Hong Myoung-Pyo, Kim Young-Suk
Mechanical components and Materials R&D Group, Korea Institute of Industrial Technology, Daegu 711-883, Korea.
Graduate School, Kyungpook National University, Daegu 41566, Korea.
Materials (Basel). 2020 Dec 3;13(23):5516. doi: 10.3390/ma13235516.
Metal additive manufacturing (AM) is a low-cost, high-efficiency functional mold manufacturing technology. However, when the functional section of the mold or part is not a partial area, and large-area additive processing of high-hardness metal is required, cracks occur frequently in AM and substrate materials owing to thermal stress and the accumulation of residual stresses. Hence, research on residual stress reduction technologies is required. In this study, we investigated the effect of reducing residual stress due to thermal deviation reduction using a real-time heating device as well as changes in laser power in the AM process for both high-hardness cold and hot work mold steel. The residual stress was measured using an X-ray stress diffraction device before and after AM. Compared to the AM processing conditions at room temperature (25 °C), residual stress decreased by 57% when the thermal deviation was reduced. The microstructures and mechanical properties of AM specimens manufactured under room-temperature and real-time preheating and heating conditions were analyzed using an optical microscope. Qualitative evaluation of the effect of reducing residual stress, which was quantitatively verified in a small specimen, confirmed that the residual stress decreased for a large-area curved specimen in which concentrated stress was generated during AM processing.
金属增材制造（AM）是一种低成本、高效率的功能模具制造技术。然而，当模具或零件的功能部分不是局部区域，且需要对高硬度金属进行大面积增材加工时，由于热应力和残余应力的积累，增材制造过程中AM材料和基体材料经常出现裂纹。因此，需要开展残余应力降低技术的研究。在本研究中，我们研究了使用实时加热装置减少热偏差所引起的残余应力的效果，以及在高硬度冷作和热作模具钢的增材制造过程中激光功率的变化。在增材制造前后，使用X射线应力衍射装置测量残余应力。与室温（25°C）下的增材制造工艺条件相比，当热偏差降低时，残余应力降低了57%。使用光学显微镜分析了在室温以及实时预热和加热条件下制造的增材制造试样的微观结构和力学性能。在小试样中得到定量验证的残余应力降低效果的定性评估证实，对于在增材制造过程中产生集中应力的大面积弯曲试样，残余应力有所降低。
