铸轧薄带的边部斜裂纹形成机理

 为了控制铸轧薄带产品质量,降低铸轧工艺本征裂纹导致的断带风险,针对铸轧薄带的边部斜裂纹展开研究,提出边部斜裂纹形成的直接原因为侧封与熔池间的换热使熔池边部的Kiss点高度局部提升。该处薄带进入铸轧塑性变形阶段的初始厚度局部增大,由此引发的斜向剪应力导致了边部斜裂纹的产生。建立了熔池的热-流耦合数值仿真模型,分析了Kiss点高度沿铸轧辊宽度方向上的分布规律,结果显示熔池边部的Kiss点高度高于熔池中心。建立了热-力耦合数值仿真模型,分析了变厚度薄带热轧时其塑性变形区内的应力分布状况,结果显示斜向剪应力集中分布于后滑区边部,其方向与后滑区金属的流动方向一致。仿真结果验证了所提出的边部斜裂纹形成机理的合理性。

Mechanism of oblique edge crack formation of cast-rolling strip

In order to improve the quality of cast-rolled strip products and reduce the risk of strip breakage caused by intrinsic cracks in the cast-rolling process. The oblique crack at the edge of the cast-rolled strip was studied to derive the formation mechanism of oblique crack in the edge:the heat exchange between the side seal and the molten pool makes the Kiss point height on the side of the pool locally elevated,leading to the local increase of the initial thickness of the thin strip in the plastic deformation stage of casting-rolling. Therefore,the oblique shear stress induced in the plastic deformation zone of the thin strip becomes the main reason for the formation of the oblique crack on the edge. A thermal-flow coupling numerical simulation model was established to analyze the distribution law of Kiss height along the width of the rollers in the molten pool. The results show that the Kiss point height on the edge of the pool is higher than that near the center of the pool. A thermally-mechanical coupling numerical simulation model was established to analyze the stress distribution in the plastic deformation zone of a thin strip with variable thickness during hot rolling. The shear stress analysis shows that the oblique shear stress is concentrated on the side of the backward slip zone in the plastic deformation zone,and its direction is consistent with the flow direction of the metal in the backsliding zone. A thermal-mechanical coupling numerical simulation model was established to analyze the stress distribution in the plastic deformation zone of the thin strip with a varying thickness during hot rolling. The analysis shows that the oblique shear stress is concentrated on the edge of the backward slip zone,and its direction is consistent with the flow direction of the metal there. The above simulation results verify the rationality of the formation mechanism.