Abstract：The determination method and related issues of ultralow hydrogen (w(H)<1.0 μg/g) in metal materials such as steel, copper, aluminum and superalloy were discussed. Ultralow hydrogen in steel had been neglected for a long time, until the emergence and resolution of "zero peak" problem, which opened a channel for the accurate determination of "ultralow hydrogen in steel". Three instruments based on two types of heating and gas extraction principles were used to measure four standard samples of ultralow hydrogen in steel with known contents. The results showed that the analysis data of four groups of hydrogen analyzer based on the principle of high-frequency and heat extraction were consistent with the certified values of the standard sample, and the success rate was 100%. However, the success rate of analytical results based on impulse-fusion method was only 50%, and one set of data was seriously out of tolerance. When the instrument based on impulse-fusion method was employed, the success rate of the actual sample of ultralow hydrogen in steel was difficult to reach 100%. Taking the "common sample" as an example: the 10-point measurement result of ultralow hydrogen in steel was (0.16±0.19) μg/g; the standard deviation value was greater than the average value, and the analysis failed. On the contrary, the 10-point detection result based on high-frequency and heat extraction method was (0.13±0.02) μg/g, and the data were reliable and credible; the measurement result based on tubular furnace and heat extraction method was (0.13±0.04) μg/g, which was also reliable and credible. The analysis of ultralow hydrogen in copper was easily interfered by the surface oxide layer, so that the released hydrogen was absorbed by the reaction and could not reach the detector completely. The determination of ultralow hydrogen in copper samples with clean surface could reduce the interference of oxide layer to the minimum. The analysis of ultralow hydrogen in aluminum was relatively mature and a national standard method had been formed. The "residual hydrogen" in aluminum samples could be detected according to the national standard method. In other words, the hydrogen peak by the second dropping could been seen with the same order of magnitude as that of the first sample dropping, and the problem of hydrogen peak of the second dropping sample had become a key problem troubling the implementation of the national standard. The proposed work focused on the solving of the "second dropping sample problem". The experiment showed that this problem was caused by the graphite crucible. If the quartz crucible was used for the second dropping sample, the measurement results totally turned to zero (0.0 μg/g). The secondary hydrogen peak was the interference peak caused by graphite crucible rather than the "residual hydrogen" peak, which indicated that this problem did not interfere with the implementation of national standard. The main interference during the analysis of ultralow hydrogen in superalloys was also from the graphite crucible. The phenomenon of "non-ultralow hydrogen" was still encountered after the removal of crucible factors. The transverse and longitudinal dissection, sampling and analysis of superalloy were conducted to observe the distribution of hydrogen. The results showed that the phenomenon of "non-ultralow hydrogen" was caused by the sampling site, and the center of transverse section had "non-ultralow hydrogen" sites. The longitudinal distribution was relative uniform and outliers were not observed. The analysis of ultralow hydrogen samples should avoid the abnormal sites. The longitudinal sampling was more reasonable compared to the transverse sampling.
林文泉,何永年.高频加热——热导法测定钢铁、铜、铌、钽、钛中的氢[J].钢铁研究学报,1995,7(2):70-75.LIN Wenquan,HE Yongnian.Determination of hydrogen in steel, copper, niobium, tantalum and titanium by hight frequency induction-thermal conductivity method[J].Journal of Iron and Steel Research,1995,7(2):70-75.
[2]
陈文绣,陈文,李素娟.氮载气熔融法测定铝锂合金中氢[J].冶金分析,1994,14(2):6-8.CHEN Wenxiu,CHEN Wen,LI Sujuan.Determination of hydrogen in Al-Li alloy by nitrogen carrier gas fusion method[J].Metallurgical Analysis,1994,14(2):6-8.
[3]
朱跃进,李素娟.惰气熔融法测定镁中氧、氢、氮[J].冶金分析,2011,31(12):58-61.ZHU Yuejin,LI Sujuan.Determination of oxygen, hydrogen and nitrogen in magnesium by inert gas fusion method[J].Metallurgical Analysis,2011,31(12):58-61.
[4]
谢君,朱瑛才,仉凤江,等.坩埚对高温合金中氧氮及氢分析结果的影响[J].冶金分析,2018,38(10):7-15.XIE Jun,ZHU Yingcai,ZHANG Fengjiang,et al.Influence of crucible on analysis results of oxygen, nitrogen and hydrogen in superalloy[J].Metallurgical Analysis,2018,38(10):7-15.
朱跃进,李素娟,邓羽,等.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[J].冶金分析,2017,37(6):1-8.ZHU Yuejin,LI Sujuan,DENG Yu,et al.Discussion on “zero peak” problem of ultralow hydrogen analysis in steel by impulse-heating fusion and induction-heating hot extraction[J].Metallurgical Analysis,2017,37(6):1-8.
朱跃进,李素娟,邓羽,等.钢中超低氢准确测定的影响因素探讨[J].冶金分析,2018,38(6):12-18.ZHU Yuejin,LI Sujuan,DENG Yu,et al.Discussion on influence factors for accurate determination of ultralow hydrogen in steel[J].Metallurgical Analysis,2018,38(6):12-18.
[9]
朱跃进,李素娟,高鹏.脉冲热导法测定铝中氢的探讨[J].冶金分析,2016,36(12):18-25.ZHU Yuejin,LI Sujuan,GAO Peng.Discussion on determination of hydrogen in aluminium by impulse heating thermal conductivity[J].Metallurgical Analysis,2016,36(12):18-25.
谢君,严志,侯桂臣,等.氧氮氢碳硫在镍基高温合金锭中分布的研究[J].冶金分析,2020,40(11):17-25.XIE Jun,YAN Zhi,HOU Guichen,et al.Study on distribution of oxygen, nitrogen, hydrogen, carbon and sulfur in nickel-based high temperature alloy ingot[J].Metallurgical Analysis,2020,40(11):17-25.
