复吹转炉脱磷高效精准控制基础研究

Low cost, stable and efficient phosphorus removal in BOF is research emphasis and controlling difficulties of steelmaking field. The judgement and intervention on multiple, interacting factors affecting dephosphorization effect is still in a state of grey box, and regulation means of molten pool dephosphorization is relatively extensive, which unable to achieve precise control of dephosphorization effect. It’s need to deepen study the interaction mechanism of melting pool and dephosphorization effect. From perspective of thermodynamics and dynamics, the subject will research mixing characteristics of molten pool under interaction of multi-factors in different stage of converter steelmaking, combined with the solution (melting) and slag forming characteristics of accessories in the pool, ‘steel-slag’ interface and slag phase, through theoretical calculation, numerical and physical simulation, thermal state experiment, mathematical modeling and database development methods. The relationship between molten pool mass transfer and dynamic characteristic parameters including ‘steel-slag’ area, velocity distribution, slag metallurgical index et al. will be established, and accumulate basic data of influence of mixing efficiency on dephosphorization effect. It will establish mechanism model of the molten pool P rapid transfer, steel-slag interface P oxidation and effective conversion of 3FeO•P2O5 to nCaO•P2O5 in slag. The issue will realize key basic data of high efficiency precise control of BOF dephosphorization and fast phosphorus transformation in slag, which can provide theory and technical support on accurate control of smelting technology and further cost decreasing and benefit increasing of BOF steelmaking.

转炉吹炼时磷的低成本、高效稳定去除是炼钢领域一个研究重点和控制难点。目前对影响脱磷效果的多重、交互因素的判断和干预仍处于灰箱状态，调控熔池脱磷的手段相对粗放，无法实现对脱磷效果的精准控制，需深化熔池状态与脱磷效果的关联机理研究。本课题从热力学和动力学角度出发，用理论计算、数值与物理模拟、热态实验、数学建模及数据库开发等方法，研究转炉不同阶段多因素交互作用下的熔池搅拌特征，并结合炼钢辅料在熔池、“钢-渣”界面及渣相内分/熔解特性与成渣规律，建立熔池传质与“钢-渣”界面积、速度分布、炉渣冶金状态等动态特征参数之间的关系方程，积累熔池搅拌模式影响脱磷效率的基础数据，建立熔池中磷快速传递、“钢-渣”界面磷氧化及炉渣中3FeO•P2O5有效转变为nCaO•P2O5的机理模型。课题将探明转炉炼钢过程磷的高效、精准脱除与炉渣快速固磷的关键基础数据，对转炉冶炼技术的精准控制与降本增效提供理论和技术支撑。

本课题采用理论计算、数值与物理模拟、热态实验、数学建模等方法开展转炉脱磷相关基础研究，主要结论如下：.运用Factsage软件对100g铁水吹炼进行模拟计算，发现在吹氧0~0.56g初段为Si的烧损。当吹氧0.56~0.6g熔池Si烧损接近至痕量（10-5~10-6级）时，Si烧损速率接近0.584%/s。在吹氧量0.57~3g区间，P为线性烧损，平均烧损速率达到0.013%/s。Mn为曲线烧损，平均烧损速率达到0.00135%/s。在吹氧量0.6~3g区间内，C为线性烧损，平均烧损率为0.48%/s。.数值模拟发现，顶吹射流对熔池的搅拌能力有限，底吹气流对熔池及钢渣界面的两相作用搅拌超过90%。随着底吹强度增大至0.20Nm3/(min·t)，熔池中的气体相所占比例呈递增的趋势，熔池内部整体流动速度提升，钢液内部的对流传质、传输流动性好，有利于促进钢液中磷在钢-渣界面反应。随着底吹强度的加大，相界面面积逐渐增加，“死区”面积减少。底吹流量超过0.10Nm3/(min·t)时炉底的侵蚀作用加剧。.水模拟实验发现，水-油间的乳化主要依赖顶吹，乳化层的厚度随顶吹时间的增加而增加。混匀时间随着底吹强度的增加逐渐下降并趋于稳定。提高底吹强度至0.30Nm3/(min·t)时，混匀时间可缩短至72.5%。在底吹强度为0.08~0.15Nm3/(min·t)时，搅拌条件较好。.热态实验发现，辅料熔化时过渡层物相为：CaO基体→CaO-FeO层→C2S-C3P固溶体→CaO-SiO2-FeO→渣基体。在反应界面形成一层C2S-C3P固溶体层。随着反应进行，C2S-C3P固溶体的磷含量先增加后减少，PO43-被石灰固化，但同时生成新的C2S固溶体阻碍反应进一步进行。钢中[P]含量与[C]含量呈正相关趋势，脱磷过程表观磷分配比与炉渣碱度呈明显的正相关趋势。.本项目基本完成预研任务，达到预期目标。