Control of forming behavior by inhomogeneous heating of semi-finished products during cross-wedge rolling

本文研究了利用局部可变流变应力对楔横轧半成品进行非均匀加热的成形行为控制问题。通过不均匀加热半成品，例如在半温暖和温暖地区，材料的流动特性可以适应楔横轧模。这将增加工艺稳定性并防止轧制缺陷。在楔横轧过程中，沿工艺链会出现影响零件质量的不同轧制缺陷。例如，在楔横轧过程中，孔洞、沿半成品纵轴的内部裂纹、内部起皱、表面缺陷、压痕不足、鱼口效应或过滚都可能发生。造成轧制缺陷的一个原因是由于过程稳定性不足，例如，在楔横轧过程中，半成品的滑移或不均匀扭转。在楔横轧过程中，由于局部流动路径的不同而产生滑移或扭转。楔形区域内的物料流动明显大于楔形区域外的物料流动。例如，这会导致不同的扭转。目前，楔形横轧工具中引入了锯齿，例如减少滑移。然而，楔横轧过程中大量的锯齿留下表面缺陷，只能用于没有功能表面的区域。不均匀加热可以减少表面缺陷，通过减少模具中的锯齿数量，另外还可以降低模具成本。此外，不均匀加热也导致半成品的局部结垢减少，提高表面质量。楔横轧半成品不均匀加热的加热策略一直是研究的课题。从进行的初步调查来看，本研究项目的工作假设是半成品的不均匀加热导致更稳定的过程和质量保证的楔横轧过程。本研究项目的目的是确定不均匀的半成品加热对楔横轧过程的影响，以提高轧制质量和工艺稳定性。在特定的非均匀加热半成品中，不同的流动应力被用来特定地影响成形行为，从而提高轧制质量。根据鱼口深度、表面缺陷、内部缺陷概率和扭转来评估轧制质量。工艺稳定性是通过观察半成品的滑移来评估的。

The present research proposal deals with the control of the forming behavior with the aid of locally variable flow stresses through inhomogeneous heating of the semi-finished product during cross wedge rolling. By heating the semi-finished product inhomogeneously, e.g. in half-warm and warm areas, the flow properties of the material can be adapted to the cross wedge rolling die. This should increase process stability and prevent rolling defects. During the cross-wedge rolling process, different rolling defects can occur that influence the component quality along the process chain. For example, voids, internal cracks along the longitudinal axis of the semi-finished product, internal wrinkles, surface defects, insufficient impressions, fishmouth effects or overrolling can occur during cross wedge rolling. One cause of rolling defects is insufficient process stability due to, for example, slippage or uneven torsion of the semi-finished product during the cross-wedge rolling process. Slippage or torsion results from the locally different flow paths during the cross wedge rolling process. The material in the area of the wedge flows significantly more than in the area outside the wedge. This results in different torsions, for example. Currently, serrations are introduced into the cross wedge rolling tool, for example to reduce slippage. However, the large number of serrations leave surface defects during the cross wedge rolling process and can only be used in areas without functional surfaces. Inhomogeneous heating can reduce the surface defects, by reducing the number of serrations in the die and additionally reduce die costs. In addition, inhomogeneous heating also leads to a local reduction in scaling of the semi-finished product and improves surface quality. The heating strategy of inhomogeneous heating of semi-finished products for cross wedge rolling has not yet been the subject of research. From the preliminary investigations carried out, the working hypothesis of this research project is that inhomogeneous heating of semi-finished products leads to a more process-stable and quality-assured cross wedge rolling process. The aim of this research project is to determine the influence of inhomogeneous semi-finished product heating on the cross wedge rolling process in order to increase rolling quality and process stability. Different flow stresses in specifically inhomogeneously heated semi-finished products are to be used to specifically influence the forming behavior and thus increase the rolling quality. The rolling quality is assessed in terms of fishmouth depth, surface defects, internal defect probabilities and torsion. Process stability is assessed by looking at the slippage of the semi-finished product.