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采用热模拟实验研究了不同Nb含量的低C高Mn钢在800—900℃变形后奥氏体的回复特征,同时借助Fe-40%Ni-0.1%Nb(质量分数)合金揭示了回复过程中的位错演化及析出行为,建立了位错滑移及溶质拖曳机制的等温回复动力学模型,据此计算拟合了应力松弛曲线上回复实验数据,计算结果与理论分析及实验结果相符.实验及模拟结果表明,Nb溶质拖曳及析出均减慢回复过程,提高变形积累;与Nb溶质拖曳相比,析出能够更有效地延缓回复软化;Nb溶质拖曳通过升高回复激活自由能U0及减小激活长度来实现回复过程的延缓,提高溶质Nb含量,将升高Uo和减小激活长度.对于含Nb低C高Mn微合金钢,在道次间隔短的多道次热连轧精轧阶段,变形积累主要依靠Nb溶质拖曳作用,而对于轧制节奏较慢的中厚板精轧,轧制变形的积累依靠Nb溶质拖曳与析出的共同作用.
The characteristics of austenite recovery after deformation at 800-900 ℃ for low C-Mn steel with different Nb content were investigated by means of thermal simulation. Meanwhile, the recovery of austenite during the recovery process was also revealed by Fe-40% Ni-0.1% Nb (mass fraction) The dislocation evolution and precipitation behavior were established, and the isothermal recovery kinetics model of dislocation slip and solute drag mechanism was established. Based on this, the experimental data of the response on the stress relaxation curve were calculated and the results were in good agreement with the theoretical analysis and experimental results. The simulation results show that Nb solute drag and precipitation all slow down the recovery process and increase the deformation accumulation. Compared with Nb solute drag, the precipitation can delay the softening more effectively. The Nb solute drag activates the free energy U0 and decreases Activation of the length of the recovery process to achieve the delay to improve the Nb content of solute will increase the Uo and reduce the activation length for Nb low C high Mn microalloyed steel in the short track interval of the multi-pass hot strip mill finishing stage , And the deformation accumulation mainly depends on the solute drag of Nb. For the rolling of medium-thick plate with slow rolling speed, the rolling deformation relies on the co-action of Nb solute drag and precipitation.