CAREER: The Production of High Value, Defect-free Metal Castings through Model-based Design and Additive Manufacturing of Sand Molds

该学院早期职业发展（CAREER）资助的重点是使用基于模型的设计和三维打印砂型的金属铸造研究。 金属铸造包括将熔融金属倒入由砂制成的模具中。它是许多工业应用中生产零件和组件的最古老和最广泛使用的制造工艺之一。然而，传统的金属铸造具有高废品率，因为它仍然被认为是经验设计的过程，并且即使在受控的加工环境中也具有高不确定性。由于用于熔融金属的通道的二维几何形状的性质，湍流将空气捕获在熔体中并在凝固的铸件中引起缺陷。这导致差的机械性能沿着增加修理或报废铸件的成本和能量。该项目进行基础研究，使新的数值模型和计算能力，以研究砂型的三维几何形状和减少砂型铸件缺陷之间的复杂关系。这项研究是由一个综合的教育和推广计划的基础上，新的课程开发，通过铸造教育工作者的网络在美国战略部署的补充。此外，在家庭机构的制造业教育中心是利用代表性不足的少数民族和K-12学生外展。本研究的目的是了解砂型铸造中的三维自由形式浇注和冒口几何形状对减少缺陷和提高金属铸件机械性能的影响。金属熔体的湍流充型导致铸件中氧化物双膜、气泡和气孔的形成，从而对铸件的机械性能产生不利影响。本计画之研究目标为：（1）了解三维自由型浇注系统与冒口设计对充型过程中空气夹带与氧化物双膜形成之影响;（2）探讨三维自由型浇注系统与冒口系统与凝固行为之关系及其对机械强度之影响。该项目利用增材制造工艺，即铸造砂的粘合剂喷射或3D砂打印，用于制造金属铸造的砂模。这项研究建立了一个基本的理解三维浇口和冒口设计几何形状的砂型无缺陷的金属铸件。熔体流动速度，流体动力学，凝固速率，和微观性能，如枝晶臂间距，夹杂物和孔隙率进行了研究。开发并验证了可以通过模具的3D砂印实现的3D浇口和冒口几何形状的设计原则。该项目使PI能够推进金属铸造科学、计算流体动力学建模和铸造过程的过程监控的知识，并为在先进制造领域的长期职业生涯奠定基础。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) grant focuses on the study of metal casting using model-based design and three-dimensional printed sand molds. Metal casting involves pouring of molten metal in a mold made of sand. It is one of the oldest and most widely used manufacturing processes in the production of parts and components for many industrial applications. However, traditional metal casting suffers from high scrap rates because it is still regarded as a process that is empirically designed and with high uncertainty even in controlled processing environments. Due to the nature of the two-dimensional geometry of pathways for the molten metal, turbulent flow traps air in the melt and causes defects in the solidified castings. This results in poor mechanical properties along with additional costs and energy to repair or scrap the castings. This project conducts fundamental research to enable new numerical models and computational capabilities to study the complex relationships between the three-dimensional geometry of the sand mold and reduction in defects in the sand castings. This research is complemented by an integrated educational and outreach program based on new course development to be strategically deployed across the U.S through a network of foundry educators. In addition, a manufacturing education center at the home institution is leveraged for underrepresented minority and K-12 student outreach. The goal of this research is to understand the effects of 3D freeform gating and riser geometry in sand casting on reducing defects and improving the mechanical properties of metal castings. Turbulent filling of molten metal results in the formation of oxide bifilms, air entrapment and porosity in castings, which adversely impact their mechanical performance. The research objectives of the project are: (1) Understand the effects of 3D free-form gating and riser design on air entrapment and formation of oxide bifilms during mold filling, and (2) Characterize the relationship between 3D freeform gating and riser system and solidification behavior and their impact on mechanical strength. This project leverages an additive manufacturing process, namely binder-jetting of foundry sand or 3D sand-printing for the fabrication of sand molds for metal casting. This research establishes a fundamental understanding of 3D gating and riser design geometries in sand molds for defect-free metal castings. Melt flow velocity, fluid dynamics, solidification rate, and microscopic properties such as dendrite arm spacing, inclusions and porosity are investigated. Design principles for 3D gating and riser geometries that can be achieved by 3D sand-printing of molds are developed and validated. This project enables the PI to advance the knowledge of metal casting science, computational fluid dynamics modeling and in-process monitoring of the casting process and establishes the foundation for a long-term career in advanced manufacturing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.