凝固过程重轨钢中MnS粒子形核与长大动力学分析

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。

Nucleation and growth dynamics analysis of MnS particles during solidification process in heavy rail steels

Kinetic behavior of MnS particles nucleation precipitation in heavy rail steel was calculated and analyzed by using the classical nucleation theory and a diffusion-controlled growth model.The results show that the MnS particles in heavy rail steel are mainly homogeneous nucleation and grain boundary nucleation during solidification,and mainly precipitate at the end of solidification.The effective precipitation temperature of MnS nucleation in the heavy rail steel is 1 634 K which the actual concentration of Mn and S is equal to their equilibrium concentration.Precipitation of MnS particles is postponed by decreasing the content of sulfur less than 5.0 × 10-5,while it has less effect on the size of MnS particle.The size of MnS particles in the columnar zone of bloom is one order of magnitude larger than those in the center of equiaxed zone by increasing the cooling rate from 0.14 K/s to 1.45 K/ s,but it has less effect on the time of MnS precipitation.The controlled element of MnS growth and coarsening in steels is sulfur during solidification,the growth of MnS particles is affected by the cooling rate during solidification.