Cryogenic Stainless Steel Pipe

• ​Introduction

Cryogenic stainless steel pipes are specially designed to transport fluids at extremely low temperatures (typically below -150°C). They are widely used in industries such as LNG (liquefied natural gas), aerospace, and chemical processing, where materials must maintain structural integrity and leak-proof performance in cryogenic environments.

• ​Main Functions

Low-temperature fluid transport: Safely conveying cryogens like liquid nitrogen (LN₂), liquid oxygen (LO₂), liquid natural gas (LNG), and liquid helium (LHe).

Thermal insulation support: Minimizing heat transfer from the external environment to prevent fluid vaporization or pressure buildup.

Structural stability: Withstanding thermal contraction/expansion and mechanical stress caused by extreme temperature fluctuations.

Corrosion resistance: Resisting chemical reactions with cryogens or ambient moisture to avoid material degradation.

• ​Tubing Standards

ASTM A312，ASTM A269； EN 10312，EN 10216-5； GB/T 14976，GB/T 38810.

• ​Material & Performance

Primary materials: Austenitic stainless steels dominate due to their exceptional low-temperature properties. 304, 304L, 316, and 316L are the most prevalent grades. The low-carbon variants, 304L and 316L, are particularly favored for cryogenic service as they mitigate the risk of intergranular corrosion arising from carbide precipitation. 316L, with the addition of molybdenum, exhibits enhanced corrosion resistance compared to 304 grades, especially in chloride-containing environments.​

Key performance parameters:​ Low-temperature toughness: Charpy impact energy at -196°C (liquid nitrogen temperature) typically exceeds 50J, ensuring resistance to brittle fracture.​ Tensile strength: Generally ≥515MPa at ambient temperature, with retention of adequate strength levels even at ultra-low temperatures.​ Corrosion resistance: The chromium-rich passive oxide layer on the surface provides robust protection against oxidation and chemical attack from most cryogenic media.​ Thermal expansion characteristics: Possess a balanced coefficient of thermal expansion, minimizing thermal stress when interfaced with other materials in the system.

• ​Manufacturing Process

Raw Material Selection: Choose high-quality stainless steel billets or ingots that meet the required grades and standards.​

Hot Working: Heat the billets to a certain temperature and perform processes such as piercing (for seamless tubes) or welding (for welded tubes) to form the initial tube shape.​

Cold Working: Conduct cold rolling or cold drawing to achieve precise dimensions, smooth surface finish, and improve mechanical properties.​

Heat Treatment: Carry out annealing, solution treatment, or other heat treatments to eliminate internal stress, optimize the microstructure, and enhance performance.​

Inspection and Testing: Perform non-destructive testing (such as ultrasonic testing, eddy current testing) and pressure testing to ensure the quality and performance of the tubes meet standards.​

Surface Treatment: Conduct pickling, passivation, or other surface treatments to remove oxides and impurities, forming a protective film to improve corrosion resistance.

• Specifications