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利用经典形核理论和扩散控制长大模型计算分析了重轨钢中MnS粒子析出的动力学行为,计算结果表明,MnS粒子在重轨钢凝固过程以均匀形核和晶界形核为主,主要在凝固末期析出。在设定的重轨钢成分下,计算出MnS的有效形核温度为1 634K,即Mn、S实际浓度积等于平衡浓度积。降低S的质量分数小于5.0×10-5能够推迟MnS接近固相线析出,而对MnS的长大半径影响较小;提高冷却速率从0.14K/s到1.45K/s,连铸坯内柱状晶区中MnS的长大半径比中心等轴晶区的大1个数量级,但对MnS的析出时机无影响。S元素是MnS在凝固过程中粗化长大的控制性环节,在凝固过程冷却速率对MnS粒子长大半径起着决定性的作用。
The kinetic behavior of MnS particles precipitation in heavy rail steel was calculated and analyzed by using classical nucleation theory and diffusion controlled growth model. The calculated results show that the MnS particles are mainly formed by uniform nucleation and grain boundary nucleation in the solidification process of heavy rail steel. Mainly in the end of solidification precipitation. Under the set heavy rail steel composition, the effective nucleation temperature of MnS is calculated as 1 634K, that is, the actual concentration product of Mn and S is equal to the equilibrium concentration product. Decreasing the mass fraction of S less than 5.0 × 10-5 can delay the precipitation of MnS near the solidus, but has little effect on the growth radius of MnS. Increasing the cooling rate from 0.14K / s to 1.45K / s, The growth radius of MnS in grain boundaries is one order of magnitude larger than that of equiaxed grains in the center, but has no effect on the precipitation timing of MnS. S element is a controllable aspect of MnS coarsening and growth during solidification. The cooling rate during solidification plays a decisive role in the growth radius of MnS particles.