ASTM A333 Grade 6 Carbon Steel Pipes
Dec 04, 2025
ASTM A333 Grade 6 Carbon Steel Seamless Pipes Description
A333 Gr.6 Low-Temperature Pipe is a seamless steel pipe for low-temperature service conforming to the ASTM A333/ASME SA333 standard. It is primarily used in petrochemical equipment (such as reactors, heat exchangers, separators), natural gas processing, and cryogenic equipment manufacturing for environments ranging from -45°C to -195°C. Common specifications include an outer diameter of 21.3–762 mm and a wall thickness of 2.0–140 mm, produced via hot-rolled, cold-drawn, or hot-expanded processes. The delivery condition requires normalization heat treatment at 900°C–930°C.
A333 Grade 6 Pipes specification
Heat Treatment Requirements for A333 Grade 6 Pipes
| Composition, % | |||
| Element | Grade 1 | Grade 3 | Grade 6 |
| Carbon, max | 0.30 | 0.19 | 0.30 |
| Manganese | 0.40 – 1.06 | 0.31 – 0.64 | 0.29 – 1.06 |
| Phosphorous, max | 0.025 | 0.025 | 0.025 |
| Sulfur, max | 0.025 | 0.025 | 0.025 |
| Silicon | - | 0.18 -0.37 | 0.10 min |
| Nickel | - | 3.18 – 3.82 |
Tensile Requirements for ASTM A333 Grade 6 Pipes
| Grade 6 | |||
| MPa | psi | MPa | |
| Tensile Strength, min | 450 | 60,000 | 415 |
| Yield Strength, min | 240 | 35,000 | 240 |
| Transverse | Longitudinal | Transverse | |
| Elongation in 2 in. or 50 mm, (or 4D), min, %: | |||
| Basic minimum elongation for walls 5/16 in. [8 mm] and over in thickness, strip tests, and for all small sizes tested in full section | 20 | 30 | 16.5 |
| When the standard round 2-in. or 50-mm gage length or proportionally smaller size test specimen with the gage length equal to 4D (4 times the diameter) is use | 14 | 22 | 12 |
| For strip tests, a deduction for each 1/32in. [0.8 mm] decrease in wall thickness below 5/16 in. [8 mm] from the basic minimum elongation of the following percentage | 1.00 | 1.50 | 1.00 |
| Elongation in 2 in. or 50 mm, min, %: | |||
A333 Gr.6 vs A106 Gr.B Comparison Table
| Parameter | ASTM A333 Gr.6 | ASTM A106 Gr.B |
|---|---|---|
| Standard Scope | -45°C Cryogenic Piping | Carbon Steel Pipe for ≤425°C |
| Key Alloy | Ni-Strengthened (Ni: 3.2–3.6%) | C-Mn Steel (C≤0.30%, Mn: 0.29–1.06%) |
| Temperature Range | -45°C ~ +50°C | -29°C ~ +425°C |
| Mechanical Focus | ≥18J @ -45°C Charpy Impact | Tensile Strength ≥415 MPa (RT) |
| Mandatory Testing | Cryogenic Charpy Impact Test | Tensile Test + Hydro Test Only |
| Failure Risk | Accelerated Oxidation >+50°C | Brittle Fracture <-29°C |
| Microstructure | Ni-Stabilized Austenite + Fine Ferrite | Ferrite + Pearlite (No LT Phase Change) |
| Applications | • LNG Secondary Pipelines (-45~-100°C) • Liquid Ammonia Spray Pipes |
• 350°C Steam Transfer • Boiler Feed Pipes • General O&G Pipelines |
| Cost Reference | ≈2.5× A106 (High Ni Cost) | Cost Baseline |
| Welding Compatibility | Requires Ni-based Electrodes (e.g., ENiCrFe-3) | Standard Carbon Steel Electrodes (e.g., E7018) |
Application Scenarios and Comparative Advantages
Liquefied Natural Gas (LNG) Pipelines:
LNG transfer at -162°C requires materials with ultra-low temperature toughness. A333 Gr.6 is commonly used for valve connecting pipes in secondary cryogenic sections (-45°C to -100°C).
Chemical Processing Equipment:
Applications such as ammonia synthesis towers and ethylene cold boxes, which must withstand dual challenges of media corrosion and cryogenic stress.
Advantages Over Similar Materials:
Compared to counterparts like A333 Gr.3, Gr.6 exhibits ≈30% better low-temperature performance due to its higher nickel content (0.40–0.70%), though at a 15–20% cost premium.
Test and inspection
Packaging and shipping
