49亚包晶钢铸坯表面纵裂纹影响因素研究.docVIP

亚包晶钢铸坯表面纵裂纹影响因素研究 张乔英，曹天明，焦兴利，王越，钱海帆，张建平 （马鞍山钢铁股份有限公司，安徽省,马鞍山，243000） 摘要：采用扫描电镜、显微镜等对亚包晶钢铸坯表面纵裂纹的形貌、晶粒组织、裂纹内夹杂物和裂纹形成机理进行分析研究，发现大多数的纵裂纹发生在浸入式水口出口周围的钢水剧烈运动区域纵裂纹在结晶器内形成，形成部位是在坯壳以下~5mm低熔点区裂纹沿树枝晶臂延伸扩展，随着拉速的增加，的发生率呈上升趋势内弧表面外弧面Factors Affecting Slab Surface Longitudinal Crack of Hypo—Peritectic Steel ZHANG Qiao-ying, CAO Tian-ming, JIAO Xing-li, WANG Yue, ZHANG Jian-ping, QIAN Hai-fan (Maanshan Iron Steel Co. Ltd. Anhui, Maanshang, 243000, China) Abstract: The appearance, grain structure of longitudinal crack and non-metallic inclusions in the longitudinal crack of hypo-peritectic steel slabs were investigated with SEM and microscope method. It was found that, longitudinal cracks occurred at turbulent area around port of SEN (submerged entry nozzle).Longitudinal cracks formed in mold, and the short longitudinal crack in dendrite crystal formed on the surfaces (3~5mm from surfaces) of slabs. The cracks extended along the dendritic crystals branches, there were two kinds of fracture type, one was intergranular fracture, and the other was transgranular fracture. Effect factors on longitudinal crack, casting speed，superheat temperature，ratio of manganese and sulphur，average heat flux and mold level fluctuation were discussed. It was found that high superheat temperature and strong secondary cooling might cause longitudinal cracks on the slab surface, High casting speed tended to form cracks. Inner curved surface of strand was easier to form longitudinal cracks than outer curved surface of strand under the same casting speed. The longitudinal cracks were promoted by uneven average heat flux of mold. Key words: Hypo-Peritectic steel；slab；longitudinal crack 1 前言 含碳0.09%～0.17%的亚包晶钢由于其本身特有的凝固特性，对表面裂纹的产生、粗糙表面的形成、极为敏感，严重影响产品质量、生产组织和铸机生产能力的发挥。国内外许多钢厂连铸板坯时，尽量避开这一碳含量区域[]。表Table 1 Chemical composition of Q23501 steel 钢种 C（％） Si（％） Mn（％） P（％） S（％） Q23501 内控范围 0.14-0.17 0.15-0.13 0.4-0.6 ≤0.025 ≤0.015 目标值 0.15 0.20 0.46 ≤0.02 ≤0.01 本文结合马钢第四钢轧总厂新铸机实际生产Q23501情况，分析讨论亚包晶钢铸坯产生表面纵裂纹的影响