For procurement managers in the global energy, nuclear, and aerospace industries, compliance is a major pain point. When design drawings specify the use of ASTM B444 (UNS N06625) standards, any documentation or metallurgical uncertainties can lead to project rejection and costly delays.
Our Procurement Challenges:
Certification Gap:Suppliers provide materials without a verified EN 10204 3.1 Material Testing Certificate (MTC).
Hidden Internal Defects:Inferior pipes cannot pass on-site hydrostatic or ultrasonic testing.
Traceability Risks:Lack of furnace number tracking from raw material smelting to final shipment.
At Gnee Alloy, we eliminate your compliance anxieties. As a professional Tier-1 manufacturer, we offer certified Inconel 625 seamless steel pipe designed to ensure overall structural integrity.
Inconel 625 International Standard Equivalent Material and Key Differences
| Standard Body | Standard No. | Material Designation | Main Differences from ASTM B444 |
|---|---|---|---|
| ASTM | B444 / ASME SB444 | UNS N06625 (Grade 1/2) | Reference standard |
| ISO | ISO 6207 | NiCr22Mo9Nb | Slightly narrower chemical composition range |
| EN / DIN | DIN 17751 | 2.4856 | Stricter S, P limits (S ≤ 0.005% optional) |
| China GB/T | GB/T 3625 | GH3625 | Impact test requirements may differ |
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ASTM B444 UNS N06625 Inconel 625 Steel Pipe Guide
ASTM B444 UNS N06625 Inconel 625 Steel Pipe Guide
ASTM B444 is a specific standard specification for cold-worked seamless tubing made of a nickel-chromium-molybdenum-niobium alloy (UNS N06625). This material is known globally as Inconel 625. Unlike multiple alloy specifications such as ASTM B622, B444 covers only one alloy: Inconel 625. This focus on a single alloy implies stricter quality requirements, specific heat treatment processes, and mechanical property standards tailored to the unique combination of high strength, corrosion resistance, and fatigue life of Inconel 625.
What is ASTM B444 UNS N06625 material?
ASTM B444 UNS N06625 Grade 1 steel pipe is supplied in the annealed condition, while Grade 2 steel pipe is supplied in the solution-annealed condition. 2.4856 Alloy 625 steel pipe (also known as UNS N06625) possesses many superior properties. One of the most critical properties is its corrosion resistance.
1. Overview of ASTM B444 Inconel 625 Specification
| Parameter | Description |
|---|---|
| Specification | ASTM B444 / ASME SB444 |
| Material | Inconel 625 (UNS N06625) |
| Chinese Equivalent | GH3625 |
| Product Form | Seamless Tube / Welded Tube |
| Material Type | Wrought Nickel-based Corrosion Resistant Superalloy |
| Strengthening Mechanism | Solid-solution strengthening (Mo + Nb) |
| Typical Applications | Chemical processing, marine engineering, heat exchangers, oil & gas, nuclear, aerospace |
| Maximum Service Temperature (Load-Bearing) | ~600°C |
| Maximum Service Temperature (Oxidation) | ~980°C |
2. ASTM B444 Inconel 625 Chemical Composition (wt%)
| GRADE | UNS Designation |
Standard (Pipe) |
Chemical Requirement (Max) | ||||||||||||
| C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Fe | Ti | Al | Co | |||
| Inconel 625 | N06625 | B444 | 0.10 | 0.50 | 0.015 | 0.015 | 0.50 | min 58 | 20.0-23.0 | min 8-10 | - | 5.0 | 0.4 | 1.0 | Nb+Ta:3.15-4.15 |
3. ASTM B444 Inconel 625 Room Temperature Mechanical Properties
| Property | ASTM B444 Requirement | Typical Value | Test Standard |
|---|---|---|---|
| Tensile Strength, Ultimate | ≥ 830 MPa (120 ksi) | ~900 – 950 MPa | ASTM E8 |
| Tensile Strength, Yield (0.2% Offset) | ≥ 415 MPa (60 ksi) | ~450 – 500 MPa | ASTM E8 |
| Elongation at Break | ≥ 30% | ~35-45% | ASTM E8 |
| Hardness (Rockwell B) | ≤ 96 HRB | ~90-95 HRB | ASTM E18 |
| Modulus of Elasticity | ~207 GPa (30.0 × 10⁶ psi) | - | ASTM E111 |
| Poisson's Ratio | 0.29 – 0.30 | - | - |
Click to download the Inconel 625 alloy PDF file now
4. ASTM B444 Inconel 625 Pipe Size Specifications
Standard Size Range
| OD (mm) | OD (in) | Wall Thickness (mm) | Wall Thickness (in) | Typical Application |
|---|---|---|---|---|
| 3.18 | 0.125 | 0.51 | 0.020 | Instrumentation |
| 4.76 | 0.188 | 0.71 | 0.028 | Control lines |
| 6.35 | 0.250 | 0.89 | 0.035 | Hydraulic lines |
| 6.35 | 0.250 | 1.24 | 0.049 | High pressure |
| 9.53 | 0.375 | 1.07 | 0.042 | Chemical injection |
| 12.70 | 0.500 | 1.24 | 0.049 | Subsea control |
| 15.88 | 0.625 | 1.65 | 0.065 | Main lines |
| 19.05 | 0.750 | 2.11 | 0.083 | Heavy duty |
| 25.40 | 1.000 | 2.77 | 0.109 | High pressure |
| 50.80 | 2.000 | 3.40 | 0.134 | Large diameter |
Dimensional Tolerances
| Parameter | Tolerance |
|---|---|
| OD (≤ 25.4 mm) | ±0.05 – ±0.10 mm |
| OD (25.4 – 50.8 mm) | ±0.10 – ±0.15 mm |
| OD (50.8 – 101.6 mm) | ±0.15 – ±0.30 mm |
| Wall Thickness | ±10% – ±12.5% |
| Length | ±3 mm (cut lengths) |
| Ovality | ≤ 0.5% of OD |
| Wall Concentricity | ≤ 10% of wall thickness |
| Straightness | ≤ 1.0 mm/m |
Contact us to customize Inconel 625 products to fit your project dimensions
5. Complete Mechanical Properties – ASTM B444 Grade 1 vs Grade 2
| Grade | Tensile Strength (min) | Yield Strength 0.2% (min) | Elongation (min) | Hardness (max) | Typical Heat Treatment |
|---|---|---|---|---|---|
| Grade 1 (Annealed) | ≥ 830 MPa (120 ksi) | ≥ 276 MPa (40 ksi) | ≥ 30% | ≤ 96 HRB | 940-1040°C, Water or Air Quench |
| Grade 2 (Solution + Cold Worked) | ≥ 830 MPa (120 ksi) | ≥ 415 MPa (60 ksi) | ≥ 30% | ≤ 96 HRB | Solution Annealed + Cold Worked + Stress Relief at 540-620°C |
6. ASTM B444 Inconel 625 Quality Assurance
We understand that trust is built on data. Every single meter of our High-Performance Alloy 625 tubing undergoes a rigorous testing protocol:
100% NDT (Non-Destructive Testing): Including Ultrasonic Testing (UT) and Eddy Current Testing (ET) to ensure zero internal voids.
