Ca2SiO4-Ca3(PO4)2固溶体生成动力学及溶解行为研究

Slag is the only phase for dephosphorization during iron and steel smelting process. The trajectory of dephosphorization involves the distribution of phosphorus between steel and slag and the distribution of slag phase. Phosphorus dissolved in Ca2SiO4 phase as Ca2SiO4-Ca3(PO4)2 mainly of which the formation and stability is very critical for dephosphorization. The significance of this project is to improve the dephosphorization technology with less slag smelting such as slag-remaning and double slag or new double slag technology. The traditional theory of dephosphorization research focused on the distribution of phosphorus between steel and slag. There is few research about the mechanism on the phosphorus distribution in slag phase, especially the related kinetics research. At first, thermal experiment can be adopted to study the diffusion coefficient, mass transfer coefficient of phosphorus during the formation process of Ca2SiO4-Ca3(PO4)2 solid solution, and dynamic model can be established. Then the dissolved quantity change of Ca2SiO4-Ca3(PO4)2 solid solution with time in the dissolution process can be obtained by establishing dissolving rate equation of Ca2SiO4-Ca3(PO4)2 solid solution. Finally, the mechanism on the dissolution of Ca2SiO4-Ca3(PO4)2 solid solution can be revealed. The completion of this project will refine the dephosphorization theory of converter smelting with less slag, which has a high academic significance and practical application value.

钢渣作为钢中磷脱除的唯一场所，磷的脱除轨迹涉及钢与渣之间分配及渣相间分配。由于钢渣中磷主要以Ca2SiO4-Ca3(PO4)2的形式固溶在2CaO·SiO2 相中，其形成与稳定对于磷的脱除极为关键。为了完善转炉留渣双渣法或新双渣法等少渣冶炼脱磷技术，针对传统脱磷理论研究多集中于磷在钢与渣之间的分配，而磷在渣相间分配机理，特别是相关动力学研究缺乏等现状，本项目拟首先通过热态实验研究转炉脱磷过程中Ca2SiO4-Ca3(PO4)2固溶体形成时磷的扩散系数、传质系数，并建立动力学模型；之后研究Ca2SiO4-Ca3(PO4)2 固溶体溶解过程中溶解量随时间的变化规律，建立Ca2SiO4-Ca3(PO4)2固溶体溶解的速率方程，探明Ca2SiO4-Ca3(PO4)2固溶体的溶解机理。项目的开展可完善转炉少渣冶炼脱磷相关理论，具有较高的学术意义和实际应用价值。

钢渣作为钢中磷脱除的唯一场所，磷的脱除轨迹涉及钢与渣之间分配及渣相间分配。由于钢渣中磷主要以C2S-C3P（Ca2SiO4-Ca3(PO4)2）的形式固溶在2CaO·SiO2相中，其形成与稳定对于磷的脱除极为关键。为了完善转炉留渣双渣法或新双渣法等少渣冶炼脱磷技术，针对传统脱磷理论研究多集中于磷在钢与渣之间的分配，而磷在渣相间分配机理，特别是相关动力学研究缺乏等现状，本项目通过理论计算及热态实验研究C2S-C3P含磷固溶体形成及溶解的动力学条件，研究结果表明： .（1）炉渣碱度1.0处于CaSiO3初生区，而炉渣碱度1.5~2.5则处于2CaO·SiO2初生区。炉渣碱度1.0时CaSiO3的大量生成不利于钢液脱磷，而碱度2.5时，虽然有大量2CaO·SiO2生成，但富磷相中磷含量低，不能充分发挥炉渣的脱磷能力，从炉渣物相的角度分析，适宜含磷固溶体生成的碱度为1.5~2.0，该碱度范围可作为转炉冶炼前期脱磷阶段炉渣碱度参考控制范围。.（2）1450℃不同时间氧化钙、硅酸一钙、硅酸二钙浸入实验渣中，随着反应时间的延长磷元素的扩散深度增加。相同时间硅酸二钙中磷元素的扩散深度与硅酸一钙相近，两者比氧化钙中磷元素的扩散深度更深，磷元素更易在硅酸二钙和硅酸一钙中扩散。C2S-C3P含磷固溶体生成的限制性环节为渣中的磷传质到渣-CaO界面及磷在C2S-C3P含磷固溶体中的传质。磷在C2S-C3P含磷固溶体产物层的有效传质系数DA=1.07×10-11m2/s，磷在渣中的传质系数k=1.33×10-6m/s。.（3）实验条件下C2S-C3P含磷固溶体的溶解量（M）与保温时间（t）、保温温度（T）、电机旋转速度（υ）之间的关系式分别为：M=0.083t+0.164，M=0.0131T-18.3069，M=0.0061υ+1.691。通过控制合适的冶炼时间、适度降低冶炼温度、转炉冶炼后期降低吹氩流量等方法，能减少或抑制C2S-C3P含磷固溶体的溶解，从而实现高效脱磷。