Three medium-carbon, high-silicon cast steels with different alloy contents were austempered at 330 °C for different holding times in order to obtain carbide-free bainitic microstructures. Aiming at evaluating the influence of holding time and microstructural features on strength and ductility, tensile properties were measured for each steel at selected austempering times. The results obtained indicate that it is possible to adjust holding time in order to obtain the best strength/ductility combination at determined austempering temperature. Moreover, it has been shown that the mechanical stability of retained austenite is the key factor in controlling tensile performance. Short austempering times result in low carbon enrichment of the austenite (low stability) and promote higher ultimate tensile strength and lower ductility. For longer austempering times, steels present a slight decrease in ultimate tensile strength but a marked increase in ductility. This work shows that it is possible to obtain cast steels with ultimate tensile strength of 1682 MPa, yield strength of 1493 MPa and total elongation of 12.5% by means of bainitic reaction. This strength/ductility combination and others reported in this study are remarkable for cast steels.

为了获得不含碳化物的贝氏体组织，对三种具有不同合金含量的中碳高硅铸钢在330°C的温度下进行了不同的保温时间。为了评估保温时间和显微组织特征对强度和延展性的影响，在选定的回火时间下对每种钢的拉伸性能进行了测量。获得的结果表明，可以调节保持时间，以便在确定的回火温度下获得最佳的强度/延展性组合。而且，已经表明，残余奥氏体的机械稳定性是控制拉伸性能的关键因素。短时间的回火时间导致奥氏体的碳富集度低（稳定性低），并提高了极限抗拉强度和延展性。对于较长的回火时间，钢的极限抗拉强度会略有下降，但延展性会明显提高。这项工作表明，可以通过贝氏体反应获得极限抗拉强度为1682 MPa，屈服强度为1493 MPa，总伸长率为12.5％的铸钢。这种强度/延展性的结合以及本研究中报道的其他方面对于铸钢而言非常出色。