热连轧碳钢表面边部黑线缺陷分析与改进

Analysis and improvement of black line defects on surface edge of hot continuous rolling carbon steel

根据表面黑线缺陷的宏观分布和微观截面与表面光学特征,结合轧制生产线工艺与装备的跟踪与分析,明确了热连轧碳钢表面边部黑线缺陷的产生原因和形成机理。结果表明,表面边部黑线缺陷的产生与粗轧时边部金属的塑性变形有关,立辊表面质量差会促进或加重边部黑线。相对于倒角坯,直角坯的边部增厚多且温降大,更易形成黑线缺陷。通过采取优化轧制模式、缩短立辊使用周期和投入倒角坯等改进措施后,热连轧碳钢表面黑线偶有出现,且在距边部10 mm范围内,热卷边部的黑线缺陷得到了有效消除。

According to the macroscopic distribution of black line defects at surface,and the optical characteristics of microscopic cross-section and surface,combined with the tracking and analysis on the process and equipment of rolling production line,the cause and forma-tion mechanism of black line defects on surface edge of hot continuous rolling carbon steel were determined.The results show that the oc-currence of black line defects on the surface edge is related to the plastic deformation of metal on the edge during rough rolling,and the poor surface quality of vertical roller will promote or aggravate the black line on the edge.Compared with chamfered billet,the edge of right-angle billet is easy to form black line defects because of the large thickening of its edge and the large temperature drop.After the im-provement measures such as optimizing the rolling mode,shortening the service period of vertical roller and putting in chamfered billet,the black line occasionally appears at surface for hot continuous rolling carbon steel and is within 10 mm from the edge,the black line de-fects on the hot rolled edge can be effectively eliminated.