球墨铸铁试棒拉伸断口灰斑缺陷分析  

Analysis of Gray Spot Defects on Tensile Fracture Surfaces of Nodular Iron Test Bars

作　　者：刘铭 李小娟 王其 张君 林磊 LIU Ming;LI Xiao-juan;WANG Qi;ZHANG Jun;LIN Lei(Xixia Intake&Exhaust Manifold Co.,Ltd.,Xixia 474500,China)

机构地区：[1]西峡县内燃机进排气管有限责任公司,河南西峡474500

出　　处：《现代铸铁》2024年第6期41-44,共4页Modern Cast Iron

摘　　要：对硅钼球墨铸铁和高镍球墨铸铁试棒拉伸断口中出现的“灰斑区”进行了金相组织分析和扫描电镜分析,最后指出:硅钼球墨铸铁为铁素体基体,试棒断口边缘的灰斑并非铸造缺陷,而是韧窝形貌,韧窝对光发生散射作用,使得对光的反射作用减弱,故呈现暗灰色,是试棒断口的正常形貌,对力学性能并无影响;高镍球墨铸铁为奥氏体基体,一般情况下不发生解理断裂,往往为韧性断裂,整个断面颜色一致为浅灰色,试棒断口边缘的灰斑往往为氧化夹渣缺陷,会导致试棒力学性能下降,致使试棒力学性能不合格。A comprehensive investigation was conducted on the gray spot areas observed on the tensile fracture surfaces of silicon-molybdenum nodular iron and high-nickel nodular iron test bars using metallographic analysis and scanning electron microscopy(SEM).The results indicated that,the silicon-molybdenum nodular iron featured a ferritic matrix,where the gray spots located at the fracture edges were not casting defects but were attributed to dimple morphology.These dimples scattered incident light,thereby reducing reflectivity and resulting in a dark gray appearance.This feature represented a normal fracture surface morphology and did not adversely affect the mechanical properties of the material.Conversely,the high-nickel nodular iron,characterized by an austenitic matrix,typically underwent nodular fracture rather than cleavage fracture.The entire fracture surface generally exhibited a uniform light gray color.However,the gray spots at the edges of the fracture surface were often associated with oxidation inclusions,which could lead to a reduction in the mechanical performance of the test bars,potentially causing non-compliance with the required mechanical standards.

关 键 词：球墨铸铁 灰斑 韧窝 

分 类 号：TG255[金属学及工艺—铸造]