Q420B钢伸长率不合格原因分析

针对Q420B钢板在轧制后出现伸长率批量不合格的情况,通过金相检测、扫描电镜等方式对其拉伸试样进行断口形貌、组织结构、夹杂物分析。结果表明,断口部位存在较多孔隙、分层以及较严重的带状组织,裂纹及孔隙主要沿偏析组织萌生扩展;断口部位夹杂物集中分布,且呈连续性、长条状分布,其在拉力作用下和基体界面分离、扩展后最终形成裂纹,是造成钢板轧后伸长率不合格的主要原因。

Causes Analysis of the Unqualified Elongation of Q420B Steel

To the problem of unqualified elongation of rolled Q420B steel, the fractography, microstructure and inclusions of the tensile specimens were studied by optical microscopy and scanning electron microscopy. The results showed that lots of pores, serious stratification and band structure existed in the fracture site, and the initiation and growth of the cracks and pores happened at segregated band. Inclusions were concentrated on the fracture site. The inclusions beseparated and extended from matrix interface under tension, which will result in crack at last under tension. So the band structures and inclusions were thought to be the major causes of the unqualified elongation of the plate steel.