A106 vs A333: Temperature Service Range
ASTM A106 and ASTM A333 are both seamless carbon and low-alloy steel pipe specifications, but they serve fundamentally different temperature ranges. A106 covers high-temperature service (up to ~427°C). A333 covers low-temperature service (down to -196°C), with mandatory Charpy V-notch impact testing to guarantee toughness at sub-zero temperatures.
Quick Answer
Use ASTM A106 Grade B for standard and elevated-temperature piping (ambient to 427°C). Use ASTM A333 Grade 6 for low-temperature service (down to -46°C) or Grade 3 (down to -101°C). The specifications are not interchangeable: A106 does not guarantee impact toughness at low temperatures, and A333 is not intended for high-temperature service.
Detailed Comparison
Temperature Coverage
ASTM A106 is designed for piping that operates at ambient and elevated temperatures. It has no mandatory low-temperature impact testing requirement (unless supplementary requirements are invoked). The design code (ASME B31.3) typically limits A106 Gr.B to a minimum design temperature of -29°C without impact testing, based on the material’s inherent toughness.
ASTM A333 is specifically designed for piping at cryogenic and low temperatures. Every heat of A333 pipe must pass Charpy V-notch impact testing at the minimum specified temperature for the grade. This makes it the mandatory specification for LNG terminals, cold boxes, refrigeration systems, and any service below the impact-test exemption limits of A106.
Comparison Table
| Property | A106 Grade B | A333 Grade 6 | A333 Grade 3 |
|---|---|---|---|
| Service | Elevated temperature | Low temperature | Cryogenic |
| Min design temp | -29°C (-20°F) typical | -46°C (-50°F) | -101°C (-150°F) |
| Max design temp | 427°C (800°F) | ~343°C (650°F) | ~343°C (650°F) |
| Carbon (max) | 0.30% | 0.30% | 0.19% |
| Manganese | 0.29-1.06% | 0.29-1.06% | 0.31-0.64% |
| Nickel | - | - | 3.18-3.82% |
| Tensile strength (min) | 415 MPa (60 ksi) | 415 MPa (60 ksi) | 450 MPa (65 ksi) |
| Yield strength (min) | 240 MPa (35 ksi) | 240 MPa (35 ksi) | 240 MPa (35 ksi) |
| Charpy impact test | Not mandatory | Mandatory at -46°C | Mandatory at -101°C |
| Impact requirement | - | 18 J (13 ft-lbs) min avg | 18 J (13 ft-lbs) min avg |
| Heat treatment | Hot finished or normalized | Normalized or QT | Normalized or QT |
| Matching fitting | A234 WPB | A420 WPL6 | A420 WPL3 |
| Matching forging | A105 | A350 LF2 | A350 LF3 |
| Relative cost | Baseline | 15-25% premium | 40-60% premium (Ni content) |
Grade Selection Guide
| Minimum Design Temperature | Recommended Specification |
|---|---|
| Above -29°C (standard) | A106 Gr.B |
| -29°C to -46°C | A333 Gr.6 |
| -46°C to -101°C | A333 Gr.3 (3.5% Ni) |
| Below -101°C (LNG, nitrogen) | A333 Gr.8 (9% Ni) or stainless steel |
Matching Components
When A333 pipe is specified, all matching components must also be rated for low-temperature service:
- Fittings: ASTM A420 (WPL6, WPL3) instead of A234 WPB
- Forgings/flanges: ASTM A350 (LF2, LF3) instead of A105
- Bolting: ASTM A320 L7 instead of A193 B7
This ensures the entire piping system has verified toughness at the design temperature.
For full specifications on carbon steel piping materials, see the dedicated guide.
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