厚大断面球墨铸铁在凝固过程中，因中心区域冷却速度缓慢，易导致石墨球数量减少、碎块状石墨及缩孔 缺陷的形成，显著削弱其力学性能。为解决这一问题，提出一种新型胶囊缓释孕育工艺，通过胶囊缓释孕育，延缓孕育剂 释放优化石墨形态和增加石墨数量。 采用包内冲入球化孕育和缓释孕育复合工艺制备三组试样(HDQT-0、HDQT-0.1、 HDQT-0.3)，对比分析了孕育方式对石墨形态及力学性能的影响。 结果表明，胶囊型缓释孕育工艺显著提升了厚大断面 中心区域的石墨球密度从72个/mm2增至100个/mm2，球化率从70.86%增至81.52%，石墨平均直径从20.51μm降至 18.74 μm。 通过增加的石墨形核核心，达到细化基体晶粒和均匀碳扩散路径的目的，有效抑制了碎块状石墨的生成。 力 学性能测试显示，抗拉强度与伸长率分别提升8.45%(367~398MPa)和29.82%(15.02%~19.5%)。

During the solidification of heavy section ductile iron, the slow cooling rate in the central region tends to reduce the number of graphite nodules, form fragmented graphite, and cause shrinkage defects, significantly weakening its mechanical properties. To solve this problem, a novel capsule-based slow-release inoculation process was proposed. Through capsule-type slow-release inoculation, the release of inoculants is delayed to optimize the graphite morphology and increase the number of graphite nodules. Three groups of samples (HDQT-0, HDQT-0.1, and HDQT-0.3) were prepared via a composite process combining in-ladle impingement spheroidization inoculation with slow release inoculation. The effects of inoculation methods on the morphology and mechanical properties of graphite were comparatively analysed. The results reveal that the capsule-based slow-release inoculation process significantly increases the graphite nodule density in the central region of heavy sections from 72/mm2 to 100/mm2, improves the nodularity rate from 70.86% to 81.52%, and reduces the average graphite diameter from 20.51 μm to 18.74 μm. By increasing the number of graphite nucleation sites, the process refines the matrix grains and homogenizes the carbon diffusion pathways, effectively suppressing the formation of fragmented graphite. Mechanical property tests indicate that the tensile strength and elongation increase by 8.45% (from 367 MPa to 398 MPa) and 29.82% (from 15.02% to 19.5%), respectively.