Setting an ultrafine grain at forged preforms by using cross wedge rolling

楔横轧生产的预制件被锻造行业用于各种零件。它们的特点是富余材料数量较少。与ECAE相比，楔横轧在工业上得到了实施和确立。与粗晶材料相比，超细晶材料具有更好的力学性能，具有更高的屈服强度和缺口冲击强度。因此，具有超细晶粒的零件可以制造出更轻的零件，从而降低了材料消耗。通过这样节省的材料降低了生产过程中和移动部件的能耗，例如在内燃机使用时也是如此。楔横轧与超细晶零件力学性能的提高相结合，可以大大提高工艺设计和材料效率。因此，本研究项目的目的是开发一种可用于调整锻造预制件的超细增益并可在工业上实施的楔横轧工艺。目标颗粒尺寸与仅在ECAE等研究项目中使用的工艺可生产的颗粒尺寸相同。最终，楔横轧时晶粒的力学性能，如平均晶粒度，应与其几何形状和工艺参数相关联。三个子目标中的第一个目标是开发一种合适的楔横轧工艺，能够成功地成形圆柱体零件。这些工具应该能够系统地变化。在第二个子目标中，必须研究楔横轧过程与成形速度和坯料温度等工艺参数的相关性。在第三个分目标中，应检查楔横轧后冷却条件的相关性。冷却条件根据楔横轧时生长的晶核决定最终的晶粒度。因此，必须研究不同的冷却速度和流体。

Preforms produced by cross wedge rolling are used for a variety of parts by the forging industry. They are characterized by a low amount of surplus material. Compared with ECAE cross wedge rolling is implemented and established in industry. In comparison, an ultrafine grain has better mechanical properties as a higher yield strength and notch impact strength than materials with a coarse grain. Therefore parts with ultrafine grain can be constructed more light-weighted which lowers the material consumption. The material that is saved through this lowers the energy consumption during the production and regarding moving parts, e.g. in combustion engines while usage, too. With the combination of cross wedge rolling and the improved mechanical properties of parts with ultrafine grain the design of processes and material efficiency can be both improved dramatically. The aim of this research project therefore is to develop a cross wedge rolling process that can be used to adjust an ultrafine gain for forging preforms and can be implemented in industry. The target grain size is the same as those producible with processes that are used only in research projects like ECAE. In the end the mechanical properties of the grain like the average grain diameter should be associated with geometry and process parameters at cross wedge rolling. The first of three sub-aims is to develop a suitable cross wedge rolling process that can successfully form cylindrical parts. The tools should be able to be varied systematically. Within the second sub-aim a dependency of the cross wedge rolling process from process parameters like forming velocity and billet temperature has to be investigated. Within the third sub-aim a dependency from cooling conditions after the cross wedge rolling should be examined. The cooling conditions determine the final grain size based on the nuclei grown at cross wedge rolling. Therefore different cooling velocities and fluid have to be investigated.