钢中超低氢准确测定的影响因素探讨

Discussion on influence factors for accurate determination of ultralow hydrogen in steel

钢中氢质量分数低至0.Xμg/g时,测不准问题突显,实验对影响钢中超低氢测定的因素进行了探讨。采用稀土钢样品,应用感应热抽取法进行超声波清洗试验对比,结果表明简单的溶剂浸泡不能完全消除表面污染影响,超声波清洗程序必不可少。石墨坩埚与钢样的相互作用同样可以影响到超低氢分析的准确性,借助于加料空白可以观察到0.1μg/g的正干扰。通过实际样品和标样分析,可以观察到石墨单坩埚在高功率条件下有明显的干扰,套坩埚也可以存在干扰。新钢样中氢常规分析出现"零峰值"异常样,对现行脉冲熔融法和现行仪器提出了挑战,改用基于感应热抽取法的仪器可以解决问题。稀土元素挥发污染可以造成"零峰值"现象曾被试验证实,通过标样分析也观察到类似的异常现象。目前的热导检测器和红外检测器均适用于超低氢分析。综上所述:超声波清洗前处理、禁用石墨单坩埚和排除样品挥发干扰成为钢中超低氢准确测定的3个主要因素;感应热抽取法结合超声波清洗可以适合于各种钢样中超低氢分析的要求。

When the mass fraction of hydrogen in steel was low to 0.Xμg/g,the uncertainty problem for determination would be serious.The influence factors were discussed for determination of ultralow hydrogen in steel.The ultrasonic cleaning comparison test was conducted with rare earth steel sample by induction heat extraction method.The results showed that the simple immersion in solvent could not fully eliminate the influence of surface pollution,and the procedures of ultrasonic cleaning were necessary.The interaction between graphite crucible and steel sample could also influence on the accuracy of ultralow hydrogen analysis.With the help of filling blank,the positive interference of 0.1μg/g could be observed.The analysis results of actual samples and certified reference materials indicated that the graphite single crucible had obvious interference at high power,and the interference also existed in duplex crucible.During the routine analysis of hydrogen in new steel sample,the sample of abnormal＂zero peak value＂appeared,which challenged for the current pulse melting method and existing instruments.The use of instrument based on induction heat extraction method could solve this problem.The volatilization pollution of rare earth elements could cause＂zero peak value＂phenomenon,which had been proved by experiments.The similar abnormal phenomenon was also observed during the analysis of certified reference materials.At present,both thermal conductivity detector and infrared detector were suitable for the analysis of ultralow hydrogen.In conclusion,the pretreatment by ultrasonic cleaning,the nonuse of graphite single crucible and elimination of sample volatilization interference were three major factors for accurate determination of ultralow hydrogen in steel.The induction heat extraction combined with ultrasonic cleaning could meet the determination requirements of ultralow hydrogen in various steel samples.