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为更精确地控制及优化X70管线钢的目标组织,以经典相变理论模型为基础,建立了先共析铁素体周围的临界碳浓度与原奥氏体的碳浓度之间的数学模型,并采用逆向回归法确定了铁素体相变分数的关键性参数,经试验验证,模型具有良好的精度。结果表明:临界碳浓度满足c*=1.8c0关系;铁素体相变分数的关键性参数m=1.3,b1=0.026,b2=-3.2;以冷速5℃/s为临界点,冷速对铁素体相变开始点的影响程度有明显变化;锰和铌含量对于铁素体相变开始温度的影响主要体现在α/γ界面处的溶质拖曳作用,铁素体相变开始温度由冷却速率和原始奥氏体晶界面积的乘积决定。
In order to control and optimize the target organization of X70 pipeline steel accurately, the mathematical model between the critical carbon concentration around pro-eutectoid ferrite and the carbon concentration of the original austenite was established based on the classical theory of phase transformation. The key parameters of the ferrite transformation temperature were determined by inverse regression method. The experimental results show that the model has good accuracy. The results show that the critical carbon concentration satisfies the relationship of c * = 1.8c0. The critical parameters of the ferrite transformation fraction are m = 1.3, b1 = 0.026, b2 = -3.2. When the cooling rate is 5 ℃ / s, The effect of manganese and niobium content on the onset temperature of ferrite transformation is mainly reflected by the solute drag at the α / γ interface. The onset temperature of ferrite transformation is controlled by The product of the cooling rate and the original austenite grain boundary area is determined.