Increasing the service life of die casting dies is an important goal of the foundry industry. Approaches are either material- or process-related. Despite new material concepts, hot work steels such as H11 are still predominantly used in the uncoated condition for die casting dies. In order to withstand the stresses that occur, this steel is used exclusively in the quenched and tempered condition. Required properties such as high high-temperature strength and high hardness combined with high toughness are, in principle, contradictory and can only be adjusted consistently over the entire die by furnace-based heat treatment. However, the results of various investigations have shown that improvements in the thermal shock resistance and wear resistance of hot work tool steels can be achieved by thermally influencing the microstructure near the surface. Based on these studies and related findings, an approach to surface heat treatment using the electron beam was developed. Due to the particle character of the radiation and the associated possibility of high-frequency beam deflection, the electron beam offers significantly greater flexibility in energy input into the workpiece surface compared with lasers or induction. The overall technological concept envisages replacing furnace-based heat treatment in the production of casting dies by localized and demand-oriented boundary layer heat treatment with the electron beam. The experiments include, on the one hand, the experimental determination of a suitable temperature–time interval with a focus on short-term austenitization. On the other hand, a simulation-based approach of boundary layer heat treatment with validation of a suitable heat source is investigated. Regarding short-term austenitization, the corresponding temperature and time range could be narrowed down more precisely. Some of these parameter combinations seem to be very suitable for practical use. The test specimens show a hard surface layer with a depth of at least up to 6 mm and a very tough buffer layer. Numerical simulation is used to estimate the resulting metallurgical microstructure and the achievable hardness as a function of the temperature–time interval. In addition, the results provided show the possibility of determining and optimizing the material properties by means of a simulation-based approach within the framework of a purely digital process planning and subsequently transferring them into a process planning. In the technical implementation, a temperature control was first established by means of a two-color pyrometer. In the further course of research, the pyrometer will be supplemented by an internally installed infrared camera, which will allow the reproducible setting of specified temperature profiles even for complex, large-area contours in the future.

中文翻译：

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利用电子束技术对压铸模具进行近表面层热处理

提高压铸模具的使用寿命是铸造行业的一个重要目标。方法要么与材料相关，要么与流程相关。尽管采用了新的材料概念，但 H11 等热作钢仍主要用于压铸模具的无涂层状态。为了承受出现的应力，这种钢仅在淬火和回火条件下使用。所需的特性，如高温强度和高硬度与高韧性相结合，原则上是相互矛盾的，只能通过炉基热处理在整个模具上进行一致调整。然而，各种研究的结果表明，热作工具钢的抗热震性和耐磨性可以通过热影响表面附近的微观结构来实现。基于这些研究和相关发现，开发了一种使用电子束进行表面热处理的方法。由于辐射的粒子特性和高频光束偏转的相关可能性，与激光或感应相比，电子束在输入到工件表面的能量方面具有更大的灵活性。整体技术概念设想通过电子束局部和以需求为导向的边界层热处理来代替铸造模具生产中的基于炉的热处理。实验包括，一方面，实验确定合适的温度-时间间隔，重点是短期奥氏体化。另一方面，研究了一种基于模拟的边界层热处理方法，并验证了合适的热源。对于短期奥氏体化，可以更精确地缩小相应的温度和时间范围。其中一些参数组合似乎非常适合实际使用。测试样品显示出深度至少为 6 毫米的坚硬表面层和非常坚韧的缓冲层。数值模拟用于估计所得的金相显微组织和可达到的硬度作为温度-时间间隔的函数。此外，提供的结果显示了在纯数字工艺规划框架内通过基于模拟的方法确定和优化材料特性的可能性，然后将它们转换为工艺规划。在技​​术实施中，首先通过双色高温计建立温度控制。在进一步的研究过程中，高温计将配备一个内部安装的红外摄像头，即使将来对于复杂的大面积轮廓，也可以重复设置指定的温度曲线。