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

如今，汽车行业的锻造部门寻求更有效的资源利用流程。为了减少能源消耗和显著降低成本的可能性，该项目旨在开发新一代贝氏体钢的创新工艺链，在锻造后连续直接冷却，取代传统的淬火和回火工艺。在项目的第一阶段，产生了关于三种先进贝氏体钢的热机械加工的新知识，从而可以定义这些钢的工艺窗口。主要结果表明，这些材料在工业规模上的应用具有很大的潜力，除了降低能耗外，还可以获得具有改善力学性能的贝氏体微观结构。这些研究还促进了高影响科学技术的进一步发展和使用，例如使用涡流传感器和高能同步加速器XRD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。在这个框架内，确定了若干影响和悬而未决的问题，这些问题仍需澄清。因此，该项目的第二阶段的主要目标是根据工业4.0的实际趋势，在传感器控制制造的基础上，将所获得的知识改进和转移到机器部件的工业生产的稳健策略中。工作计划集中在三个主要领域：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允许开发适合这些钢的处理策略。为此，进一步开发和实现涡流传感器与控制冷却装置相结合，将在实际的热机械过程中实现。加工后的部件将根据最终的微观结构和力学性能进行表征。将进一步评估与其他表面硬化处理的组合，如感应淬火、等离子渗氮和深滚/喷丸强化。获得的机械性能将在强度和延展性方面进行深入分析，同时也要考虑疲劳性能。特别是，将研究残余奥氏体的数量和稳定性的影响，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.