含P耐候钢冲击不合格原因探讨

Discussion on the Impact Failure Reasons of P-containing Weathering Steel

利用扫描电子显微镜、能谱仪、光学显微镜及电子探针分析了含P耐候钢Q345NH低温冲击不合格试样,研究冲击值低的原因。试验结果表明:断裂源处解理面大小不均,有明显的混晶现象,而且与断裂源对应的截面上含有大量的MnS夹杂,组织上同时存在宽大的铁素体条带,P偏析严重。分析发现试样混晶、超标的夹杂和P偏析是导致Q345NH低温冲击不合格的主要原因。

Unqualified low temperature impact samples of P-containing weathering steel Q345NH were analyzed by means of SEM,EDS,Optical Microscope and EPMA,in order to figure out the reason of low impact value.The experimental results show that the cleavage surface at the fracture source is uneven,with clear mixed crystal phenomenon.The cross section corresponding to the fracture source contains a large quantity of MnS inclusions.There exists also a large wide ferrite banding and serious P segregation.In general,the main reasons for the low temperature impact failure of Q345NH are mixed crystals,excessive inclusions and P segregation.