SS400热轧钢板拉伸试验分层断口的显微分析

对SS4 0 0热轧钢板拉伸试验出现的断口分层进行了分析。用扫描电镜分别对断口、断口磨面以及平行于拉伸方向、垂直于钢板表面的剖面进行了显微观察 ,发现分层现象与试样中超长的带状组织密切相关。用能谱仪对断口分层处和超长铁素体带上的夹杂物进行了成分分析 ,证实均为硫化物。试样拉伸时在铁素体带上密集分布的硫化物处产生大量微裂纹 ,同时超长铁素体带的变形又受到阻碍 ,导致该处在试样拉断之前裂纹已经贯通 ,最终在断口上形成分层。因此 ,拉伸试验断口出现分层的原因是试样中存在密集分布的硫化物和超长的带状组织

MICROSCOPICAL ANALYSIS ON LAYER TENSION FRACTURE OF SS400 HOT-ROLLING STEEL PLATE

The sample with layer tension fracture made from SS400 hot-rolling steel plate was analyzed. The fracture ground face and the sections parallelling to tension direction and perpendicular to plate surface were surveyed with scanning electron microscope. It was discovered that layer fracture was concerned with super-length banded structure in the sample. The compositions of inclusions located in fracture layer zone and on the super-length ferrite band was analyzed by EDX. It was confirmed that they are sulfide. The sulfide crowded together and located in super-length ferrite band which resulted much fine crack during tension test. That the deformation of ferrite band was checked resulted the cracks gathering before the sample ruptured. Finally layer fracture was formed. It can be known that the layer tension fracture was resulted by the crowded sulfides and super-length banded structure located in the sample.