FE-based development of highly wear resistant hot working tools by alloy modification in combination with a process- and material adapted nitriding layer

在应用研究项目中，将通过实现与工艺和材料相适应的氮化层相结合的适应性合金改性，开发适合热成形工艺特殊要求的适应性热加工工具。在渗氮过程中，通过控制工艺指导，调整确定的渗氮层，研究渗氮深度和硬度梯度对刀具性能的影响。为了调整确定的和可再生的渗氮层，将使用等离子体渗氮工艺。合金改性是在前人研究工作的基础上进行的。在这里，将标准热加工钢与额外量的锰合金化，通过降低奥氏体温度Ac1b来增加循环边缘层硬化的效果。锻件的硬度分布随时间和温度的变化对其耐磨性有显著影响。在原零件成形过程中，模具表面温度急剧升高，最高可达1200℃。表面温度对刀具的热能贡献起决定性作用。由于接触区的高工作负荷，对表面温度的实验测量是不可能的。因此，为了全面考虑边缘层现象，将在项目中使用替代的实验和数值方法。为了表征工具的硬化行为，时间和温度取决于硬度分布，将通过膨胀计试验确定。为了在此测试中使用实际和过程相关的温度曲线，将对工具边缘层的温度曲线进行数值和实验测定。为此，热电偶元件将被放置在模具表面区域附近，具有不同的深度，并且锻造过程的温度分布将被确定。有了这些数据，数值计算的温度曲线将得到验证，表面温度的发展将得到计算。表面温度将用作膨胀计测量的输入值。膨胀计试验结束后，将在行业相关的自动化锻造生产线上进行系列锻造试验。与膨胀试验中的循环时间类似，磨损测量将在锻造试验后进行。这种方法允许研究实验研究的硬度分布与一系列锻造试验中测量的磨损率的可转移性。项目中获得的数据将用于扩展现有的基于fe的磨损模型，该模型考虑了时间和温度对硬度梯度的影响。

Within the applied research project adapted hot working tools for the special requirements in hot forming processes will be developed by realizing an adapted alloy modification in combination with a process- and material adapted nitriding layer. By controlled process guiding during the nitriding process defined nitriding layers will be adjusted to investigate the influence of the nitriding depth and hardness gradient on the tool performance. To adjust defined and reproducible nitrding layers the plasma nitriding process will be used. The alloy modification bases on previous research works. Here, a standard hot working steel will be alloyed with additional amounts of manganese to increase the effect of the cyclic edge layer hardening by lowering the austenitic temperature Ac1b.The time- and temperature depending hardness profile of forging tools has a significant influence on the wear resistance. The surface temperature of the dies increases highly during the forming process of raw parts with a temperature of up to 1200 °C. The surface temperature plays a decisive role on the contribution of thermal energy into the tools. An experimental measurement of the surface temperature is not possible due to the high working loads in the contact zone. Therefore, alternative experimental and numerical methods will be used within the project for a holistically consideration of the edge layer phenomena. To characterize the hardening behavior of the tools time and temperature depending hardness profiles will be identified by dilatometer tests. To use the real and process depending temperature profiles for this test, a numerical and experimental determination of the temperature profile in the edge layer of the tools will be performed. For this purpose, thermocouple elements will be positioned near the surface zones of the dies with varying depth and the temperature profiles as a result of the forging process will be determined. With this data the numerically calculated temperature profiles will be validated and the development of the surface temperature will be calculated. The surface temperature will be used as an input value for the measurements in the dilatometer. After the dilatometer tests, the serial forging tests will be conducted on an industry related automated forging line. Analogous to the cycle times in the dilatometer tests wear measurements will be performed after the forging tests. This approach allows the investigation of the transferability of the experimentally investigated hardness profile with the wear rates measured out of the serial forging tests. The data gained within the project will be used, to expand an existing FE-based wear model considering the time- and temperature depending hardness gradient.