ASTM A333 Gr.6 and Gr.8 are seamless and welded steel pipes for low temperature use produced in accordance with the American Society for Testing and Materials (ASTM) A333 standards. These steel pipes are mainly used to transport liquids such as liquefied petroleum gas (LPG), liquefied natural gas (LNG) and other cryogenic fluids under cryogenic conditions (-45°C to -150°C).
The ASTM A333 standard specifies the requirements for steel pipe size, shape, weight, material properties, manufacturing methods, inspection and testing. Among them, Gr.6 and Gr.8 are two different material grades specified in the standard. Gr.6 is typically manufactured from low-alloy steel with high yield and tensile strength, making it suitable for lower temperature applications. Gr.8, on the other hand, uses a higher alloy content, has better low-temperature toughness and impact resistance, and is suitable for applications at lower temperatures.
ASTM A333/A 333M Chemical Composition (%):
| A333/A 333M | Chemical Components (%) | |||||
| Grade | C | Si | Mn | P | S | Ni |
| GR.1 | 0.30max | … | 0.40-1.06 | 0.025max | 0.025max | … |
| GR.6 | 0.30max | 0.10min | 0.29-1.06 | 0.025max | 0.025max | … |
| GR.8 | 0.13max | 0.13-0.32 | 0.90max | 0.025max | 0.025max | 8.40-9.60 |
ASTM A333/A 333M Tensile Requirements
| A333/A 333M | Grade 1 | Grade 6 | Grade 8 | |||
| psi | Mpa | psi | Mpa | psi | Mpa | |
| Tensile strength, min | 55000 | 380 | 60000 | 415 | 100000 | 690 |
| Yield strength, min | 30000 | 205 | 35000 | 240 | 75000 | 515 |
| Longitudinal | Trans- verse |
Longitudinal | Trans- verse |
Longitudinal | Trans- verse |
|
| Elongation, min | 35 | 25 | 30 | 16.5 | 22 | … |
