薄带连铸铌微合金化低碳钢的组织与性能

Microstructure and Mechanical Properties on Nb Micro Alloyed Low Carbon Steel Produced by Twin-Roll Strip Casting

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 Nb micro alloyed low carbon steel strip were studied.The grain orientation and boundary characteristic of ferrite（bainitic） were investigated by using the EBSD technique.The as-cast strip and hot rolled strip were observed by the TEM.Results show that the solidification structure of the Nb micro alloyed low carbon steel is composed of two columnar zones and an equiaxed zone located in the middle of the strip.The microstructure of strip is predominantly bainite and a few polygon ferrite.The EBSD results indicate that there are large of 2°-15° low-angle grain boundaries.TEM examination has not revealed any Nb precipitation in as-cast strip,but there are globular Nb（C,N） precipitation with the size ranging from 5 to 20nm after being hot rolled.The microstructure of the hot rolled strip is consisted of fine ferrite and a few pearlite.The hot rolled strip has attractive mechanical properties.Its elongation reaches more than 23%,which is much better than the as-cast strip.