It is an important challenge to reduce the carbon content in nanostructured bainitic steels for commercialization purposes while still being able to gain the desired microstructural characteristics in nanoscale and not to deteriorate the strength–ductility combinations. That is the point at which an appropriate heat treatment procedure design would be an important parameter. This article aims to investigate how to obtain nanostructured bainite in steel with 0.26 wt% carbon content by applying multi-step austempering procedures. One-, two- and three-step austempering processes have been implemented, and proper heat treatment temperatures and approaches were selected based on dilatometry tests. Results indicated that it has become possible to achieve bainitic ferrites and austenite films with overall thicknesses of 164, 145 and 132 nm and 134, 105 and 90 nm at the end of one-, two- and three-step austempering heat treatments, respectively. Meanwhile, microstructural characteristics resulted in enhanced mechanical properties with ultimate tensile strength (UTS) of 1435, 1455 and 1428 MPa in combination with elongation levels of 15.4, 13.6 and 11.4% after implementing those heat treatments. Finally, it has been shown that applying the multi-step austempering heat treatments resulted in enhanced yield strength and impact toughness values due to the microstructural characteristics and proper heat treatment procedure design.

减少纳米贝氏体钢中的碳含量以实现商业化是一个重要的挑战，同时仍要获得纳米级所需的显微组织特征并且不破坏强度-延展性组合。在这一点上，适当的热处理程序设计将是重要的参数。本文旨在研究如何通过采用多步奥氏体回火程序在碳含量为0.26 wt％的钢中获得纳米结构贝氏体。已经实施了一步，两步和三步的回火工艺，并根据膨胀试验选择了合适的热处理温度和方法。结果表明，可以实现总厚度为164、145和132 nm以及134的贝氏体铁素体和奥氏体薄膜，一步，两步和三步回火热处理结束时分别为105 nm和90 nm。同时，微观结构特性提高了机械性能，在实施这些热处理后，其极限抗拉强度（UTS）为1435、1455和1428 MPa，伸长率分别为15.4、13.6和11.4％。最后，已经表明，由于显微组织特性和适当的热处理程序设计，应用多步奥氏体回火热处理可提高屈服强度和冲击韧性值。实施这些热处理后，压力分别为1455和1428 MPa，伸长率分别为15.4、13.6和11.4％。最后，已经表明，由于显微组织特性和适当的热处理程序设计，应用多步奥氏体回火热处理可提高屈服强度和冲击韧性值。实施这些热处理后，压力分别为1455和1428 MPa，伸长率分别为15.4、13.6和11.4％。最后，已经表明，由于显微组织特性和适当的热处理程序设计，应用多步奥氏体回火热处理可提高屈服强度和冲击韧性值。