What key factors should be considered when choosing seamless steel pipes?
Use environment: high temperature, high pressure, corrosive media, etc.
Mechanical properties: tensile strength, yield strength, impact toughness, etc.
Dimensions: outer diameter, wall thickness, length and tolerance requirements.
Material requirements: carbon steel (such as 20#, 45#), alloy steel (such as 16Mn), stainless steel (such as 304, 316).
Implementation standards: such as GB/T 8163 (fluid transportation), API 5L (petroleum pipeline), ASTM A106 (high temperature).
How to choose the material of seamless steel pipe according to the purpose?
General structure: carbon steel (such as 20#, Q345), suitable for mechanical structure and building support.
High pressure/high temperature: alloy steel (such as 15CrMo, P91), used for boilers and petrochemical pipelines.
Corrosion-resistant environment: stainless steel (such as 304, 316L), suitable for chemical industry and marine engineering.
Low temperature environment: Low temperature carbon steel (such as ASTM A333 Gr.6) is used for LNG pipelines.
How do the size specifications of seamless steel pipes affect the selection?
Outer diameter and wall thickness:
High-pressure pipelines require thick-walled pipes (such as SCH80, SCH160).
Standard wall thickness (such as SCH40) is commonly used for fluid transportation.
Length: Fixed length (such as 6m, 12m) reduces welding joints and is suitable for long-distance pipelines.
Unfixed length is suitable for short-distance or non-standard equipment.
Tolerance control: Precision machinery pipes require strict dimensional tolerances (such as ±0.1mm).
What are the differences between the standards of seamless steel pipes (such as GB, ASTM, API)? How to choose?
GB/T (national standard): GB/T 8162 (structural use), GB/T 8163 (fluid transportation).
Applicable to general domestic industrial fields.
ASTM (American standard): ASTM A106 (high temperature use), ASTM A53 (general purpose).
Commonly used for export or international projects.
API 5L: For oil and gas industry only, divided into PSL1 (normal) and PSL2 (high requirements).
Selection basis: Determined according to project contract, industry specifications or customer requirements.
How to verify whether the quality of seamless steel pipe meets the requirements?
Document verification: Quality certificate (MTC), chemical composition report, mechanical properties test report.
Inspection method: Non-destructive testing: Ultrasonic (UT), radiography (RT) to check internal defects.
Dimension detection: Caliper, micrometer to measure wall thickness/outer diameter.
Pressure test: Water pressure/air pressure test for sealing and pressure bearing capacity.
Third-party certification: Inspection by SGS, BV and other institutions to ensure compliance with international standards.
