Nanobainite shows high tempering stability. However, studies of the multi-tempering behavior of nanobainite hot-working die steel are rare. In the present work, the microstructure and mechanical properties of Si–H13 nanobainite steel, subjected to multi-tempering processes, have been investigated via microstructural characterization and mechanical tests. The results show that the filmy retained austenite decomposed into ferrite and granular V₂C during the first tempering process. The size of V₂C increased slightly after the second tempering. VC precipitated from bainitic ferrite of the third tempered sample. Because of hindering effects that decomposition products of filmy retained austenite have on the combination of bainitic ferrite laths, the increment of thickness of bainitic ferrite lath is only 29% (26 nm) after multi-tempering processes. The yield strength of multi-tempered samples is obviously higher (by more than 50%) than that of austempered samples. With an increase in number of tempering, the dominant strengthening contribution changes from grain boundary strengthening and dislocation strengthening to precipitation strengthening. Moreover, the precipitation of carbides results in secondary hardening during the tempering process. Although the thickness of bainitic ferrite lath became coarse, the hardness of the multi-tempered sample was approximately the same as that of austempered sample. Hence, the Si–H13 nanobainite steel exhibits good tempering stability.

纳米贝氏体显示出高回火稳定性。然而，关于纳米贝氏体热作模具钢多次回火行为的研究却很少。在目前的工作中，通过微观结构表征和力学测试研究了经过多次回火工艺的 Si-H13 纳米贝氏体钢的微观结构和力学性能。结果表明，在第一次回火过程中，薄膜状残余奥氏体分解为铁素体和粒状V ₂ C。V ₂的大小第二次回火后C略有增加。VC从第三次回火样品的贝氏体铁素体中析出。由于薄膜状残余奥氏体分解产物对贝氏体铁素体板条组合的阻碍作用，经过多次回火处理后，贝氏体铁素体板条的厚度增量仅为29%（26nm）。多次回火试样的屈服强度明显高于（超过50%）等温回火试样。随着回火次数的增加，主要的强化贡献由晶界强化和位错强化转变为析出强化。此外，碳化物的析出导致回火过程中的二次硬化。虽然贝氏体铁素体板条的厚度变粗，多回火试样的硬度与等温回火试样的硬度大致相同。因此，Si-H13 纳米贝氏体钢具有良好的回火稳定性。