【摘要】 在DIL 805A膨胀仪上测定了Nb微合金化1000 MPa级冷轧双相钢连续加热及两相区保温过程中的热膨胀曲线,根据杠杆定律计算的奥氏体体积分数与定量金相测量值符合较好。740、770和800℃保温100 s的过程中,奥氏体的等温相变动力学曲线明显分为两个阶段,两个阶段可分别由JMAK方程描述。第Ⅰ阶段时间指数较大,奥氏体体积分数增长较快,奥氏体长大由C的扩散控制;第Ⅱ阶段时间指数降低,奥氏体体积分数的增长明显变慢,奥氏体长大转变为由Mn的扩散控制。在较低的保温温度下,奥氏体长大可以更快的由C扩散控制转变为由Mn扩散控制。更多还原

【Abstract】 Thermal expansion curves of a Nb microalloyed cold rolled dual phase steel with ultra high tensile strength(>1000 MPa) during continuous heating and soaking in two-phase region were detected on a DIL 805A dilatometer.The austenite isothermal transformation kinetics was calculated using lever rule method,and the results were in good agreement with that by the quantitative metallography method.At the soaking temperatures of 740,770 and 800 ℃ for 100 s,the curves of isothermal transformation kinetics can be separated into two stages.Both the two stages can be predicted by JMAK equations.The austenitic volume fraction increased rapidly in the first stage and the growth of austenite was controlled by carbon diffusion.In the second stage,the rate of austenite growth controlled by manganese diffusion slowed down obviously.The controlling factor of austenite growth changed more easily from carbon to manganese diffusion at the lower soaking temperature.更多还原