目的 针对A356铝合金转向节倾转重力铸造生产中废品率偏高的问题,探索有效的工艺改进方案,以降低铸件关键部位的孔隙率并提升产品成品率。方法 构建“缺陷表征-机理反演-工艺调控”的闭环研究框架。首先,利用X射线无损检测与扫描电镜（SEM）对铸件缺陷进行识别与分类,并统计各部位的废品率分布。其次,基于MAGMAsoft平台对充型流场、温度场及凝固行为进行多物理场耦合仿真,分析缺陷形成机制。最后,根据仿真结果提出多因素协同优化策略：在中心孔热节处增设补缩冒口,在厚大部位引入基于凝固时序控制的强制风冷系统,并将模具预热温度由450 ℃下调至400 ℃以构建合理的界面温度梯度。结果 缺陷检测识别出中心孔缩孔、减震器孔缩松及浇口卷气3类典型缺陷,其中中心孔处废品率高达37.3%。仿真分析表明,局部模数比过大引发的“孤立热节”效应及充型初期流速突变导致的湍流卷气是主要缺陷成因。工艺优化后,铸件关键部位的孔隙率由0.18%显著降至0.01%,优于VDG P201标准的一级要求。结论 所提出的补缩冒口设置、强制风冷及模具预热温度调控等协同优化措施能够有效消除热节与卷气风险,显著提升转向节的成形质量与成品率,可为同类铝合金铸件的工艺改进提供参考。
Abstract
To address the high rejection rate in tilt gravity die casting of A356 aluminum alloy steering knuckles, the work aims to explore effective process improvement solutions to reduce porosity at critical sections of castings and raise the product yield. A closed-loop framework of “defect characterization, mechanism analysis, and process optimization” was constructed. Firstly, X-ray inspection and scanning electron microscopy (SEM) were employed to identify and classify casting defects and the rejection rate distribution at various positions was statistically analyzed. Secondly, multi-physics-field coupled simulation of filling flow field, temperature field and solidification behavior was carried out on the MAGMAsoft platform to analyze the defect formation mechanism. Finally, a multi-factor collaborative optimization strategy was proposed based on the simulation results: adding feeding risers at the hot spot of the central hole, introducing a forced air-cooling system based on solidification sequence control for heavy-section regions, and lowering the mold preheating temperature from 450 ℃ to 400 ℃ to establish a reasonable interfacial temperature gradient. Three typical defects were identified: shrinkage cavity at the center hole, shrinkage porosity at the shock absorber hole, and gas entrapment at the gate, with the center hole exhibiting a rejection rate of 37.3%. Simulation results showed that the “isolated hot spot” effect induced by an excessive local modulus ratio and turbulent gas entrapment caused by abrupt flow velocity variation at the initial filling stage constituted the main defect-forming mechanisms. After process optimization, the porosity at critical sections of the casting decreased significantly from 0.18% to 0.01%, satisfying Grade-I requirements specified in VDG P201 standard. The proposed collaborative optimization measures, including feeding riser arrangement, forced air cooling and mold preheating temperature regulation, can effectively eliminate risks of hot spots and gas entrapment, and substantially improve the forming quality and yield of steering knuckles. This work can provide references for process improvement of similar aluminum-alloy castings.
关键词
重力铸造 /
铝合金转向节 /
MAGMA仿真 /
热节 /
工艺优化 /
孔隙率
Key words
gravity casting /
aluminum alloy steering knuckle /
MAGMA simulation /
hot spot /
process optimization /
porosity
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基金
2025年吉林省教育厅科学研究项目（JJKH20251882KJ）; 2024年度长春职业技术大学智能车载光电信息科学与技术创新团队及应用技术研发与服务项目（2024YFP08）
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