S355G7+M-Z35 Z向性能不合格原因分析

Reasons analysis on unqualified Z-direction property of S355G7+M-Z35 steel plates

针对70 mm厚S355G7+M-Z35钢连续出现几批Z向性能偏低的情况,通过金相检验、扫描电镜及能谱分析等方法对其Z向性能不合格原因进行了研究。结果表明,Z向性能不合格的主要原因是钢板心部存在着疏松孔洞,成为断裂源。并且在不合格试样断口处存在着较多的块状(Nb,Ti)C聚集和MnS夹杂,中心偏析处还存在贝氏体等硬相组织,更加剧了断裂扩展,导致Z向性能不合格。

According to unqualified Z-direction property of batches of 70 mm thickness S355G7 ＋ M-Z35 steel, the causes were analyzed by metallographic analysis, sanning electron microscope observation and energy spectrum analysis. The results show that the main reason for unqualified Z- direction property is porosity in the center of the steel that forming source of the crack. There are many bulk （Nb, Ti）C and MnS inclusions at the fracture of the disqualified workpieces. Hard phases such as bainite also appear at the segregation, which aggravate the fracture expand, so resulted in the disqualified Z- direction property.