惰气熔融-红外吸收法测定铬铝、钼铝中间合金粉中氧

铬铝(铝铬)、钼铝(铝钼)中间合金是重要的钛合金用新型合金剂,准确测定其中的氧含量有利于从源头上指导钛合金的质量控制。称取(100±50)mg样品采用锡囊包裹,设定分析功率为5.0～5.5kW,采用钢铁标准样品校准仪器(分析功率4.0kW),使用石墨套坩埚进行测定,建立了脉冲加热-惰气熔融-红外吸收法测定铬铝、钼铝中间合金粉中氧含量的方法。对样品量、分析功率进行了优化,并重点探讨了锡囊、镍箔、镍篮为助熔剂对氧量测定的影响。结果表明,助熔剂对氧含量的释放有较大的影响;部分程度上,镍箔、镍篮或会抑制或阻碍氧化铝中氧的释放,造成铬铝、钼铝中间合金中氧的释放率和测定结果存在显著偏低及不稳定的质量风险。在选定的实验条件下,方法检出限、定量限分别为0.004%、0.012%,定量范围为0.012%～0.58%。按实验方法分析铬铝、钼铝合金粉状样品,结果的相对标准偏差(RSD,n=6)不大于6%,极差显著小于参考YS/T 1075.7—2015《钒铝、钼铝中间合金化学分析方法第7部分:氧量的测定惰气熔融-红外法》计算的临界差(1.4倍重复性限)。采用加入氧化铝粉的方法合成加标样品,氧化铝中氧的回收率...

Determination of oxygen in chromium-aluminum and molybdenum-aluminum master alloy powder by inert gas fusion-infrared absorption method

Chromium-aluminum and molybdenum-aluminum master alloys are important novel alloying agents for titanium alloy. The accurate determination of oxygen content is advantageous to the quality control of titanium alloy from the origin. (100±50)mg of sample was weighed and wrapped with a tin capsule. The analytical power was set at 5.0-5.5kW. It was determined in graphite double-crucible using standard steel sample to calibrate the instrument (the analytical power was 4.0kW). The determination method of oxygen content in chromium-aluminum and molybdenum-aluminum master alloy powder by pulse heating-inert gas fusion-infrared absorption was established. The sample mass and analytical power were optimized. The effect of flux type including tin capsule, nickel foil and nickel basket on the determination of oxygen was discussed. The results showed that the release of oxygen was greatly affected by the flux. To some extent, the nickel foil or nickel basket as a flux maybe hinder the release of oxygen in aluminum oxide, resulting in the quality risk of significantly lower and instable release rate and measurement results of oxygen in chromium-aluminum and molybdenum-aluminum master alloys. Under the selected experimental conditions, the limit of detection and limit of quantification was 0.004% and 0.012%, respectively. The quantitation scope was 0.012%-0.58%. The chromium-aluminum and molybdenum-aluminum alloy powder samples were analyzed according to the experimental method. The relative standard deviations (RSD, n=6) were less than 6%. The range was much lower than the critical tolerance calculated by 1.4 times repeatability limit, which was defined in YS/T 1075.7-2015 . The spiked sample was synthesized by adding aluminum oxide (Al₂O₃) powder, and the recoveries of oxygen in aluminum oxide were between 90% and 109%. The proposed method was appliable for the determination of oxygen content in chromium-aluminum and molybdenum-aluminum master alloy powder. It was expected to be popularized in the analysis of new aluminum-based master alloys using chromium and molybdenum as alloying element, for titanium alloy, such as aluminum-molybdenum-chromium, aluminum-molybdenum-vanadium and vanadium-aluminum-tin-chromium.