A333 Gr 8 low temperature steel pipe
Dec 05, 2025
ASTM A333 Gr. 8 Low Temperature Steel Pipe description
A333 GR8 is a low-temperature seamless steel pipe under the ASTM standard, specifically designed for extreme cryogenic environments as low as -196°C. It belongs to the 3.5% nickel series of low-temperature alloy steels. Its "low carbon, high nickel" composition (carbon ≤0.19%, nickel ~3.5%) combined with strict normalizing heat treatment ensures exceptional toughness and resistance to brittle fracture at ultra-low temperatures.
Key mechanical properties include: tensile strength ≥415 MPa, yield strength ≥240 MPa, elongation ≥30%, and Charpy impact energy ≥20J at -46°C. It is widely used in LNG transportation, cryogenic petrochemical equipment, and polar engineering applications.
ASTM A333 Grade 8 Pipe Chemical Composition Requirements
| Chemical Composition of ASTM A333 | |
|---|---|
| Element | Grade 8, % |
| C | 0.13 |
| Mn | 0.90 |
| P | 0.025 |
| S | 0.025 |
| Si | 0.13–0.32 |
| Ni | 8.40–9.60 |
| Cr | ... |
| Cu | ... |
| Al | ... |
| V | ... |
| Cb | ... |
| Mo | ... |
| Co | ... |
Tensile Requirement
|
Grade 8 |
||
|
psi |
MPa |
|
| Tensile strength Min |
100 000 |
690 |
| Yield strength Min |
75 000 |
515 |
| Longitudinal | Transverse | |
| Elongation in 2 in or 50 mm (or 4D), min, % | ||
| Basic minimum elongation for walls 5/16 in. [8mm] and over in thickness, strip tests, and for all small sizes tested in full section. | 22 | -- |
| When 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 used | 16 | -- |
| For strip tests, a deduction for each 1/32 in [0.8 mm] decrease in wall thickness below 5/16 in [8 mm] from the basic minimum elongation of the following percentage | 1.25 | -- |
Material Performance Testing Standards
1. Chemical Composition Analysis
Verification of alloy element content compliance.
2. Mechanical Property Testing
Tensile testing (yield/tensile strength, elongation)
Impact testing (e.g., Charpy V-notch)
3. Non-Destructive Testing (NDT) Standards
Ultrasonic Testing (UT):
Detects internal defects (cracks, slag inclusions, porosity) through frequency/probe angle optimization for full-coverage scanning.
Magnetic Particle Testing (MT):
Identifies surface/near-surface cracks.
Penetrant Testing (PT):
Reveals fine surface defects (micro-cracks, pinholes) undetectable by UT/MT.
4. Dimensional & Visual Inspection
Dimensional tolerances verification
Visual inspection: Surface must be uniform, smooth, and free from cracks, laps, rust, or corrosion.
Packaging and shipping
