Passive granular medium-based tube press hardening

该项目的目的是研究被动颗粒介质基管压硬化，以促进无限长度型材部件的制造。型材部件热成形的通用工艺是基于气体介质的。一个问题是气体的可压缩性，因此高成型压力与高风险潜在风险相关，并且由于压力积聚时间的限制，冲程速率受到限制。另一种选择是颗粒介质，它允许钢管的高压耐压和温度稳定性的压力硬化过程。在主动颗粒介质基管压硬化的情况下，成形力是通过向管端插入轴向冲床产生的，并通过颗粒传递给组件。然而，由于内摩擦，颗粒柱不具有流体静力行为。这一特点限制了管材的可生产长度、可实现的膨胀和小半径的成形性。为了消除这些显著的限制，实现易于应用，必须研究被动颗粒介质基管压硬化。在此工艺原理中，成形力是通过闭合成形模产生的。通过侧向压力的积累，不仅消除了管材长度的限制，而且可以通过压缩管材截面来延长可达到的应变路径和型材形状。为了实现项目目标，将考虑几何条件，运动学，颗粒填充和温度控制等参数的影响。在此基础上，分析了压力和温度分布对应变和力学性能的影响。因此，必须确定工艺限制和工作区域。该项目首先对陶瓷珠和石英砂作为成型介质，22MnB5作为管道材料及其相互作用进行了表征。有了这些知识，项目进一步包含了工艺设计和最终产品的特性。除了数值模拟外，还需要一个解析模型来确定颗粒介质和管道组件中的压力和温度分布。理论研究还包括微观组织的演变，以便根据不同的工艺条件获得不同强度的构件。为了验证这一点，在实验中研究了不同的变形，如在轴向无颗粒流动的二维成形或在诱导轴向流动的情况下成形，以产生具有梯度横截面面积的型材。此外，将开发新的工具技术，通过分流加热的方式为管道部件供热，使颗粒填充和插入工具后直接进行原位加热过程，以获得最大的有效冷却速率。

The aim of the project is the investigation of the passive granular medium-based tube press hardening to facilitate the manufacturing of profile components with an unlimited length. The common process for hot forming of profile components is based on gaseous media. A problem is the compressibility of the gas, so that high forming pressures are associated with a high-risk potential and limit in the stroke rate due to the pressure build-up time.An alternative are granular media, which allow the press hardening process of steel pipes by high pressure resistance and temperature stability. In the case of active granular medium-based tube press hardening, the forming force is generated by an axial punch insertion into the pipe end and transferred to the component via the granules. However, due to the internal friction, the granule column does not behave hydrostatically. This feature leads to the limitation of the producible pipe length, the achievable expansion and formability of small radii. In order to remove these significant restrictions and to achieve the ease of application, the passive granular medium-based tube press hardening has to be researched. In this process principle, the forming force is generated by closing the forming die. By the lateral pressure build-up not only the limitation of the tube length is removed, but also the attainable strain paths and profile shapes are extended by the compression of the tube cross-section.To achieve the project objective, the influence of the parameters such as e.g. the geometric conditions, the kinematics, the granular filling and the temperature control will be taken into account. Based on this, the pressure and temperature distribution will be analyzed, which influence the strains and mechanical properties. Accordingly, process limits and a working area have to be determined.The project starts with the characterization of the ceramic beads and the quartz sand as forming media, the 22MnB5 as a pipe material and their interactions. With this knowledge, the project contains furthermore the process design and the resulting product properties. In addition to the numerical simulation, an analytical model is necessary to determine the pressure and temperature distribution in the granular medium and the pipe component. The theoretical investigation also includes the evolution of the microstructure, so that depending on the process conditions components of different strength can be obtained. For validation, different variants are studied in an experiment, such as the two-dimensional forming without granular flow in the axial direction or the forming with induced axial flow for producing profiles with graded cross-sectional area. In addition, the new tool technology will be developed in terms of the heat supply of the pipe component by shunt heating, so that the in-situ heating process takes place directly after the granular filling and insertion into the tool for a maximum effective cooling rate.