利用高分辨同步辐射Micro-CT定量三维表征含Ti铁素体不锈钢铸坯中氧化物夹杂

QUANTITATIVE 3D CHARACTERIZATION ON OXIDE INCLUSIONS IN SLAB OF Ti BEARING FERRITIC STAINLESS STEEL USING HIGH RESOLUTION SYNCHROTRON MICRO-CT

采用高分辨同步辐射计算机微断层扫描技术(Micro-CT)对含Ti铁素体不锈钢铸坯中氧化物夹杂进行了三维检测,定量分析了氧化物夹杂数量、体积和尺寸等特征在铸坯厚度方向的分布规律,并与自动扫描电镜ASPEX的二维检测结果对比.结果表明,Micro-CT能够更准确地实现钢中夹杂物的无损检测.Micro-CT检测到的氧化物基本都为球形,各位置夹杂物数量随着尺寸的增加而减少.氧化物数量密度和体积分数整体上在铸坯厚度中心最大,并随着距厚度中心的距离增加而减小,在铸坯表层附近达到最小值.而氧化物平均等效直径在铸坯表层附近最大,在内弧1/4厚度附近最小.

Non-metallic inclusions especially oxides are detrimental to the quality of ferritic stainless steel products. Accurate characterization on inclusions is conducive to further research on the inclusion control. There are some disadvantages in traditional 2D or 3D inclusion detection methods, tomography is thus employed to characterize inclusions in steel in the current work. Oxide inclusions in the slab of Ti bearing ferritic stainless steel were characterized 3 dimensionally using high resolution synchrotron micro computed tomography （Micro-CT）, and the variations of quantity, volume and size of oxide inclusions along the thickness of continuous casting slab were analyzed quantitatively and compared with the 2D results detected by ASPEX, an automated scanning SEM. It was found that non-destructive detection could be well done by Micro-CT more accurately. The detected oxides by Micro-CT were mainly global, and the number of inclusions decreased with increasing size. In general, the number density and volume fraction of oxides were largest in the center of slab thickness, and decreased with the distance from center, reached the smallest value near the surface of slab. Contrarily, the average of equivalent diameter of oxide inclusions was largest near slab surface, and was smallest near quarter of thickness on the loose side.