基于扫描电镜测量非金属夹杂物分类方法探讨

Discussion on the classification rule for the nonmetallic inclusions measured by scanning electron microscope

基于扫描电镜检测夹杂物元素设置时是否计入O元素和N元素以及不同成分的夹杂物硬度相关研究较少,但其对夹杂物分类非常重要,基于此实验利用扫描电镜自动测量分析低碳钢中夹杂物含量,分别统计计入和不计入O元素和N元素时,各种类型夹杂物的成分含量变化规律,并选择典型的夹杂物进行Mapping,分析O元素、N元素及合金元素在夹杂物中的分布特点,最终依据元素的含量和分布特点,确定测试时是否应计入O元素和N元素以及不同类型夹杂物的成分分类标准。利用纳米压痕对夹杂物硬度进行表征,分析成分变化对夹杂物硬度的影响。实验结果表明Mg、Al、Ca、Mn、S元素具有较高的检测分辨率,质量分数不小于2%时,可确认该元素存在并依据其检测结果进行分类;N元素测量误差较大,分类时不可计入。此外,夹杂物硬度研究结果表明,夹杂物硬度与其成分密切相关,氧化物夹杂物硬度最大可达25 GPa;MnS硬度在3.5~4.5 GPa之间。结合夹杂物成分定量与Mapping结果,建议了不同类型夹杂物的分类准则。

During the detection of inalusions by scanning electron microscope(SEM),there are few reports on the following settings:wether O and N are counted or not;the hardness of inclusions with different composition.However,these factors are very important for the classification of inclusions.The content of inclusions in low carbon steel was automatically measured and analyzed by scanning electron microscope.The changing law of composition(content)in various types of inclusions was investigated when the elements of O and N were counted and not counted,respectively.Some typical inclusions were selected for Mapping to analyze the distribution characteristic of O,N and alloying elements in inclusions.Finally,according to the content and distribution characteristic of elements,it confirmed that whether the elements of O and N should be counted and not,and confirmed the composition classification standard for various types of inclusions.The hardness of inclusions was tested by nanoindenter.The influence of composition change on the hardness of inclusion was discussed.The experimental results indicated that the elements including Mg,Al,Ca,Mn and S had high detection resolution.When the mass fraction was not less than 2%,the presence of such element could be confirmed and its classification could be conducted according to the detection results.The measurement error of N was relatively large and it was not counted in classification.In addition,the harness testing results of inclusions indicated that the hardness of inclusion was closely related to the composition.The hardness of oxide inclusion was highest,which was up to 25 GPa.The hardness of MnS was in range of 3.5-4.5 GPa.According to the quantitative analysis of composition in inclusion and Mapping results,the classification principle for various types of inclusions was proposed.