美国铁精矿配比对球团冶金性能及微观显微结构的影响

Influence of Different Ratios of the United States Iron Concentrate on Metallurgical Performance and Microstructure of Pellets

摘要:

随着我国钢铁工业向集约大型化、低碳排放转型，对高炉炼铁炉料的要求不断提高。球团因高效能、低能耗及环保等优势，需求量逐渐增加。然而，国内铁矿石资源的劣势促使采用进口铁精矿制备高质量球团成为主流趋势。美国铁精矿作为新进口矿粉，虽品位低但碱性氧化物含量高，通过配加美国铁精矿粉可以改变制备球团铁矿粉的物理和冶金性能，达到提高球团冶金性能的目的。通过球团配矿实验、还原性实验、还原膨胀率实验及矿相显微镜分析，研究了不同美国铁精矿粉的配比对球团冶金性能及微观显微结构的影响，以优化配矿粉的结构、提升生球与成品球的性能。结果表明，配加美国铁精矿粉，对造球工序影响较大。随着美国铁精矿粉配比（质量分数）从0%增加至35%，造球返球率和球盘频率增大；当美国铁精矿配比为20%时，成品球团的综合质量最佳，冶金性能和抗压强度均满足高炉生产需求。随着美国铁精粉配比增加，成品球团中赤铁矿结晶发育程度逐渐降低，而镁铁矿和铁酸钙生成量逐渐增加，宏观表现为成品球团的抗压强度降低，但冶金性能得以改善。本研究为合理利用美国铁精矿粉，以及降低造球粘结剂的用量、确保生球和成品球的强度、改善球团的还原性能提供了理论依据和技术支持，有利于提升我国钢铁工业的低碳环保水平，推动行业的可持续发展。

Abstract:

As China′s iron and steel industry evolves towards intensive， large-scale， and low-carbon emission operations， the standards for furnace feedstock continually escalate. Pellet ore， owing to its efficiency， energy conservation， and environmental benefits， has emerged as a pivotal direction， with the demand for high-quality pellets steadily rising. However， the inferior quality of domestic iron ore resources necessitates the prevalent use of imported iron ore concentrate for pellet production. American iron ore concentrate， a newly imported mineral， boasts a low grade but high alkaline oxide content， and its large-scale application remains unexplored. By incorporating American iron ore concentrate， the physical and metallurgical characteristics of iron ore powder can be modulated to enhance the metallurgical properties of pellet ore. This study delves into the influence of varying ratios of the United States iron ore concentrate on the metallurgical properties and microstructure of pellet ores through a comprehensive suite of experiments， including pellet mixing， reductivity testing， reduction and expansion analysis， and mineral microscopy. The objective is to refine the mixing structure， elevate the performance of raw and finished balls， and elucidate the underlying mechanism of pellet ore formation. The results indicate that the incorporation of the United States iron ore concentrates significantly influences the ball-making process. As the proportion of the United States concentrates increases from 0% to 35%， there is a notable enhancement in ball-making and ball return rates， as well as an increase in ball disc frequency. Notably， at a 20% ratio of the United States concentrates， the overall quality of the pellet ore is optimized， satisfying the metallurgical properties and compressive strength standards required for blast furnace production. Furthermore， the elevation in the United States concentrate content leads to a gradual decrease in hematite crystal development within the pellet ore， accompanied by a rise in the formation of magnesia ferrite and calcium ferrite. This microstructural change is macroscopically manifested by a decline in compressive strength and an improvement in metallurgical performance. The findings of this study offer theoretical justification and technical guidance for the efficient utilization of the United States iron ore concentrate resources. By minimizing the amount of binding agent required for balling， ensuring the robustness of raw and finished balls， and enhancing the reducing properties of pellets， this approach contributes to elevating the low-carbon and environmentally friendly practices of China's iron and steel industry， thereby fostering its sustainable development.