PDF《博士学位论文公示材料》

―1― 博士学位论文公示材料 学生姓名 吕铭 学号

1010232 二级学科 钢铁冶金 导师姓名 姜茂发 论文题目 船板钢镁处理工艺技术开发与应用 论文关键词 船板钢;

镁处理;

洁净度;

非金属夹杂物;

技术开发与应用 论文摘要(中文) 钢液镁处理具有良好的夹杂物控制功能,开发适合于工业应用的钢液镁处理技术对于钢材洁净度 和力学性能的控制具有重要意义.

本课题结合课题依托钢铁厂宽厚板质量提升的需求,以船板钢为目 标钢种,在含镁钢液体系热力学计算与分析的基础上,通过钢液镁处理高温热态模拟实验和工业化试 验,开发出了基于 LD-LF(RH)-CC 流程的钢液镁处理关键技术并应用于工业批量生产,取得了显著的 钢水洁净度和夹杂物控制效果,为钢液镁处理技术的应用领域拓展打下了良好基础. 为指导镁处理工艺技术开发,首先开展了含镁钢液体系热力学计算与分析,结果表明,Mg 的脱 氧能力极强,当钢液中溶解镁含量为 0.001%时,溶解氧含量可以降至 0.0002%左右.对于 Fe-Mg-Al-O 钢液体系,存在 MgO、MgO・ Al2O3 和Al2O3 三个稳定区域,控制钢液中合适的溶解镁含量,可实现非 金属夹杂物的变质行为,这为镁处理工艺技术的开发奠定了理论基础. 在热力学计算的基础上,开展了钢液单独铝脱氧、单独镁脱氧和铝脱氧后镁处理热态模拟实验. 铝脱氧后镁处理可有效将钢中Al2O3夹杂变质为Mg-Al-O夹杂;

与单独铝脱氧相比,单独镁脱氧和铝脱 氧后镁处理钢中夹杂物数量显著增加,粒度显著降低,且分布更加集中于小尺寸夹杂物;

非金属夹杂 物原位观察结果表明,钢液中Al2O3夹杂易于聚合生成大尺寸簇状夹杂,而MgO和Mg-Al-O夹杂无明显 聚合行为,促使夹杂物以细小弥散化状态分布.以FH40为目标钢种的真空感应炉模拟实验结果表明, 经过镁处理,Al2O3夹杂可有效变质为Mg-Al-O夹杂,呈细小弥散化特点分布,且随着镁处理强度的增 加,变质更加完全. 在镁处理热态模拟实验的基础上,进一步开展了船板钢镁处理工业化试验.金属镁以 Mg-Al-Fe 合金铁包芯线形式喂入钢水,喂线过程平稳,未出现钢水喷溅和大翻等现象,可实现钢水化学成分的 稳定控制并符合钢种标准要求;

与钙处理工艺相比,镁处理连铸坯全氧含量显著降低,洁净度显著提 高;

钢中 Al2O3 夹杂充分变质为镁铝尖晶石夹杂,粒度显著降低. 综合热态模拟实验、真空感应炉半工业化实验和工业试验研究成果,针对BOF-LF(RH)-CC冶炼工 艺,集成了包括镁合金制备、镁合金加入与钢水成分协调控制在内的钢液镁处理关键技术并应用于船 板钢工业化批量生产.结果表明,冶炼过程平稳、钢水成分控制稳定、夹杂物呈细小弥散化分布,洁 净度控制达到历史最佳水平,成品钢板探伤合格率和弯曲测试合格率均为100%,屈服强度、拉伸强度、 延伸率和冲击功等力学性能均有不同程度改善. ―2― 论文摘要(英文) For the outstanding function of the liquid steel magnesium treatment on the inclusion controlling, further for the steel cleaness and the mechanical properties, it is of great significance for the development of magnesium treatment technology. In order to inhance the quality of the main products of the wide and heavy plate of the aimed steel plant, in this research, based on the thermodynamic calculation and analysis of the liquid steel system containing magnesium, by means of the high temperature simulation experiments and the industry experiments, the key technology of the magnesium treatment was developed about the smelting route of LD-LF(RH)-CC and was applied in industrialized mass production of the ship plate steel and the controlling effect was significant on the steel cleaness, the inclusions and the mechanical properties, which lays a good foundation for the expanding of the magnesium treatment technology. For the technology development of the magnesium treatment of liquid steel, the thermodynamic calculation and analysis of the steel system containing magnesium was conducted firstly. The results showed that, the deoxidation ability is so strong that as the dissoved magnesium content is of 0.001%, the dissolved oxygen content is of 0.0002%. For the liquid steel system of Fe-Mg-Al-O, there exist three thermodynamic stable region of MgO, MgO・ Al2O3 and Al2O3, the compositon of the inclusion in the liquid steel can be transformed by controlling the suitable content of the dissolved magnesium. On the basis of thermodynamic analysis, the experiments about single aluminum deoxidation, single magnesium deoxidation and magnesium treatment after aluminum deoxidation were conducted respectively. The results showed that, the inclusion of Al2O3 can be transformed effectively to the Mg-Al-O type inclusion. Contrasting with the single deoxidaton of alumanium, the inclusions quantity of single magnesium deoxidation and magnesium treatment after alumanium deoxidation increased significantly, and the partical size of the inclusions decreased significantly, and the distribution of the partical size is more concentrated on the smaller size zone. The in situ observation of the inclusion moving behavior results showed that, the inclusion of Al2O3 is more likely moving together to format the larger clusters, on the contrary, the inculusions of MgO and the Mg-Al-O type show no the tendency of aggregation, which is advantageous for the inclusions dispersing in the liquid steel as the tiny state. Moreover, simulation experiments via vacuum induction furnace of magnesium treatment on the FH40 ship steel were conducted, the results showed that, the inclusion of Al2O3 can be transformed effectively to the Mg-Al-O type inclusion, and with the increasing of magnesium treatment strength, the transformation of the inculusion is more completely. Based on the results of the simulation experiments, the industry magnesium treatment experiments were conducted on the ship plate steel. According to the technology of calcium treatment, the Mg-Al-Fe alloy was used as magnesium treatment agent and was fed into liquid steel as the packed wire. The results showed that, during the feeding process, there is no phenomenon of steel splashing, the steel compositions can be controlled stably, which met the requirement of steel controlling standard. The inculusion of Al2O3 can be transformed to magnesia-alumina spinel completely. Contrasting with the calcium treatment, the partical size of inclusions is ―3― tinier, the total oxygen content of the steel is decreased and the cleaness enhanced obviously. Integrating the results of the high temperature simulation experiments, the Semi industrialized experiments via vacuum induction furnace ........