Research Progress on Forming Technologies of Difficult-to-Deform Seamless Special-alloy Tubes

Difficult-to-deform seamless special alloy tubes are key components of high-end equipment in aerospace, nuclear power energy, and deep-sea engineering, and their forming technologies have long face challenges such as poor material formability, narrow process windows, and difficulty in controlling.The microstructure and properties of typical difficult-to-deform alloys-including titanium alloys, nickel-based superalloys, and austenitic stainless steels under major forming processes were systematically summarized. The applicability and the current research status in China and abroad of mainstream technical routes such as ingot casting-cogging-piercing-rolling, centrifugal casting-welding, ingot casting-cogging- extrusion, and continuous casting-piercing were analyzed. The technical status of core equipment, including heavy-duty extrusion presses, special rolling mills, and heating equipment, were summarized. Building on these analyses, the key bottlenecks constraining the development of forming technologies for difficult-to-deform seamless special alloy tubes were distilled from the perspectives of materials, processes, equipment, and the entire industrial chain. Future development directions were proposed, including optimizing material systems, building process parameter databases, strengthening the control of forming microstructure and properties, advancing short-process and compact manufacturing, and promoting the new technology of direct forming by hollow continuous casting.