Fracture Mechanisms in High-Pressure Sealing Pipelines for Hydrogen Fuel Cell Vehicles and Cold Heading Process Innovations of 316L Stainless Steel

In recent years, with the rapid development of hydrogen fuel cell vehicles, hydrogen-powered ships, and industrial hydrogen energy applications, the hydrogen energy industry chain has been progressively refined. As a core component of hydrogen-powered vehicles, the reliability of high-pressure hydrogen storage systems directly determines vehicle safety and endurance. The high-pressure sealed pipelines, responsible for safely transporting hydrogen under extreme pressures of 70 MPa, must meet stringent requirements including high sealing performance, hydrogen embrittlement resistance, and long-term durability. However, approximately 1% of pipelines experience leakage failures in practical applications, revealing significant technical challenges in manufacturing and service processes. Research indicates that cracks at the cone-pipe connection are the primary cause of leakage, attributed to stress concentration from cold heading process defects and alternating loads induced by assembly misalignment. To address this, this study optimized cold heading process parameters (fillet radii R₁ =2.1 mm, R₂ =3 mm, depth L₁ =2.3 mm) using the Normalized Cockcroft & Latham ductile fracture criterion (critical damage value C = 0.431) and response surface methodology, based on 316L stainless steel mechanical property tests. Simulation results demonstrate that the optimized process reduced the maximum damage value from 0.68 to 0.11 (83.7% reduction). Experimental verification confirmed the absence of microcracks on both inner and outer walls of optimized components. This research provides a process improvement solution for automotive hydrogen storage systems, significantly enhancing part safety and stability.