1. Implementation standards
Confirm the latest version of ASTM A333/A 333M (the chemical composition of the version after 2016 is adjusted, and new element restrictions such as Cr, Ni, and Mo are added).
2. Chemical composition control
Key element limits:
C≤0.30% (low carbon ensures toughness), Mn 0.29-1.06% (adjusted with C content), P≤0.025%, S≤0.025% (strictly limit harmful elements).
The 2016 version adds upper limits for Ni, Cr, Mo, etc. (such as Ni≤0.40%), and it is necessary to check whether the warranty book is marked with carbon equivalent (CET).
Material upgrade: The new version of A333GR6 has been upgraded from C-Mn steel to low alloy steel, with better performance.
1. Mechanical properties
Tensile strength ≥415MPa, yield strength ≥240MPa, low yield strength ratio (reflecting plastic deformation ability)
Low temperature impact test:
The test temperature varies with the wall thickness (such as -45℃~-52℃), and the contract requirements must be clearly stated.
The impact energy value must meet the standard, usually requiring ≥20J (refer to ASTM A333 for details).
2. Metallographic structure
The supply state should be uniform ferrite + pearlite, with a grain size of 7~9 (coarse grains can reduce the yield strength ratio).
Preferably choose steel pipes that have been quenched + tempered (the structure is tempered troostite, and the low-temperature toughness is better).
Heat treatment process
Heat treatment records must be provided: heating ≥815℃→water quenching→tempering to ensure the uniformity of the structure.
Avoid untreated or improperly treated original state (coarse structure leads to low-temperature brittleness).
Delivery status
Usually delivered in normalized + tempered or quenched + tempered state, which needs to be specified in the contract.
1. Wall thickness and impact temperature correlation
For example: when the wall thickness is 7.62mm, the impact test temperature needs to reach -52℃ (lower than the standard -45℃).
Common spot specifications: 8-1240mm×1-200mm (SCH5S-XXS), actual demand needs to be checked.
2. Equivalent alternative material
A333GR6≈X42N/L290N/API 5L B PSL2 (line pipe), but it is necessary to confirm whether the low temperature performance is met.
Must-check documents
Material certification (MTC), heat treatment report, low temperature impact test report, non-destructive testing report (UT/RT).
After the 2016 version, the test data of the newly added alloy elements (Ni, Cr, etc.) must be included.
Third-party re-inspection
It is recommended to re-inspect key items (such as impact test, chemical composition) by sampling, especially for high-risk applications (such as LNG pipelines).
Temperature range
Designed operating temperature ≥-45℃, ultra-low temperature scenarios (such as -195℃) need to evaluate whether a higher grade (such as A333GR3/GR8) is required.
Industry application
Petrochemical (ethylene, LNG), refrigeration equipment, cryogenic pipelines, etc., need to consider additional protection (such as coating) according to the corrosiveness of the medium
Qualifications and performance
Preferentially select manufacturers with ASTM A333 production qualifications, and require supply cases for similar projects.
Be wary of traders’ “OEM” behavior and verify the original factory warranty documents.
Price and delivery time
The low-alloy version (before 2016) may have a lower price, but the performance difference is large, and the comprehensive cost performance is required.
Special specifications (such as large-diameter thick-walled pipes) may need to be customized, extending the delivery cycle.
Confusion risk: Do not confuse A333GR6 with A335GR6 (chromium-molybdenum steel for high temperature).
Old standard inventory: Confirm whether the steel pipe is produced after the 2016 version to avoid the alloy elements of the old standard products not meeting the standards.
Welding process: Low-temperature steel pipe welding requires matching welding materials (such as ENiCrMo-3), and the supplier should provide welding guidance.
Through the above points, the purchaser can systematically evaluate the compliance, performance matching and supplier reliability of the A333GR6 alloy pipe to ensure the safety and economy of the project.