火花源原子发射光谱法检测钢中硫元素时分析精度降低的原因探究和问题改善

Reason Exploration and Problem Improvement of Analytical Precision Reduction in Detection of Sulfur in Steel by Spark Source Atomic Emission Spectrometry

为解决按照标准方法GB/T 4336-2016和GB/T 14203-2016检测钢中硫元素时分析精度满足标准规定,但会随着钢中锰含量的增加显著下降的问题,用扫描电子显微镜(SEM)探究原因,通过优化火花源直读光谱仪的分析通道、激发参数以及铁参比线等改善问题。样品表面经清洁、铣削后,采用标准方法GB/T 4336-2016重复分析锰质量分数分别为2.00%和0.043%的标准样品(标样1~#和标样2~#)各5次,标样1~#中硫元素测定值的相对标准偏差(2.5%)显著大于标样2~#中硫的(1.2%),可能与标样1~#中硫化物为硫化锰且在夹杂物中分布不均匀有关。为改善这一问题,调整了如下参数:预燃时间为6 s、曝光积分时间为1 s、分析通道为S1,参比线为Fe 136.137 nm。结果显示,硫元素工作曲线的线性范围为0.001 0%~0.117%,检出限为0.000 06%;方法用于锰质量分数为2%样品的分析,测定值的相对标准偏差(n=6)小于1.0%,且测定值和碳硫仪所得结果一致。

In order to solve the problems that the analytical precision met the standard requirements when detecting sulfur in steel according to the standard methods GB/T 4336-2016 and GB/T 14203-2016 while it would decrease significantly with the increase of manganese content in steel, scanning electron microscopy(SEM) was used for exploring reasons, and optimization of the analysis channel, excitation parameters and iron reference line of spark source direct reading spectrometer was used for improving questions. After the sample surface was cleaned and milled, the standard method GB/T 4336-2016 was applied to 5 replicate analysis of standard samples(standard sample 1with manganese mass fraction of 2.00% and standard sample 2with manganese mass fraction of 0.043%). RSD(2.5%) of the determined values of sulfur element in standard sample 1was significantly greater than that(1.2%) in standard sample 2, which might be related to the fact that the sulfide in standard sample 1was manganese sulfide and manganese sulfide was unevenly distributed in the inclusions. The following parameters were adjusted to improve the above problems: the prespark time was 6 s, the exposure integration time was 1 s, the analysis channel was S1, and the reference line of iron element was 136.137 nm. It was shown that the linear range of the working curve of sulfur was found in the range of 0.001 0%-0.117%, with detection limit of 0.000 06%. This method was applied to analysis of the sample with manganese mass fraction of 2%, RSD(n=6) of the determined values was less than 1.0%, and the determined values were consistent with those obtained by the carbon sulfur analyzer.