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考虑到低合金钢试样加入钨锡助熔剂后试样燃烧释放完全,其坩埚内部比生铁试样埚底光滑,埚壁迸溅少,且二次坩埚的成本更低,故选择分析完低合金钢的坩埚作为二次坩埚用于磷铁中碳和硫的分析.实验表明,在二次坩埚中加入 0.40~0.55 g试样、1.2~1.3 g钨锡助熔剂,无需空白校正即可实现高频燃烧红外吸收法对磷铁中碳和硫元素的同时测定.由于磷铁标准样品较少,不足以覆盖所有磷铁中碳或硫的含量范围,所以通过将低合金钢标准样品和磷铁标准样品ZBT384进行两两混合(总质量控制在(0.5±0.05)g之间)以配制校准样品系列.结果表明,碳在质量分数为0.05%~0.65%范围内,硫在质量分数为0.005%~0.14%范围内的校准曲线线性关系良好,碳和硫的相关系数分别为0.999 6和0.999 5.将实验方法应用于磷铁实际样品分析,测得碳和硫的相对标准偏差(RSD,n=7)分别为2.0%和3.5%.按照实验方法对磷铁标准样品和内控样品进行测定,测得结果与认定值或参考值的绝对误差均小于国家标准方法YB/T 5339-2015或YB/T 5341-2015要求的允许差.

The low alloy steel sample could be combusted and released completely after addition of tungsten-tin flux.The crucible after analysis of low alloy steel sample was smoother and the splashing was less than that of pig iron sample.Moreover, the cost of secondary crucible was lower.Therefore, the crucible after analysis of low alloy steel sample was selected as secondary crucible for analysis of carbon and sulfur in ferrophosphorus.After 0.40-0.55 g of sample and 1.2-1.3 g of tungsten-tin flux were added into secondary crucible, a simultaneous determination of carbon and sulfur in ferrophosphorus by high-frequency combustion infrared absorption method could be realized without blank correction.There were only few certified reference materials of ferrophosphorus, which could not cover the content range of carbon or sulfur in all ferrophosphorus samples.As a result, the calibration sample series were prepared by mixing certified reference materials of low alloy steel and ferrophosphorus ZBT384 with total mass in range of (0.5±0.05)g.The results indicated that the linear relationship of calibration curves was good for carbon with mass fraction in range of 0.05%-0.65% and sulfur with mass fraction in range of 0.005%-0.14%.The correlation coefficient was 0.999 6 and 0.999 5 for carbon and sulfur, respectively.The proposed method was applied to the analysis of ferrophosphorus actual sample.The relative standard deviation (RSD, n=7) was 2.0% and 3.5% for carbon and sulfur, respectively.The certified reference material and internal control sample of ferrophosphorus were determined according to the experimental method.The absolute errors between the found results and the certified or reference values were less than the allowance difference in national standard method YB/T 5339-2015 or YB/T 5341-2015.