Q390D-Z25钢板断面收缩率不合格原因分析

Cause Analysis of Unqualified Reduction of Area of Q390D-Z25 Steel Plate

Q390D厚规格Z向钢经常出现断面收缩率不合格的情况。通过对不合格试样进行化学成分分析、宏观观察、低倍检验、金相检验及电镜能谱检验,发现发达的柱状晶和中间裂纹是导致断面收缩率不合格的主要原因。采取降低钢水过热度、二冷区采用弱冷、延长二冷区喷水长度、提高Mn/S比、选择合适铸坯拉速等措施,可有效预防铸坯发达柱状晶和中间裂纹的产生。

Q390D thick specifications Z-direction steel often has unqualified reduction of area.Through the chemical composition analysis,macroscopic observation,low magnification inspection,metallographic inspection,SEM inspection and energy spectrum inspection,it is found that columnar crystals and the intermediate crack is the main reasons for the unqualified reduction of area.Measures such as reducing the superheat of molten steel,adopting weak cooling in the secondary cooling zone,prolonging the spray length in the secondary cooling zone,increasing Mn/S ratio and selecting appropriate casting speed can effectively prevent the occurrence of developed columnar crystals and intermediate cracks in the slab.