Energy efficient manufacturing chain for advanced bainitic forging steels based on thermo-mechanical processing

如今，汽车工业的锻造行业寻求更多的资源效率更高的工艺。为了在显著降低成本的情况下降低能耗，本项目旨在开发新一代贝氏体钢锻后连续直接冷却的创新工艺链，以取代传统的调质工艺。在该项目的第一阶段，产生了关于三种先进贝氏体钢的形变加工的新知识，从而确定了这些钢的工艺窗口。主要结果表明，通过热机械途径在工业规模上应用这些材料具有很大的潜力，这不仅可以降低能耗，还可以获得力学性能得到改善的贝氏体组织。这些研究还使进一步开发和使用高影响力的科学技术，如使用涡流传感器和高能同步辐射X射线衍射仪进行现场分析，以及实现工业规模的初步锻造，从而将科学和技术方面结合起来。在这一框架中，确定了若干影响和有待澄清的问题。因此，该项目第二阶段的主要目标是改进所获得的知识，并将其转化为机械部件工业生产的可靠战略，从实际趋势来看，是基于传感器控制制造的工业4.0。工作计划侧重于三个主要领域：部件的热机械加工、后处理步骤和机械性能检查。广泛的物理和有限元模拟以及工业规模的锻造实验将使开发适合这些钢的处理策略成为可能。为此，涡流传感器与受控冷却单元相结合的进一步开发和实现将在实际的热机械过程中实现。将对加工后的部件进行有关最终组织和机械性能的表征。将进一步评估与其他表面强化处理的组合，如感应淬火、等离子渗氮和深度轧制/喷丸强化。然后，将从强度和延展性以及疲劳性能方面对所获得的机械性能进行深入分析。特别是，将研究残余奥氏体量和稳定性的影响，因为它被视为改善机械性能的主要载体之一。

The forging sector for the automotive industry nowadays seeks for more resource efficient processes. In order to reduce energy consumption with a possibility of significant cost reduction, this project aims at developing innovative process chains for new generation bainitic steels with continuous direct cooling after forging, replacing the traditional hardening and tempering processes. In the first phase of the project, new knowledge on thermomechanical processing of three advanced bainitic steels was generated, which allowed the definition of process window for these steels. The main results indicate great potential for application of these materials by means of thermomechanical routes on an industrial scale, which, in addition to reducing energy consumption, also make it possible to obtain a bainitic microstructure with improved mechanical properties. The investigations also enabled the further development and use of high impact scientific techniques such as in situ analyses using eddy current sensor and high energy synchrotron XRD as well as the realization of preliminary forging on an industrial scale, thus combining the scientific and technological aspects. In this framework, several effects and open questions were identified, which still need to be clarified. The second stage of the project has therefore as its main objective the improvement and transfer of the acquired knowledge to robust strategies for industrial production of machine components, in the sense of actual trends towards industry 4.0, based on sensor controlled manufacturing. The working plan is focused on three main areas: thermomechanical processing of components, post-processing steps and inspection of mechanical properties. Extensive physical and FEM-simulation as well as industrial scale forging experiments will allow the development of suitable treatment strategies for these steels. For this, further development and implementation of Eddy-current sensors combined with a controlled cooling unit will be realized in real thermomechanical process. The processed components will be characterized concerning the final microstructure and mechanical properties. The combination with additional surface hardening treatments will be further evaluated, as induction hardening, plasma nitriding and deep rolling/ shot peening. The achieved mechanical properties will then be intensively analyzed in terms of strength and ductility but also regarding the fatigue properties. In particular, the influence of the amount and stability of the retained austenite will be investigated, since it is seen as one of the major carrier for improved mechanical properties.