ASTM A671 vs. ASTM A672

ASTM A671 - Standard Specification for Electric Fusion Welded Steel Pipe for Atmospheric and Lower Temperatures.

ASTM A672 - Standard Specification for Electric Fusion Welded Steel Pipe for High Pressure Service at Moderate Temperatures.

Differences between ASTM A671 and ASTM A672:

‌The main differences between ASTM A671 EFW and ASTM A672 EFW are application scenarios, temperature ranges, material properties, standard classifications, welding processes, testing requirements and size ranges‌:

‌1. Application areas‌

‌ASTM A671‌: Mainly used to manufacture electric fusion welded steel pipes for normal and low temperatures, suitable for pressure vessels (such as Class 1 to Class 3 pressure vessels) and structural parts. ‌‌Such as cryogenic liquefied gas (LNG), cryogenic chemical pipelines, etc.‌

ASTM A672‌: Designed for medium-temperature and high-pressure transportation, it is widely used in pipelines for fluid media such as oil and natural gas, emphasizing high efficiency and durability. ‌‌Such as power plant steam pipelines, petrochemical pipelines, etc.

2. Applicable temperature range
‌ASTM A671: Applicable to normal and low temperature environments (minimum -50°F/-45°C)
‌ASTM A672: Applicable to medium temperature environments (-20°F to 800°F/-29°C to 427°C)

3. Material properties‌
‌ASTM A671‌:
The material is pressure vessel quality steel plate, which needs to be heat treated to improve mechanical properties (such as yield strength up to 60ksi). ‌‌
Applicable to complex working conditions (such as high pressure and low temperature environment), but the specific version (such as A671CB) needs to be selected according to the application scenario. ‌‌

‌ASTM A672‌:
The material is made by electric fusion welding process, with high weld quality and stable strength, suitable for low fluid resistance and high efficiency transportation needs. ‌‌
Specifications can be customized (such as wide range of outer diameter and wall thickness), and the cross-sectional shape is a round tube to optimize fluid flow efficiency. ‌‌

4. Standard classification:
‌ASTM A671‌: The standard covers different versions (such as A and B), corresponding to different mechanical performance requirements. ‌‌
‌ASTM A672‌: There is no similar classification, but a unified technical specification is formulated according to the application scenario (such as oil and natural gas). ‌‌

The material grade representation method is different:
A671: "CL+number" is used (such as CL22, CL32)
A672: "Letter+number" is used (such as B60, C70)

The corresponding basic material standards are different:
A671: Mainly corresponds to A516 and other low-temperature steel plates
A672: Corresponds to A285 (A series), A515 (B series), A516 (C series) steel plates

5. Welding process and testing requirements
‌ASTM A671: More emphasis on low-temperature toughness, and stricter requirements on welding process requirements and low-temperature impact tests.
‌ASTM A672: More emphasis on medium-temperature strength performance.

6. Typical size range
Both are suitable for large-diameter pipes (≥16 inches)
A672 has a wider wall thickness range (up to 3 inches)

Selection suggestions:

A671 is preferred for low-temperature conditions (such as LNG)
A672 is preferred for medium-temperature and high-pressure conditions (such as power plant steam)
ASTM A691 should be considered for high-temperature conditions (＞427°C)

In summary, the core difference between the two lies in the application scenarios and material design - A671 focuses on the high-strength requirements of pressure vessels and structural parts, while A672 focuses on the efficiency and durability of fluid transportation.

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