Q345板坯表面横裂纹热轧过程演变行为

Evolution behavior of transverse cracks on Q345 slab surface during hot rolling process

在连铸生产过程中,由于化学元素、温度、机械应力等多方面因素影响,铸坯不可避免会产生表面横裂纹。轧制过程中,铸坯表面横裂纹会进一步放大影响到后续轧材的表面质量,甚至导致产品报废。为此,针对Q345钢表面横裂纹热轧过程演变行为展开研究,在铸坯表面预制“V”形裂纹进行实验室热轧试验,并建立相应轧制模型,通过试验验证模型正确性。采用现场板坯轧制工艺建立Q345钢表面不同宽度(1、2、3 mm)横裂纹轧制模型,分析不同宽度裂纹热轧过程演变特性。结果表明,宽度1 mm裂纹轧制过程出现了表面贴合的现象,而宽度2、3 mm裂纹两侧逐渐展开最后暴露到轧材表面;通过分析裂纹尺寸及高宽比变化可以发现,轧制过程不同宽度裂纹的展开宽度呈线性增加,轧制结束后,1、2、3 mm宽度裂纹展开宽度分别达到了30、32、34 mm,而裂纹深度在轧制初期减小明显,后几个道次减小量不大;不同宽度裂纹高宽比变化趋势与裂纹深度变化趋势相同,轧制初期变化量较大,轧制后几个道次高宽比趋近于0。研究结果可为优化轧制生产工艺提供理论参考。

In the continuous casting production process,due to influence of chemical elements,temperature,mechanical stress and other factors,the casting billet will inevitably produce surface transverse cracks.During the rolling process,surface transverse cracks of the casting billet will further amplify,which affects the surface quality of the subsequent rolled products,and even cause the product to be scrapped.Therefore,the evolution behavior of Q345 steel surface transverse crack in hot rolling process was studied,and the laboratory hot rolling experiment was carried out on the prefabricated"V"crack on the billet surface.The corresponding rolling model was established,and the correctness of the model was verified by the experiment.The on-site slab rolling process was used to establish the transverse crack rolling model with different widths(1,2,3 mm)on the Q345 steel surface,and evolution characteristics of cracks with different widths in hot rolling process were analyzed.The results show that the surface bonding phenomenon occurs during the rolling process of cracks with width of 1 mm,while the two sides of cracks with width of 2 mm and 3 mm gradually unfold and finally expose to the surface of the rolled material.By analyzing the change of crack size and aspect ratio,it can be found that the unfolding width of crack with different widths in the rolling process increases linearly,and the unfolding width of 1,2 and 3 mm width cracks reaches 30,32 and 34 mm after rolling,respectively,while the crack depth decreases obviously in the early stage of rolling,and decreases little in the next few passes.The change trend of aspect ratio of crack with different widths is the same as the change trend of crack depth,the initial change is large,and crack aspect ratio in the next passes tends to be 0.The research results can provide a theoretical reference for optimizing the rolling production process.