Use of different flow stresses for forming inhomogeneously heated billets

该研究项目的目标是确定坯料不均匀感应加热对锻造工艺链后续步骤的影响。因此，不同的流动应力在不均匀加热坯料应使用影响成形行为。应根据各种评估标准（闪光、褶皱、成形力）设计和评估钢坯均匀加热和不均匀加热的不同工艺，以确定潜力。此外，不均匀加热的工艺极限也要确定。与工业上建立的仅加热和成型部分钢坯的局部加热不同，在本研究项目中，整个钢坯应不均匀加热和成型。研究结果将有助于使制造过程在散装成型更有效地利用材料和能源消耗。对于这个研究目标，可以衍生出以下三个子目标。第一个子目标是通过感应调节非均匀圆柱坯温度场的模拟和实验研究。为了评估结垢效果，应检查在常规尺寸范围内尺寸差异很大的钢坯。可调性的主要标准是作为时间函数的温度补偿。建立有限元模型，并通过实际的加热实验进行验证。第二个子目标的重点是研究坯料不均匀加热对预锻和精锻过程链的影响。为此目的，应设计和评估具有不均匀加热钢坯的各种工艺链。应设计和评估均匀加热钢坯的参考工艺以进行比较。最后，应为所有工艺链确定合适的工艺窗口进行实验检测。第三个子目标是实验研究不均匀加热坯料对锻造工艺链的影响。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得到复制。随后，考虑到已建立的评估标准（例如：闪光、褶皱、成形力），必须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。为了对零件质量作出说明，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.