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针对国内某钢厂利用电炉→LF→VD流程生产的亚包晶钢Q345B铸坯及轧材表面存在大量缺陷的现状,利用光学显微镜、扫描电镜以及能谱分析仪对铸坯表面裂纹进行了分析,并对析出物进行热力学计算,以此来分析出该钢种的铸坯产生裂纹的原因。研究结果表明:裂纹附近存在脱碳层及铁素体膜;裂纹处发现P、S富集及Al、Mg、Ca、Si等元素的夹杂物破坏了钢基体的连续性;保护渣及析出物对铸坯表面质量影响严重。为了防止缺陷的发生,应将钢水过热度控制在15~30℃;将结晶器中液渣层控制在8.5~9 mm并提高析晶相比率。同时,将钢水中氮含量稳定控制在35×10-6~45×10-6,并且适当提高Ti处理效率,降低AlN数量,对改善连铸坯表面质量有着很大的作用。
Aiming at the present situation that a certain steel mill in China produced the sub-peritectic steel Q345B slab and the surface of the rolling stock produced by the electric furnace → LF → VD process, the surface cracks of slab were analyzed by optical microscope, scanning electron microscope and energy spectrum analyzer , And the thermodynamic calculation of precipitates, in order to analyze the reasons for the steel slab cracks. The results show that there is a decarburized layer and ferrite film near the crack. The inclusions of P, S enrichment and Al, Mg, Ca, Si and other elements in the crack damage the continuity of the steel substrate. The flux and precipitates The slab surface quality has a serious impact. In order to prevent the occurrence of defects, the degree of superheating of the molten steel should be controlled at 15 ~ 30 ℃; liquid slag layer control in the mold 8.5 ~ 9 mm and improve the crystallization ratio. At the same time, the nitrogen content in the molten steel should be controlled at 35 × 10-6 ~ 45 × 10-6 steadily, and the Ti treatment efficiency and the amount of AlN should be properly increased to improve the surface quality of the slab.