SMA490BW耐候钢中析出相和夹杂物的定量统计分析

利用物理化学相分析的方法,结合扫描和透射电镜,研究了SMA490BW耐候钢中析出相和夹杂物的组成、形貌、尺寸信息。相分析结果显示耐候钢中存在富Cu相、M₃C、M(C,N)、非金属夹杂等,其中M₃C在耐候钢中占比为0.868%,M(C,N)占比为0.0396%;析出相平均尺寸为78.2nm,中间尺寸为51.7nm,小于100nm的约占74%,18~36nm的析出相分布最多,占总量的22.1%。扫描电镜结果显示耐候钢中夹杂物主要有3类:A类(硫化物类)夹杂;DS(单颗粒球状)类夹杂,由Al₂O₃和CaO组成的氧化物夹杂;D_Dup(球状复相夹杂)类复相氧硫化物夹杂。采用透射电镜观察了耐候钢中析出相的形貌,统计了析出相尺寸,结果显示析出相主要是碳氮和铌钛钒组成的化合物,呈圆球状、棒状、不规则形状析出;析出相尺寸从纳米级到微米级,在18~36nm范围分布最多。对比透射电镜和相分析这两种方法对析出相的统计结果,相分析能更精确地统计整个样品区域及跨尺寸范围析出相的分布情况。

Quantitative and statistical analysis of precipitation phases and inclusions in SMA490BW weathering resistant steel

The composition, morphology and dimension of precipitation phases and inclusions in SMA490BW weathering resistant steel were studied by means of physical and chemical phase analysis methods combined with scanning electron microscope (SEM) and transmission electron microscope (TEM). The results of phase analysis showed that there were Cu-rich phase, M₃C, M(C,N) and non-metallic inclusions in weathering resistant steel. The proportion of M₃C phase and M(C,N) phase was 0.868% and 0.0396%, respectively. The average size of precipitation phase was 78.2nm with intermediate size of 51.7nm. The precipitation phases with size less than 100nm accounted for about 74%. Meanwhile, the phase distribution in range of 18-36nm was most, which accounted for 22.1%. The results of SEM showed that there were three types of inclusions in weathering resistant steel: Class A (sulfide) inclusions; DS inclusions consisting of alumina oxide and calcium oxide; D_Dup inclusions consisting of composite oxygen sulfide. The morphology of precipitation phases in weathering resistant steel was observed using TEM and the statistic size of precipitation phases was analyzed. The results indicated that the precipitated phases were mainly compounds composed of carbon, nitrogen, niobium, titanium and vanadium, which were spherical, rod-shaped and irregular. The size of precipitation phases varied from nanometer to micrometer with most distribution in range of 18-36nm. The statistical results of TEM and phase analysis were compared. It was found that the phase analysis method could more accurately calculate the precipitation distribution in the whole sample area and different size range.