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研究了薄带连铸铌微合金化低碳钢的组织与力学性能,利用电子背散射技术(EBSD)标定了铁素体(贝氏体)的晶粒取向和晶界特征,并利用透射电镜(TEM)观察了铸带及热轧带钢中的析出物。结果表明:薄带连铸铌微合金化低碳钢凝固组织主要为两侧柱状晶区,中间存在一定宽度的等轴晶区。室温组织由贝氏体和少量多边形铁素体构成,小角度晶界(2°~15°)所占比例较多。铌以固溶状态存在于铸带中,热轧后碳氮化铌呈球状析出,尺寸为5~20 nm。热轧薄带组织为细小的铁素体晶粒加少量珠光体,伸长率较铸带明显提高,达到23%以上。
The microstructure and mechanical properties of niobium microalloyed mild steel for strip casting were studied. The grain orientation and grain boundary characteristics of ferrite (bainite) were determined by electron backscattering (EBSD) (TEM) The cast strip and the hot-rolled strip were observed for their precipitates. The results show that the solidified microstructure of Nb microalloyed low carbon steel in strip casting is mainly composed of columnar crystal regions on both sides and equiaxed zone with a certain width in the middle. At room temperature, bainite and a small amount of polygonal ferrite structure, small angle grain boundaries (2 ° ~ 15 °) accounted for a large proportion. Niobium exists as a solid solution in the cast strip, and the niobium carbonitride is precipitated as a sphere after hot rolling with a size of 5-20 nm. Hot-rolled strip microstructure with fine ferrite grains plus a small amount of pearlite, elongation significantly increased compared with the cast, reaching more than 23%.