1. Optimization of Material Selection
Low-temperature environment: Prioritize materials with excellent low-temperature toughness (such as L245NS, X80Q, or Q345E), requiring a Charpy V-notch impact energy of ≥60J (tested at -60℃).
Corrosive environment: 304L/316L stainless steel can avoid the risk of low-temperature brittle fracture in ordinary carbon steel.
Composition control: Limit the content of carbon equivalent (Ceq≤0.42%), sulfur (S≤0.020%), and phosphorus (P≤0.025%) to reduce the tendency for cold brittleness.
2. Improvement of Manufacturing Process
Controlled rolling and controlled cooling (TMCP): Refine the grain size to ASTM grade 10 or higher to improve toughness.
Heat treatment process: Normalizing treatment combined with microalloying (such as adding vanadium and niobium) to stabilize the microstructure.
Welding control: Use low-hydrogen welding materials to avoid degradation of toughness in the heat-affected zone.
3. Design and Usage Specifications
Avoidance of stress concentration: Use rounded transitions in the design to avoid sharp notches or overlapping welds.
Thermal insulation measures: Low-temperature pipelines require a thickened insulation layer (≥3 times the pipe thickness) to prevent damage from freezing.
Load management: Avoid exceeding the design load or frequent alternating stresses to reduce the risk of fatigue cracks.
4. Inspection and Maintenance
Non-destructive testing: Regularly perform ultrasonic testing (UT) or magnetic particle testing (MT) to check for internal cracks.
Impact testing: Require suppliers to provide impact energy reports under -40℃ conditions (≥34J).
Maintenance system: Establish a defect monitoring mechanism and replace damaged components promptly.
