C-Mn中厚钢板单向拉伸断后伸长率不合格原因分析

摘要

By means of optical microscope,scanning electron microscope,energy spectrometer,the unidirection-al tensile fracture morphology,microstructure,inclusions,grain boundary and intragranular composition are analyzed. The results show that the microscopic morphology of the fracture is dimple and cleavage. The cleavage feature appears in the central part of fracture. The elongation is increased with decrease of cleavage feature;Some parallel cracks exist at the fracture and MnS inclusions exist in the cracks. Elongation increases with downgrading of MnS inclusions rat-ings;The grain size of the steel plate with disqualified elongation is not uniform. The MnS inclusions and grain uniform-ity are the main factors influencing elongation.%采用光学显微镜、扫描电子显微镜、能谱仪分析C-Mn中厚钢板单向拉伸断口形貌、组织、夹杂物、晶界及晶内成分。结果表明，断面微观形貌均为韧窝＋解理特征。解理特征出现在断口中心部位，随解理特征减少，伸长率提高；断面均可见相互平行的裂隙，裂隙中存在MnS夹杂。MnS夹杂级数降低，伸长率也随之增大；伸长率不合格钢板的晶粒大小不均匀。据此判定，MnS夹杂和晶粒均匀性是影响伸长率的主要原因。