硅对高频燃烧红外吸收法测定高硅样品中碳和硫的影响

Influence of silicon on determiantion of carbon and sulphur in high silicon sample by high frequency combustion infrared absorption method

利用扫描电镜(SEM)和能谱仪(EDS)观测了经高频感应炉燃烧后高硅样品熔体中硅的存在形态和组成,从不同角度考察了样品中硅对熔融效果产生的影响,以及对高频感燃烧红外吸收法测定碳和硫结果的影响。结果显示:仅使用纯钨做助熔剂时,含硅样品熔体中的硅主要以球状的二氧化硅颗粒镶嵌于氧化钨和氧化铁等基体中,硅的存在使得高频燃烧红外吸收法测定碳和硫的准确度变差,且随着样品中硅含量的增加,这种影响的程度逐步增大。通过对影响机理进行分析认为:生成的二氧化硅使得熔体的流动性变差,且接受电磁感应形成感应电流的能力也同时减弱,从而对测定结果的精密度和正确度造成影响。实验在使用钨助熔剂的基础上,进行了添加纯锡或纯铁助熔剂的试验,结果表明:添加一定量纯锡或纯铁助熔剂,可以降低样品熔点,提高熔池温度,大大改善熔融效果,从而提高碳和硫测定的精密度和正确度。

The existence form and composition of silicon in melted high-silicon sample after combustion in high frequency induction furnace were observed by scanning electron microscope(SEM)and energy disperse spectroscopy(EDS).The influence of silicon in sample on the melting effect was investigated from different points of view.Moreover,the influence of silicon on the determination results of carbon and sulfur by high frequency combustion infrared absorption method was also investigated.The results indicated that silicon in sample melt was mainly embedded in matrix such as tungsten oxide and iron oxide in the form of spherical silicon dioxide particles when only pure tungsten was used as flux.The presence of silicon worsened the determination accuracy of carbon and sulfur by high frequency combustion infrared absorption method.Moreover,this influence gradually increased with the increase of silicon content in sample.Based on the analysis of influence mechanism,the generated silicon dioxide worsened the flowability of melt.Moreover,the ability to form induced current by electro-magnetic induction was also weakened.As a result,the precision and accuracy of determination results were influenced.Based on the use of tungsten flux,the test was conducted by addition of pure tin or pure iron flux.The results showed that the melting point of sample could be reduced and the molten pool temperature could be enhanced by adding certain amount of pure tin or pure iron flux thus greatly improveing the melting effect.As a results,the determination precision and trueness for carbon and sulfur was improved.