Use of different flow stresses for forming inhomogeneously heated billets

该研究项目的目标是确定坯料的非均匀感应加热对锻造工艺链的后续步骤的影响。因此，应利用不均匀加热坯料中不同的流动应力来影响成形行为。应考虑各种评估标准（飞边、褶皱、成形力），设计和评估钢坯均匀和不均匀加热的不同工艺，以确定潜在风险。此外，还应确定不均匀加热的工艺限值。与工业上已建立的仅对坯料的部分进行加热和成形的部分加热不同，在本研究项目中，整个坯料将被不均匀地加热和成形。研究结果将有助于使批量成型的制造过程在材料使用和能源消耗方面更加有效。针对这一研究目标，可以推导出以下三个子目标：第一个子目标是圆柱形坯料内非均匀温度场感应可调性的模拟和实验研究。为了评估缩放效应，应检查尺寸在常规尺寸范围内差异很大的坯料。可调节性的主要标准是作为时间的函数的温度补偿。第二个子目标的重点是利用有限元模拟研究坯料不均匀加热对锻造工艺链（包括预成形和终锻步骤）的影响。为此，应设计和评估具有不均匀加热坯料的各种工艺链。应设计和评估具有均匀加热坯料的参考工艺，以进行比较。最后，为所有的工艺链确定一个合适的工艺窗口进行实验测试。第三个子目标是不均匀加热坯料对锻造工艺链影响的实验研究。因此，在第二个分目标中通过模拟设计的流程链应在实验测试中复制。随后，考虑到既定的评估标准（例如：飞边、褶皱、成形力），以确定坯料不均匀加热的可能性。为了说明零件的质量，必须对所有零件进行尺寸精度分析和结构分析。

The goal of the research project is to determine the effect of an inhomogeneous induction heating of billets on subsequent steps of a forging process chain. Therefore the different flow stresses in the inhomogeneously heated billet shall be used to influence the forming behavior. Different processes with homogeneous and inhomogeneous heating of billets shall be designed and evaluated considering various assessment criteria (flash, folds, forming force) to determine the potentials. In addition, the process limits of an inhomogeneous heating are to be determined. In differentiation to the industrially established partial heating in which only sections of the billets are heated and formed, the entire billet shall be inhomogeneously heated and formed in this research project. The research results will help to make manufacturing processes in bulk forming more efficient regarding use of materials and energy consumption. For this research goal, the following three sub-goals can be derived.The first sub-goal is the simulation and experimental study of the adjustability of an inhomogeneous temperature field in cylindrical billets by induction. In order to evaluate scaling effects, billets with very different dimensions in the range of customary dimensions shall be examined. The primary criterion of the adjustability is the temperature compensation as a function of time. A FEA-model shall be built and verified by practical heating experiments.The focus of the second sub-goal is the investigation of the effect of inhomogeneous heating of billets to forging process chains with preforming and finish forging steps using FEA-simulations. For this purpose various process chains with inhomogeneous heated billets shall be designed and evaluated. Reference processes with homogeneous heated billets shall be designed and evaluated for comparison purpose. Finally a suitable process window for experimental testing shall be determined for all process chains.The third sub-goal is the experimental study of the effect of inhomogeneously heated billets to a forging process chain. Therefore the processes chains designed by simulations in the second sub-goal shall be replicated in experimental tests. Subsequently, a comparative evaluation of the various process chains considering the established assessment criteria (e.g.: flash, folds, forming forces) has to be done to determine the potential of an inhomogeneous heating of billets. In order to make statements about the parts quality, all parts have to be analyzed with regard to their dimensional accuracy and by a structural analysis.