热处理过程夹杂物与钢基体界面固相反应机理研究

In this project, the influence of different cooling process on two equilibrium systems at high temperature which are "Fe-Mn-Si alloy & MnO-SiO2-FeO oxide" and “Fe-Al-Ca alloy & Al2O3-CaO-FeO oxide” was studied. In order to open up new technical ideas and process ways for controlling physicochemical characteristics and improve the properties of alloy matrix, solid-state reactions of two kinds of systems namely “Fe-Mn-Si alloy & MnO-SiO2-FeO oxide” and “Fe-Al-Ca alloy & Al2O3-CaO-FeO oxide” during heat treatment and their influence on the compositions and phases in the alloy and oxide were investigated by diffusion couple method. Influence mechanism of sulfur and oxygen on the solid-state reactions and element diffusion was also analyzed and discussed. Based on the experiment results and thermodynamic analysis, heat treatment process system and dynamic theoretical model were developed and constructed to control the modification of MnO-SiO2 and Al2O3-CaO inclusion. Finally, a series of industrial tests was carried out to verify the heat treatment control technology for the two kinds of “alloy & oxide” systems by combining existing industrial technology and processes, thus providing necessary theoretical basis and mature technical scheme for its industrial application and economic and technical assessment.

本项目利用热力学计算和高温凝固平衡实验，研究不同凝固冷却制度对Mn-Si脱氧钢与MnO-SiO2类夹杂物、Al-Ca脱氧钢与Al2O3-CaO类夹杂物两类“钢液-夹杂物”高温平衡体系的影响规律；为控制夹杂物的物化特性和改善钢基体各项性能开辟新的技术思路和工艺途径，研究热处理工艺对以上两类扩散偶样品中钢基体与夹杂物界面固相反应以及二者物化特性的影响规律，探讨和揭示钢基体与夹杂物之间固相反应和扩散机理，并研究硫、氧元素对其的影响规律和机理，进而开发和构建控制MnO-SiO2类夹杂物和Al2O3-CaO类夹杂物变性的热处理工艺体系和动力学理论模型，最终结合已有工业技术和工艺对两类“钢基体-夹杂物”体系的热处理控制技术进行系列工业试验，为该热处理工艺控制体系、理论模型的工业应用和经济技术评价提供必要理论依据和成熟技术方案。

钢中非金属夹杂物的特性对钢材质量有重要影响。经热处理和轧制工序后在钢基体中最终所形成的非金属夹杂物的种类、数量、尺寸、形貌等往往与钢液凝固前的初始夹杂物差异较大。通过合适的热处理工艺实现对合金基体内非金属夹杂物物化特性的控制是可行的。本项目针对“热处理过程夹杂物演变”这一主题，结合热力学平衡计算和高温平衡实验，构建和验证了1873 K温度下MnO-SiO2-FeO非金属氧化夹杂物与Fe-Mn-Si合金以及Al2O3-CaO-FeO系非金属氧化夹杂物与Fe-Al-Ca合金之间平衡关系。利用扩散偶方法研究了1473 K下保温热处理、硫元素、氧元素等分别对上述两类扩散偶样品中合金基体与夹杂物之间界面固相反应以及二者物化特性的影响规律，探讨和揭示了钢基体与夹杂物之间固相反应和扩散机理。研究表明：氧化物中FeO含量的升高能够提高过剩O氧含量，促进合金与氧化物的界面固相反应；硫元素对热处理过程中MnO-SiO2-FeO氧化物和Fe-Mn-Si合金之间元素相互扩散和界面固相反应起抑制作用，但对Fe-Al-Ca合金与Al2O3-CaO-FeO氧化物体系基本无影响。结合实验结果，开发和构建了控制和预测两类固相反应和夹杂物变性的有效动力学理论模型。.取得的主要进展有：.1）开辟了一条控制夹杂物物化特性和改善钢基体洁净度和机械性能的新途径。.2）探索并揭示了热处理过程中Mn-Si脱氧钢与MnO-SiO2类夹杂物、Al-Ca脱氧钢与Al2O3-CaO类夹杂物之间高温固相反应和元素扩散机理。.3）明确了热处理过程中硫、氧元素二者对Mn-Si脱氧钢与MnO-SiO2类夹杂物、Al-Ca脱氧钢与Al2O3-CaO类夹杂物高温界面固相反应以及元素扩散现象的影响规律和作用机理。.4）建立了夹杂物与钢基体之间固相反应的动力学理论模型，为这两类夹杂物的变性处理及预测提供了科学基础。