转炉钢渣的相演变和自粉化规律研究

Converter slag is a by-product in the processing from iron to steel, about 100 million tons were produced in 2012 China alone. Reusing these slags as recycled material can be regarded as a way to reduce environmental pollution and consumption of natural materials. However, the poor grindability caused by complex chemical composition and microstructure of converter slag makes it very difficult to be recycled. Converter slag contains 30-60% polymorph dicalcium silicate (C2S), whose crystal structure can be changed from β-C2S to γ-C2S at the 725℃，accompanied by 11% volume expansion, which could result in pulverization phenomenon. 0ur research group firstly put forward an innovative idea that take advantage of such expansion pulverization to improve the grindability of converter slag, and the research focuses on selective formation of C2S in converter slag, phase evolution of C2S and the relation between phase evolution of C2S and self-pulverization of converter slag. In the project, the mechanism of selective formation of C2S and its structural change, and the theory of slag self-pulverization caused by C2S structural change will been studied by physical and chemical method as well as modern analytical techniques. The goal of the project is to reduce the energy consumption and improve efficiency in slag grinding process for reusing converter slag.

转炉钢渣微粉化是钢渣资源化大宗量利用的有效途径之一，然而制约钢渣微粉化的主要问题是其易磨性差。本项目申请依据于项目组前期的工作积累和发现，分析了问题存在的根本原因，提出通过促进转炉钢渣相演变和自粉化以解决此难题的新思路，研究包括转炉钢渣中硅酸二钙相（C2S）的优势析出；C2S析出相由β向γ相的演变和C2S相演变与转炉钢渣自粉化关系三个方面。研究集中在析出和演变的机理以及其实现条件等基础科学问题，运用经典的冶金、材料科学理论，结合SEM, XRD, EBSD等现代分析测试技术，来解决研究过程中遇到的科学难题。项目的目标是降低转炉钢渣粉磨耗能，改善其易磨性，为实现转炉钢渣的高效循环利用提供科学依据和相应的参数。

转炉钢渣微粉化处理是钢渣综合利用的主要途径之一，然而转炉钢渣易磨性差。本项目提出了转炉钢渣自粉化的新思路，主要研究了SiO2改质对转炉钢渣矿相变化和C2S相优势析出的影响、转炉钢渣中C2S相晶型转变的温度控制、渣中固溶离子对C2S相晶型转变的影响、SiO2改质转炉钢渣自粉化和实际转炉钢渣高温改质还原自粉化。本项目的研究结果表明，转炉钢渣自粉化效果与钢渣中C2S的含量成正比，通过SiO2改质，控制转炉钢渣碱度范围R=2.3~3.1左右，渣中C2S可优势析出，有利于钢渣实现自粉化；同时通过温度调节，可控制渣中C2S相各晶型的转变；转炉钢渣中的P、Cr、V均会抑制C2S相晶型转变，特别是转炉钢渣中P2O5含量大于0.5%时，钢渣一般不能自粉化，因此实际转炉钢渣要实现自粉化还需进一步进行还原脱磷处理，而将转炉钢渣高温熔融改质有利于还原脱磷及钢渣自粉化。通过本项目研究，可实现转炉钢渣高温改质完全还原自粉化，研究成果能大大推动转炉钢渣的微粉化及大宗量循环利用。