应用脉冲熔融法和感应热抽取法探讨钢中超低氢分析“零峰值”问题

Discussion on “zero peak” problem of ultralow hydrogen analysis in steel by impulse-heating fusion and induction-heating hot extraction

应用脉冲熔融法测定钢中超低氢,仪器显示值为"0.0μg/g"。实验对该"零峰值"现象进行了系统的研究和探讨,结果发现如果将现用石墨套坩埚换成单坩埚于同样条件下检测,可见到明显的氢峰,然而,用内控标样10点分析,确认此峰为单坩埚产生的干扰峰;尝试换用添加浴料的技术手段解决问题未能成功。转机源于另一台不同原理的同类仪器,应用感应热抽取法仪器测定数百个"零峰值"样品,可见稳定的氢峰,峰值落在0.1~0.4μg/g范围内。以力可502-457钢中氧氮氢联标样(氢认定值为(0.9±0.4)μg/g)和阿尔法AR546钢中氢标样(认定值为(0.63±0.2)μg/g)标定,线性良好数值可信。采用感应热抽取法分析内控钢中氢标样,测定值与认定值(0.5±0.2)μg/g基本一致,平行测定10次的标准偏差(SD)为0.07μg/g。分别采用脉冲熔融法和感应热抽取法对添加稀土和未添加稀土钢样品中超低氢进行分析对比试验,结果表明:对于添加稀土钢样品中氢的分析,基于脉冲熔融法的两台仪器分析均显示"0.0xμg/g";基于感应热抽取法仪器分析可知氢测定值在0.4μg/g附近;对于未添加稀土钢样品,两种方法所用的仪器分析所得氢测定值基本一致。由此分析认为:添加稀土可以造成对钢中氢分析的负干扰,对于感应热抽取法此干扰值甚微,可忽略;而对于脉冲熔融法,可见的氢分析负干扰值在0.2~0.4μg/g范围内。综上所述,对氢质量分数小于0.4μg/g的钢中超低氢分析,不宜使用脉冲熔融法;对0.4~0.9μg/g钢中超低氢分析,慎重应用脉冲熔融法;感应热抽取法样品始终保持固态,避免了因挥发所产生的负干扰,实验中未出现"零峰值"现象,适合于钢中超低氢分析。

'0.0μg/g'was appeared for ultralow hydrogen analysis on the screen of the apparatuses which were based on the principle of impulse-heating fusion.The'zero peak'problem was investigated and discussed systematically.The experiments indicated that,if the graphite duplex crucible was replaced by single crucible,an obvious hydrogen peak could be observed under the same condition.It was the interference peak proved by the test of the 10-point analysis with the self-certification sample.The trial to solve the'zero peak'problem was failed by bath adding tests.But it was successful to solve the problem by other instrument based on induction-heating hot extraction.The induction-heating hot extraction instrument was applied to analyze hundreds of'zero peak'samples.The stable hydrogen peaks could be found in range of0.1-0.4μg/g.The instrument was calibrated with both Leco 502-457 and Alpha AR546 certified reference materials with certified value of(0.9±0.4)μg/g and(0.63±0.2)μg/g for hydrogen in steel.It was found that the linearity was good enough.The content of hydrogen in the self-certification steel sample was analyzed by induction-heating hot extraction method,and the results were basically consistent with the certified values of(0.5±0.2)μg/g.The standard deviation(SD,n=10)was 0.07μg/g.The comparison test for determination of ultralow hydrogen was designed for the rare earth steel samples with the rare earth free steel samples by the impulse-heating fusion and induction-heating hot extraction respectively.'0.0xμg/g'were shown on the screens of the two apparatuses based on impulse-heating fusion for the rare earth steel samples.The fine hydrogen peak with value about 0.4μg/g were appeared on the screen of the instrument based on induction-heating hot extraction to the same samples.The consistent results of hydrogen analysis were shown to the rare earth free steel samples by the three apparatuses/instruments.Therefore,it was considered that the addition of rare earths could cause negative interference with the analysis of hydrogen in steel.This interference value was very low and could be ignored for induction-heating hot extraction,while it was about 0.2-0.4μg/g for impulse-heating fusion.In conclusion,the impulse-heating fusion was not suitable for analysis of ultralow hydrogen in steel with mass fraction less than0.4μg/g,and should be cautiously applied for the analysis of ultralow hydrogen in steel with mass fraction ranging from 0.4μg/g to 0.9μg/g.On the other hand,the induction-heating hot extraction was entirely suitable for ultralow hydrogen analysis in steel which completed the analysis process with the sample keeping solid state.No more negative interference and no'zero peak'phenomenon have been observed from the instrument based on induction heating-extraction.