Tailored Carburization: Adjusted mechanical Properties in blank plane and blank thickness direction

该项目的目标是开发和表征通过金属板的局部渗碳调整局部机械性能的基本可能性。因此，必须发展一种基于表面硬化方法的工艺控制策略。因此，在整体金属成形中，表面硬化用于材料的表面硬化，从而导致例如齿轮的齿根和齿侧的疲劳强度增加。因此，在块体金属成形中，表面硬化是一种成熟的工艺，而在传统的金属板成形中，表面硬化是一种新颖的创新方法。因此，对于由平板金属制成的具有不同碳含量的部件的生产的基本知识完全缺失。然而，这些不同碳含量的影响和形成的知识代表了一个关键因素，即考虑到组件和工艺复杂性的持续增加，这是由于对单个部件的功能集成的需求不断增加，部分相互冲突。因此，有必要开发关于材料中碳扩散的工艺特定约束的基本关系，并分析与扩散行为相关的不同工艺参数的影响，以确定合适的工艺窗口。由于扩散是一个随时间变化的过程，额外的调查是必要的，以分析时间依赖的限制，导致整体渗碳的金属板。如果使用较短的渗碳时间，则所得的机械性能将在坯料的厚度方向上改变，从而导致不同的裂纹行为，这是示例性地研究的。此外，在炉中的停留时间的影响，关于局部渗碳和不渗碳部分之间的过渡区的发展进行了研究，这是至关重要的产品性能，由于在这方面的机械性能的变化。此外，不同的图案可以通过导致另一种扩散行为的碳的局部浓度来影响所得的机械性能。由于硬化过程应在刀具中进行，因此必须通过详细的热分析和机械过程来表征附加工艺参数，如施加的接触压力和接触条件。预计石墨支持冷却过程，因为其热导率高于钢的热导率，并且表面粗糙度被石墨填充，另外，即使施加较低的接触压力，也会导致接触表面扩大。最后，确定的影响的新的，创新的方法，关于局部渗碳的金属板进行验证转移到一个模型的几何形状。

The project objective is the development and characterization of the fundamental possibilities regarding the adjustment of local mechanical properties by a localized carburization of sheet metal. Therefore, a process control strategy based on the methodology of case hardening used in bulk metal forming has to be developed. Hereby, in bulk metal forming case hardening is used for surface hardening of the material resulting in increased fatigue strength in tooth root and flank of for example a gear. Thereby, in bulk metal forming case hardening is a well-established process while in conventional sheet metal forming it is a novel, innovative approach. Consequently, fundamental knowledge for the production of components with different carbon content made out of flat sheet metal is missing, totally. The knowledge of the influence and the formation of these different carbon contents, however, represent a critical factor considering the continuing increase in the complexity of the components and processes by rising, partly conflicting requirements and additional demands for functional integration in individual parts. Therefore, it is necessary to develop the fundamental relations regarding process-specific constraints of diffusion of carbon in the material and to analyze the influence of different process parameters related to the diffusion behavior in order to identify a suitable process window. Since diffusion is a time-variant process additional investigations are necessary to analyze the time depending constraints resulting in an integral carburization of the sheet metal. If shorter carburization times are used the resulting mechanical properties will change in thickness direction of the blank leading to a different crack behavior which is investigated exemplarily. In addition, the impact of the residence time in the oven regarding the development of transition zones between locally carburized and not carburized sections is investigated which is crucial for the product performance due to the changing mechanical properties in this area. Furthermore, different patterns can influence the resulting mechanical properties by local concentration of carbon resulting in another diffusion behavior. Due to the fact that, the hardening process should occur in the tool, additional process parameters like applied contact pressure and contact conditions have to be characterized by detailed thermo-analytical and mechanical procedures. It is expected that the graphite is supporting the cooling process due to the thermal conductivity is higher than that of steel and surface asperities are filled by graphite, additionally, resulting in an enlarged contact surface even with lower applied contact pressures. Finally, the identified impacts of the novel, innovative approach regarding the localized carburization of sheet metal are verified by transfer to a model geometry.