根据CSiMnCr和CSiMnCrNb实验钢的相变规律，在实验室进行了控轧控冷实验研究，分析了微合金元素Nb对高强度热轧双相钢相变规律、组织和性能的影响。实验结果表明，Nb可显著推迟铁素体和珠光体转变，并显著降低铁素体开始转变温度，但对铁素体终止转变温度和贝氏体转变温度区间基本没有影响。经Nb微合金化后，实验钢的屈服强度和抗拉强度增幅均在100 MPa以上，屈服强度的增幅高于抗拉强度，且在强度大幅度升高的同时，伸长率下降并不明显，表明Nb的细晶强化作用对提高中温卷取热轧双相钢强度级别的效果明显。

In the light of experimental results of transformation in CSiMnCr and CSiMnCrNb tested steels, controlled rolling and controlled cooling experiment of the steels were carried out in lab. The effect of Nb on transformation, microstructure and properties of high strength hot rolled dual phase steels was analyzed. It was shown that Nb markedly retards ferrite and pearlite transformation, and markedly reduces start temperature of ferrite transformation, but has few effects on finish temperature of ferrite transformation and bainite transformation temperature zone. With microalloying of Nb, the yield and tensile strength of tested steels were increased by more than 100 MPa.With nonessential decrease of elongation .So the grain refining strengthening effect of Nb is very effective to enhance the strength of hot rolled DP steel coiled at medium temperature.