Hydrostatic Pressure Testing: Verified safety under peak industrial operating loads.
MTC 3.1 Traceability: Full heat-analysis and mechanical property verification documented with every batch.
Melting Excellence: Produced via VIM + VAR melting for ultra-purity (P, S ≤ 0.010%).
7. Inconel 625 hydrostatic test requirements
Any pipe or tubing with an outer diameter of 1/8 inch (3 mm) or larger and a wall thickness of 0.015 inch (0.38 mm) or greater must pass a hydrostatic test. The test pressure is calculated using the following formula:
P = 2St / D
Where, P = hydrostatic test pressure (psi), St = allowable fiber stress (psi), t = minimum wall thickness (inches), D = outer diameter (inches).
The maximum test pressure is 1,000 psi (6.9 MPa). Any pipe or tubing that leaks during the test is disqualified. The allowable fiber stress values are as follows:
| Parameter | Correct Description |
|---|---|
| Calculation Formula | P = 2St / D |
| Allowable Fiber Stress (Grade 1) | 30,000 psi (207 MPa) |
| Allowable Fiber Stress (Grade 2) | 25,000 psi (172 MPa) |
| Maximum Test Pressure | No fixed upper limit – calculated per formula, with safety considerations |
| Common Agreement | Buyer and manufacturer may agree on 1.5x calculated pressure |
| Rejection Criterion | Any leakage = rejection |
The manufacturer and purchaser may agree to test at 1.5 times the calculated pressure. Hot-forming quality pipe and tube is exempt from tensile and hydrostatic requirements. It is supplied for chemical and surface inspection only.
8. Gnee Alloy has in stock Inconel 625 UNS N06625 pipes for sale
| Alloy 625 UNS N06625 ERW Pipes | Alloy 625 ASTM B444 Custom Pipes |
| ASTM B444 Inconel 625 EFW Pipes | ASTM B444 Grade 2 Hot Finished Pipes |
| B444 UNS N06625 gr.1 Inconel Pipes | Inconel Alloy 625 Cold Drawn Seamless Pipes |
| Inconel DIN NR. 2.4856 Round Pipes | UNS N06625 4 inch Pipe |
| ASTM B444 625 Inconel Round Pipes | Alloy 625 UNS N06625 Annealed Pipes |
Why Choose Gnee as Your Nickel-Based Alloy Supplier
✅️Direct Factory Price: Skip the international trading agents and secure original manufacturer rates.
✅️Short Lead Time: We stock common sizes for Fast Global Shipping (typically 5-7 business days).
✅️Industrial Durability: Our materials are specifically processed for NACE MR0175 compliance, making them safe for deep-sea oil and gas service.
✅️Flexible MOQs: We support both small-batch R&D prototypes and large-scale EPC infrastructure projects.
Gnee Alloy 625 Alloy Certificate
📦 Packaging and Shipping
All Nickel Based Alloy products are packaged using the following methods:
Wooden pallets or crates
Moisture-proof packaging
Labels with furnace number, standard, and size labels
Shipped worldwide by sea, air, or express
Gnee Alloy 625 Product Packing
Contact us for the latest export price quote for Inconel 625 Alloy
FAQ
Q1: Is GH3625 interchangeble with ASTM B444 UNS N06625?
A: Absolutely. GH3625 is the technische designation used within the Chinese national standard (GB/T) for the same metallurgical system as UNS N06625 / Inconel 625. We provide certificates proving total chemical and mechanical parity.
Q2: Does your tubing meet the requirements for high-pressure hydrogen?
A: Yes. Alloy 625 has exceptional resistance to hydrogen embrittlement due to its stable face-centered cubic (FCC) austenite matrix, making it a preferred choice for modern rocket fuel and hydrogen storage systems.
Q3: Can you produce non-standard custom IDs for instrumentation?
A: Yes. As a specialized Manufacturer, we offer precision cold-drawing to achieve custom internal diameters and specialized surface roughness for sensitive aerospace sensors.
Q4: Do you offer bulk discounts for petrochemical refinery overhauls?
A: Yes. We support large-scale energy infrastructure projects with tiered Wholesale Pricing and dedicated inventory reserves.
