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SKD11冷作模具热处理后经磨削加工入库放置时检查一侧表面发现裂纹。通过直读光谱仪、硬度计、金相显微镜、电子探针分别对模具化学成分、硬度、夹杂物以及金相组织进行检测分析。结果表明:原始显微组织不均匀、条带状成分偏析严重,晶粒粗大、晶界宽化的过热倾向以及残留奥氏体多回火不足等因素,造成马氏体转变时淬火残余应力过大,在淬火过程中及后续的模具放置应力释放过程中,内应力最终超过材料的强度极限,导致SKD11冷作模具表面裂纹的加速形成及纵深扩展。
SKD11 cold die after heat treatment by grinding into the storage place to check the surface of the cracks found. Through direct reading spectrometer, hardness tester, optical microscope and electronic probe, the chemical compositions, hardness, inclusions and microstructure of mold were tested and analyzed respectively. The results show that: the original microstructure is not uniform, the segregation of banded components is serious, coarse grains, overheating tendency of grain boundary broadening and insufficient residual tempering of austenite and other factors, resulting in martensitic transformation quenching residual stress too Large, during quenching and subsequent release of the mold release stress, the internal stress eventually exceeds the material strength limit, resulting in SKD11 cold mold surface crack formation and accelerated the depth of expansion.