热轧板翘皮缺陷的渗碳行为和组织特征

 为了提高SPHC热轧带钢的表面质量,针对异常翘皮缺陷的成因展开研究。利用光学显微镜、扫描电镜、能谱仪和硬度仪分析了缺陷处与基体的组织、成分和硬度的差异。结果表明,翘皮缺陷主要是由连铸坯中存在大量的夹杂物所致,同时这些夹杂物碳含量较高,在板坯加热过程中对周围基体起到“渗碳”作用,渗碳层厚度可达5 727.2 μm。带钢横截面的组织差异是由表面与芯部的温差所导致的动态回复与再结晶差异造成的。在层流冷却段,渗碳区域的过冷奥氏体发生了离异共析转变,粒状渗碳体均匀弥散析出。

Carburizing behavior and microstructural characteristics of hot-rolled strip at surface sliver defects

The formation mechanism of abnormal sliver defects was studied in order to improve the surface quality of SPHC hot-rolled strip. The differences in microstructure,composition and properties between the defects and the matrix were analyzed by optical microscope,scanning electron microscope,energy spectrometer and hardness tester. The results show that the defects are mainly induced by the presence of many slag inclusions in the continuous casting slabs,and these slag inclusions with a high carbon content play a role of "carburizing" on the surrounding matrix during the heating process of the slab,in which the thickness of the carburizing layer can reach 5 727.2 μm. The varied microstructure in strip cross-section is caused by the difference of dynamic recovery and dynamic recrystallization owing to the temperature discrepancy between the surface and core. During the laminar flow cooling period,the intensely distributed fine carbide particles in the carburizing region cause the divorced eutectoid transformation of the supercooled austenite in the surface layer,and the granular cementite precipitates along the grain boundaries.