Manufacturing of aerospace bi-cylindrical flame tube via integrated spinning processes

Aerospace bi-cylindrical flame tubes operate under severe thermo-mechanical loading and cyclic thermal fatigue, where welded joints are prone to stress concentration, microstructural inhomogeneity, and premature failure. To mitigate these welding-induced structural vulnerabilities, seamless manufacturing has become a critical requirement for high-reliability propulsion components. This study develops an integrated spinning process combining wedge-shovel spinning for inner cylinder formation with multi-pass conventional spinning for outer cylinder creation to manufacture seamless GH4169 superalloy flame tubes. The results show that dual-roller process reduces peak radial forces by 30%-46% and improves wall thickness uniformity compared to single-roller configurations. Microstructure characterization reveals that the inner cylinder exhibits progressive grain boundary transformation with significant refinement driven by discontinuous and continuous dynamic recrystallization mechanisms, forming strong Cube recrystallization texture. The outer cylinder remains dominated by deformed grains with limited recrystallization. The outer cylinder middle region displays grain coarsening and extremely strong deformation texture through dynamic recovery during conventional spinning. Mechanical testing reveals the inner cylinder achieves 10% tensile strength increase with enhanced ductility, while maximum hardness increases 23%. This integrated spinning technology successfully manufactures seamless bi-cylindrical flame tubes with tailored microstructures, offering a viable welding-free alternative for aerospace propulsion components.