采用化学成分分析、断口分析、金相检验、夹杂物分析等方法，研究了桥梁用大展宽比薄规格钢板低温冲击性能不合格的原因。结果表明：铸坯中心偏析，轧后冷却时产生了马氏体，且钢中存在粗大的MnS夹杂物，导致钢板的低温冲击性能不合格。提高钢板低温冲击性能的方法包括，在炼钢过程中，降低C、Mn、P、S等元素的含量、降低钢水过热度、在凝固末端采用强冷技术等；在轧钢过程中，提高加热温度、延长加热时间、优化道次压下量分配、降低终轧温度等。

The reasons for the unqualified low temperature impact performance of large aspect ratio thin steel plate for bridges were studied using methods such as chemical composition analysis, fracture analysis, metallographic examination, and inclusion analysis. The results show that the central segregation of the slab, the formation of martensite during cooling after rolling, and the existence of coarse MnS inclusions in the steel led to unqualified low temperature impact properties of the steel plate. The methods to improve the low temperature impact performance of steel plates included reducing the content of elements such as C, Mn, P, and S during the steelmaking process, reducing the superheat of molten steel, and using strong cooling technology at the solidification end. During the steel rolling process, increasing the heating temperature, extending the heating time, optimizing the distribution of pass reduction, and reducing the final rolling temperature are necessary.