铝合金深腔超薄箱底超低温净成形及性能调控

doi:10.3901/JME.2025.14.036

摘要/Abstract

摘要： 铝合金是运载火箭的主体结构材料，箱底受力最复杂，是箭体结构制造的“皇冠”。铝合金超薄箱底整体成形起皱和开裂缺陷并存，始终是未得到实质性突破的国际难题。为此，以运载火箭燃料贮箱2250整体箱底为研究对象，通过数值模拟阐明超薄箱底整体成形应力应变演变规律；针对传统技术存在易开裂、起皱和组织性能难调控的挑战，基于固溶态铝合金在超低温条件下延伸率与硬化同时提高的“双增效应”，提出薄壁结构超低温成形应力与性能协同调控原理，通过超低温梯度冷却调控应力分布，降低开裂风险，提高位错与亚结构密度，实现箱底变形均匀性与性能调控；研发出铝合金薄壁构件超低温成形装备，平台尺寸3 m、最大成形力22 MN、最低温度-190 ℃，具备全尺寸构件研发与制造能力；开展新一代运载火箭整体超薄箱底超低温成形工艺研究，采用初始壁厚4.0 mm的薄板直接成形出直径2 250 mm的贮箱整体箱底，厚径比突破至1.4‰，壁厚均差率仅为6.5%，力学性能达到2219铝合金T8态强化水平以上，并且构件尺寸一致性好、椭圆度小于0.5‰。超低温成形整体超薄箱底，成形后不再加工、直接使用，在国际上率先实现火箭贮箱箱底整体净成形，为大尺寸铝合金超薄构件整体成形提供全新技术途径。

关键词: 铝合金, 整体超薄箱底, “双增效应”, 超低温成形, 净成形

Abstract: Aluminum alloys are the main structural materials used in launch vehicles. The rocket tank dome is subjected to complex stresses during service, which is known as the "crown" in the manufacturing of rocket structures. Wrinkling and splitting occur simultaneously in the integrated forming of aluminum alloy ultra-thin domes, which is an international problem that has not been substantively solved. Therefore, the integral tank dome with a diameter of 2250 mm was selected as the research subject, and its evolution of stress and strain in the integrated forming process was analyzed through simulation. To solve the challenges of traditional forming technologies such as splitting, wrinkling, and difficulty in controlling microstructure and properties, the principle of cryogenic forming for the aluminum alloy ultra-thin dome was proposed based on the “dual enhancement effect” of W-temper aluminum alloys, which refers to the simultaneous enhancement of ductility and strain hardening ability at cryogenic temperatures. The stress distribution is controlled through cryogenic temperature gradient cooling, reducing the splitting risk in unsupported region and improving densities of the dislocation and substructures, leading to the better deformation uniformity and performance distribution. The world’s first ultra-low temperature forming press was developed with 22 MN in drawing force, 3 m in platform dimension, and -190 ℃ in lowest temperature. This equipment has the full-scale research and forming capabilities for the components up to 2 m in diameter. The research on cryogenic forming process was conducted for the integral dome of the new generation launch vehicle. An integral dome with a diameter of 2250 mm was directly formed successfully through a thin sheet with an initial wall thickness of 4.0 mm. The thickness-to-diameter ratio was further improved to 0.14%. And its thickness distribution was very uniform, with an average deviation rate of only 6.5%. The mechanical properties of cryogenic forming integral ultra-thin dome could achieve the strengthening level of 2219 aluminum alloy in T8-temper. The high dimensional consistency of cryogenic formed domes could be also obtained and the ellipticity could be less than 0.05%. The integral ultra-thin dome formed through cryogenic forming can be used directly without post-forming machining, which was the first time to achieve the net-shape forming of the launch vehicle dome. Cryogenic forming offers a new approach for the integrated forming of large-size ultra-thin components made from aluminum alloys.

Key words: aluminum alloy, integral ultra-thin dome, dual enhancement effect, cryogenic forming, net-shape forming

中图分类号:

TG389

凡晓波, 杨光, 邬方兴, 关阳. 铝合金深腔超薄箱底超低温净成形及性能调控[J]. 机械工程学报, 2025, 61(14): 36-44.

FAN Xiaobo, YANG Guang, WU Fangxing, GUAN Yang. Net-shape Cryogenic Forming of Deep Cavity Ultra-thin Aluminum Alloy Dome and Its Performance Control[J]. Journal of Mechanical Engineering, 2025, 61(14): 36-44.

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