How to choose high temperature pipe materials? Comparison of chemical composition, mechanical properties and applicability between ASTM A106 Gr.B and API 5L Gr.B

In industries such as petrochemicals, electric power, boilers and pressure vessels, the choice of high-temperature pipeline materials directly affects the safety, reliability and service life of equipment. ASTM A106 Gr.B and API 5L Gr.B are two widely used carbon steel seamless pipe standards, but their application scenarios and performance characteristics are significantly different. This article will compare and analyze the chemical composition, mechanical properties, applicable temperature range, main uses, etc. to help engineers and purchasers make more reasonable material selection decisions.

1. Standard Overview and Main Applications
Standard ASTM A106 Gr.B API 5L Gr.B
Scope of application High-temperature and high-pressure pipelines (boilers, thermal systems, petrochemicals) Oil and natural gas transportation (long-distance pipelines, gathering pipelines)
Manufacturing process Seamless steel pipe (Seamless) Seamless steel pipe (Seamless) or welded steel pipe (Welded)
Typical applications Steam pipelines, high-temperature process pipelines Oil and gas transportation, low-pressure fluid transportation
Key differences:

ASTM A106 Gr.B is designed for high-temperature and high-pressure conditions and is suitable for steam, superheated hot water and high-temperature oil transportation.

API 5L Gr.B is mainly for oil and gas transportation, focusing more on welding performance and low-temperature toughness rather than long-term high-temperature stability.

2. Chemical composition comparison (%)

Element ASTM A106 Gr.B API 5L Gr.B Impact analysis

C (carbon) ≤0.30 ≤0.28 A106 has a slightly higher carbon content, which improves high-temperature strength but reduces weldability

Mn (manganese) 0.29-1.06 0.90-1.20 API 5L has a higher Mn content, which enhances low-temperature impact toughness

P (phosphorus) ≤0.035 ≤0.025 API 5L has a lower P content, which reduces the risk of cold brittleness

S (sulfur) ≤0.035 ≤0.015 API 5L has a lower S content, which improves welding quality

Si (silicon) ≥0.10 ≥0.10 Similar, improves heat resistance

Conclusion:

API 5L Gr.B has stricter restrictions on P and S content, which is suitable for welding and low-temperature environments.

ASTM A106 Gr.B allows slightly higher C and Mn to enhance high temperature strength, but attention should be paid to preheating during welding.

3. Comparison of mechanical properties
Performance ASTM A106 Gr.B API 5L Gr.B Differences
Tensile strength (MPa) ≥415 ≥414 Basically equivalent
Yield strength (MPa) ≥240 ≥241 Basically equivalent
Elongation (%) ≥30 ≥30 Same
Impact test Usually not required May be required (such as low temperature environment) API 5L pays more attention to low temperature toughness
High temperature performance comparison:

ASTM A106 Gr.B maintains good strength for long-term use below 425°C, suitable for boilers and thermal pipelines.

API 5L Gr.B has no clear high temperature performance requirements, and long-term high temperature use may lead to a decrease in strength.

4. Applicable temperature range
Material Recommended temperature range Restrictions
ASTM A106 Gr.B -29°C to 425°C Alloy steel should be considered above 425°C
API 5L Gr.B -20°C to 200°C Strength decays rapidly at high temperatures
Key points:
ASTM A106 Gr.B is the first choice for high-temperature pipelines, such as steam systems and hot oil pipelines.
API 5L Gr.B is suitable for normal or low-temperature oil and gas transportation, and high-temperature conditions need to be carefully evaluated.

5. Material selection recommendations
When choosing ASTM A106 Gr.B
✅ High temperature conditions (>200°C, such as boilers, heat exchangers)
✅ High-pressure steam or hot oil pipelines
✅ Long-term high-temperature stability required

When choosing API 5L Gr.B
✅ Oil and natural gas pipelines
✅ Low-temperature environment (impact test required)
✅ Projects with high welding requirements

6. Conclusion
High-temperature and high-pressure pipelines (such as power plants, petrochemical plants) → ASTM A106 Gr.B (better high-temperature performance)

Oil and gas pipelines (such as long-distance pipelines, gathering and transportation systems) → API 5L Gr.B (better weldability and low-temperature toughness)

If the project involves high temperature + welding requirements at the same time, a comprehensive assessment is required, and preheating or post-weld heat treatment is used if necessary to ensure safety.