and nickel-alloy seamless pipe and tube. It defines the rules for dimensional tolerances, sampling plans, test specimen preparation, rejection criteria, and certification documentation that supplement the product-specific standard (B444). When you order "ASTM B444," the general requirements of B829 are automatically incorporated by reference. A complete specification should state: "ASTM B444, including general requirements per ASTM B829" to ensure the supplier applies all applicable requirements.
Related Resources from the Inconel 625 Hub
→ Ultimate Guide to Inconel 625 — Complete technical reference hub
→ Inconel 625 Chemical Composition — Element-by-element analysis
→ Inconel 625 Mechanical Properties — Full property data by grade
→ Inconel 625 Corrosion Resistance — Detailed corrosion performance
→ Inconel 625 Product Page — Request a quote
We supply Inconel 625 pipe, plate, bar, forgings, and fittings with full ASTM/ASME certification, NACE MR0175 compliance, and EN 10204 3.1/3.2 MTRs. Tell us your specification and we will deliver material that passes any inspection.
