ANOVA test results on the fold depth.

Fold defects represent a prevalent and detrimental issue in the multi-directional die forging of complex valve bodies, often resulting in product rejection and increased manufacturing costs. In this study, a three-dimensional thermo-mechanical coupled finite element (FE) model was developed using Forge® software to simulate the multi-directional die forging process. The “marking grid” and “sensors” functionalities were employed to visualize and track the formation and evolution of fold defects throughout the entire forming process, thereby elucidating the underlying fold formation mechanism. The effects of three key process parameters—initial billet temperature, main punch speed, and friction coefficient between the billet and die—on fold depth and damage value were systematically analyzed. Orthogonal experiments combined with analysis of variance (ANOVA) were conducted to identify the optimal parameter combination. Results indicated that the friction coefficient had the most significant influence on fold formation and damage accumulation, followed by billet temperature, while punch speed had the least impact. The optimal parameters were determined to be a friction coefficient of 0.1, an initial billet temperature of 1200 °C, and a main punch speed of 30 mm/s. Production trials and fluorescent magnetic particle inspection confirmed the absence of fold and crack defects, and the final forged product closely matched the simulation predictions, validating the effectiveness of the optimized process.折叠缺陷是复杂阀体多向模锻过程中普遍存在且危害严重的问题，常导致产品报废并增加制造成本。本研究采用Forge®软件构建了三维热力耦合有限元（FE）模型，以模拟多向模锻工艺。通过启用“标记网格”与“传感器”功能，可视化并追踪了整个成形过程中折叠缺陷的形成与演化过程，从而阐明了折叠缺陷形成的内在机理。系统分析了初始坯料温度、主冲头速度以及坯料与模具间的摩擦系数这三个关键工艺参数对折叠深度与损伤值的影响。结合正交试验与方差分析（ANOVA）确定了最优工艺参数组合。结果表明，摩擦系数对折叠形成与损伤累积的影响最为显著，其次为坯料温度，而冲头速度的影响最小。最终确定的最优参数为：摩擦系数0.1、初始坯料温度1200℃、主冲头速度30mm/s。生产试验与荧光磁粉检测结果证实，锻件无折叠与裂纹缺陷，最终锻件与仿真预测结果高度吻合，验证了优化工艺的有效性。