Use of different flow stresses for forming inhomogeneously heated billets

该研究项目的目标是确定坯料的不均匀感应加热对锻造工艺链后续步骤的影响。因此，需要采用不同的流动应力来影响非均匀加热坯料的成形行为。应考虑各种评估标准(闪蒸、折叠、成形力)来设计和评估不同的钢坯均匀加热和不均匀加热工艺，以确定潜力。此外，还需要确定非均匀加热的工艺极限。与工业上建立的局部加热不同，在本研究项目中，只有部分钢坯被加热和成形，整个钢坯应该被不均匀地加热和成形。研究结果将有助于提高整体成形制造工艺的材料利用率和能耗。针对这一研究目标，提出了以下三个子目标：第一个子目标是圆柱坯内非均匀温度场感应可调性的模拟和实验研究。为了评估结垢效果，应检查在常规尺寸范围内具有非常不同尺寸的坯料。可调性的主要标准是温度补偿作为时间的函数。建立有限元模型，并通过实际加热实验进行验证。第二个子目标的重点是通过有限元模拟研究坯料加热不均匀对预成形和终锻工序锻造工艺链的影响。为此，应设计和评估具有不均匀加热坯料的各种工艺链。为便于比较，应设计和评估具有均匀加热坯料的参考工艺。最后，为所有工艺链确定一个合适的试验工艺窗口。第三个子目标是不均匀加热的坯料对锻造工艺链的影响的试验研究。因此，在第二个子目标中通过模拟设计的过程链应在实验测试中复制。随后，必须考虑已建立的评估标准(例如：闪蒸、折叠、成形力)对各种工艺链进行比较评估，以确定钢坯加热不均匀的可能性。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.