微合金钢薄板坯连铸边角裂纹控制  

Corner crack control for thin slab continuous casting of microalloyed steel

作　　者：蔡兆镇 朱苗勇 CAI Zhao-zhen;ZHU Miao-yong(School of Metallurgy,Northeastern University,Shenyang 110819,China)

机构地区：[1]东北大学冶金学院,沈阳110819

出　　处：《工程科学学报》2022年第9期1548-1557,共10页Chinese Journal of Engineering

基　　金：国家自然科学基金资助项目(52174307,51774075,51404061);兴辽计划资助项目(XLYC1802032)。

摘　　要：微合金钢薄板坯连铸过程高发边角部裂纹,致使热轧卷板边部产生翘皮、烂边等质量缺陷,是钢铁行业的共性技术难题.本文立足于某钢厂QStE380TM低碳含铌钛微合金钢薄板坯连铸生产,检测分析了铸坯角部组织金相结构与碳氮化物析出特点、不同冷却与变形速率条件下钢的断面收缩率,并数值仿真研究了不同结构结晶器和二冷区铸坯温度与应力的演变规律.结果表明:微合金钢薄板坯连铸过程存在明显的第三脆性区,且变形速率越大,第三脆性区越显著.传统薄板坯连铸工艺条件下,结晶器的中上部及其出口至液芯压下段的二冷高温区,铸坯角部冷速较低,致使其组织晶界含铌钛微合金碳氮化物呈链状析出.铸坯在液芯压下过程,低塑性角部因受较大变形与应力作用而引发裂纹缺陷.实施沿高度方向有效补偿坯壳凝固收缩的窄面高斯凹型曲面结晶器及其足辊区超强冷工艺,可分别提升铸坯角部冷速至10和20℃·s^(-1)以上,从而促使铸坯角部组织碳氮化物弥散析出,并促进铸坯窄面在液芯压下过程金属宽展流动而降低角部压下应力,大幅降低了微合金钢薄板坯边角部裂纹发生率.Thin slab continuous casting and rolling process is an important way to produce hot-rolled strips.Recently,the process has been widely used to produce Nb/V/Ti/B bearing microalloyed steel.However,during the continuous casting of the thin slabs of the microalloyed steel,there are frequent cracks on the corners of the slabs,which would cause quality defects,such as scars and cracks at the edges of the hot-rolled coils.These defects are a common technical issue in the steel industry.In this paper,the characteristics of the microstructure and carbonitride precipitation of the thin slab corner of QStE380TM low carbon niobium–titanium bearing microalloyed steel,as well as the reduction of area of the steel under different cooling and tensile rates,were detected.Moreover,the evolutions of the temperature of the solidified shell in different structure molds and secondary cooling processes,as well as the stress of the thin slab surface during liquid core reduction,were numerically simulated.The results show that there is a significant third brittle temperature zone during continuous casting of microalloyed steel thin slabs,and the greater the deformation rate of the thin slab,the more significant the third brittle temperature zone is.Under the conventional thin slab continuous casting process,the cooling rate of the thin slab corners in the upper part of the mold and the secondary cooling zone from the mold exit to the liquid core reduction segment is lower than 5°C·s^(-1),which is the key factor to lead a chain of niobium–titanium carbonitrides precipitate at the grain boundaries of the corners.As a result,the plasticity of the thin slab corners is greatly reduced.During the process of liquid core reduction,the low plasticity corners of the thin slab crack because of large deformation and stress.Applying the Gaussian concave curved surface mold,which the narrow face copper plates could efficiently compensate the shell shrinkage,the narrow face-foot roll zone hard cooling process can increase the cooling rates of th

关 键 词：微合金钢 薄板坯连铸 角部裂纹 结晶器 液芯压下 强冷却 

分 类 号：TF777.7[冶金工程—钢铁冶金]