连铸板坯结晶器内凝固坯壳裂纹敏感性研究

Analysis of Solidified Shell Cracking Susceptibility in Slab Continuous Casting Mold

基于钢凝固两相区溶质微观偏析模型和连铸结晶器内坯壳凝固生长二维瞬态热/力耦合有限元模型,提出了定量化描述结晶器内坯壳凝固生长的裂纹敏感性预测模型---CSC(Cracking Susceptibility Coefficient)模型。通过分析结晶器内包晶钢坯壳凝固宏观热/力学行为和坯壳裂纹敏感系数分布,探究了板坯结晶器内包晶钢坯壳凝固生长过程中裂纹敏感性的变化规律。结果表明,典型包晶钢板坯连铸工况下,坯壳偏离角区域易产生"热点",引发坯壳凝固前沿脆性温度区宽度扩大,结晶器窄面线性单锥度极易破坏坯壳应力分布的均匀性;包晶钢板坯表面裂纹和皮下裂纹主要产生于坯壳凝固初期,坯壳角部皮下裂纹则在结晶器内大部分区域均可能产生。

Based on a microsegregation model of solute elements in mushy zone and a two dimensional transient thermo-mechanical coupling finite element model to describe the growth of solidifying shell in continuous casting mold, a CSC （Cracking Susceptibility Coefficient） analytical model to represent the possibility of solidification cracking of shell in mold quantitatively was proposed. The variation of shell cracking susceptibility in slab mold during a typical peritectic steel continuous casting process was investigated by analyzing the thermal and mechanical behaviors of solidified shell and the shell CSC distribution. The results show that the hot spots appear on shell off-comer and broaden the area of shell brittle temperature range under the typical peritectic steel slab continuous casting process, and the uniformity of shell stress distribution would be broken by adopting simple linear mold narrow face taper. Moreover, the shell surface cracks and subsurface cracks of peritectic steel slab mainly occur in the initial stage of shell solidification, while the comer subsurface cracks can occur at most part of the mold height.