Extrusion Dies with Local Internal Cooling Channels Manufactured by Additive Manufacturing Technologies for Extending the Process Limits in Hot Extrusion

在此资助期内，研究了使用具有保形内部冷却的增材制造挤压模具的基本原理，旨在扩展热铝挤压的工艺窗口。为此，开发了基于层压制造方法和选择性激光熔化的具有靠近模具轴承的冷却通道的模具。除了对模具的结构和设置提出设计建议外，还开发了在模具轴承难以接近的区域检测局部模具温度的测量方法。通过实验和数值模拟研究了坯料、模具和工艺参数之间的相互作用。在限制型材出口温度的同时，通过在热挤压中应用局部模具冷却可以显著提高生产速度。通过将冷却局部化到靠近成形区的区域，与没有模具冷却的参考试验以及较低预热坯料的情况相比，挤压力仅不成比例地增加。即使使用靠近模具轴承的冷却导致局部模具和型材温度的显著降低，也可以检测到影响参数的灵敏度的差异。坯料温度和挤压速度的变化对型材的出口速度的影响大于影响冷却的参数，如冷却通道的尺寸和位置以及冷却剂温度。热挤压生产率的提高可能伴随着模具制造成本的提高。为了克服经济上的缺点，开发了用于热挤压的混合模具部件的第一个概念。为了充分利用这种新型模具技术的潜力，必须开发一种分析模型，用于描述使用模具冷却的热平衡。这将支持冷却的设计和给定参数的工件温度的估计。此外，开发的技术的可移植性，以复杂的模具形状进行了调查。

Within the scope of this funding period the fundamentals for the use of additively manufactured extrusion dies with conformal internal cooling was investigated, aiming at extending the process window of hot aluminum extrusion. For this purpose, dies with cooling channels close to the die bearings on the basis of the layer-laminated manufacturing method and selective laser melting were developed. Besides design suggestions for the construction and set-up of the dies, measuring methods for the detection of the local die temperature in the difficult to access area of the die bearings were developed. The interactions between billet, die, and process parameters were investigated fundamentally by experimental and numerical investigations. While limiting the profile's exit temperature, a significant increase of production speed is possible by applying a local die cooling in hot extrusion. By localizing the cooling to the area close to the forming zone, the extrusion force increase only disproportionately in comparison to the reference trials without die cooling as well as in the case of lower preheated billets. Even though the use of the cooling close to the die bearings leads to significant reductions in the local die and profile temperatures, differences in the sensitivities of the influencing parameters could be detected. A variation of the billet temperature and of the extrusion speed has a higher impact on the profile's exit speed than the parameters influencing the cooling, like the dimension and position of the cooling channel as well as the coolant temperature. The potential of an increased productivity in hot extrusion might be accompanied by higher manufacturing costs for the die. To overcome the economic disadvantages, first concepts for hybrid die components for hot extrusion were developed. For exploiting the full potential of this novel die technology, an analytical model for the description of the heat balance using die cooling has to be developed. This will support the design of the cooling and the estimation of the workpiece temperature with given parameters. Furthermore, the transferability of the developed technology to complex die shapes has to be investigated.