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采用热模拟试验机研究了Nb元素对含Ti低碳微合金钢的动态连续冷却转变行为的影响,利用OM和TEM对等温淬火工艺处理后实验钢的显微组织和析出行为进行观察和分析。结果表明:Nb元素使得含Ti低碳微合金钢的动态CCT曲线整体向右下方移动,大大减小了先共析铁素体和珠光体相变区,同时扩大了针状铁素体和贝氏体相变区,在较低冷速时能得到较多的针状铁素体;含Nb-Ti和含Ti两种实验钢经等温淬火工艺处理后的显微组织均由铁素体和马氏体两相组成,铁素体相中析出物平均尺寸分别为6.8、4.2nm,利用Orowan机制对析出强化量进行计算得出析出强化量分别为90.6、142.3 MPa。
The effect of Nb on the dynamic continuous cooling transformation behavior of Ti-bearing low carbon microalloyed steels was investigated by using a thermal simulator. The microstructure and precipitation behavior of the steels treated by isothermal quenching were observed and analyzed by OM and TEM. The results show that the Nb element makes the dynamic CCT curve of Ti-containing low-carbon microalloyed steel move to the lower right, greatly reducing the pro-eutectoid ferrite and pearlite transformation zone, and expanding the acicular ferrite and shellfish Martensitic transformation zone, more acicular ferrite can be obtained at lower cooling rates. The microstructures of both Nb-Ti and Ti-containing steels treated by the austempering process are composed of ferrite and Martensitic two-phase composition, the average size of precipitates in the ferrite phase were 6.8,4.2 nm, using the Orowan mechanism of the amount of precipitation strengthening were calculated precipitation strengthening were 90.6,142.3 MPa.