Measuring Hydrogen Content in Molten Aluminium Alloys using the CHAPEL Technique

Abstract

A new method known as CHAPEL (Continuous Hydrogen Analysis by Pressure Evaluation in Liquids) for measuring hydrogen content in molten aluminium alloys has been developed and tested. The method relies on direct measurement of the hydrogen partial pressure in the melt. A number of interesting potential applications are indicated on the basis of laboratory and industrial experiences. The main advantage of the CHAPEL method, as compared to other techniques, is its ability to provide direct, continuous measurement of hydrogen in the melt, making it particularly suitable for process monitoring of aluminium melt quality. This paper systematically examines the influence of hydrogen content on porosity in aluminium-silicon cast alloys, taking solidification conditions and melt treatment into account. In this system, the greatest susceptibility to porosity is encountered with AlSi7Mg. An influence of the solidification rate on porosity, which varied with different hydrogen contents, was noted. The work describes a number of typical pore shapes and their distribution on the basis of metallographic studies.     

A comparative estimation of the forming load in the deep drawing process

The deep drawing process is one of the important sheet-metal forming processes. Using this operation, many parts are manufactured in various industries. In this paper, different methods of analysis such as analytical, numerical and experimental techniques are employed to estimate the required drawing force for a typical component. With this regard, the numerical simulations were conducted using the finite-element (FE) method. In these simulations, the effects of the element type on the forming load and the variation of the thickness strain were studied. Moreover, the influences of the friction coefficient on the load–displacement curve of the process and maximum drawing force were quantitatively investigated for both the analytical and FE methods. A die set including a blankholder was designed to carry out the experiments on a 600 kN Instron testing machine. Different analytical relationships suggested by different researchers were also used to calculate the maximum drawing force. The results obtained from these methods together with the numerical results were compared with the experimental findings. Based on this comparison, it was concluded that Siebel’s formula predicts more accurate results, compared with other analytical relationships. It was also found that this formula is more sensitive to the friction coefficient than the finite-element simulations. On the other hand, the shell elements are more suitable than four-node solid elements for the numerical analyses because the relevant FE predictions present much better agreement with the experimental results.     

在线式连续测氢仪在铝熔体表面吸氢特性研究中的应用

介绍了国内最新在线式连续测氢仪（ELH-IV）的测氢原理和结构。利用ELH-IV型快速测氢仪可在线连续测氢的特点,测量不同的熔体温度、保温时间以及熔体初始氢含最等工艺参数条件下铝熔体的表面吸氧情况,并分析了各参数对铝熔体表面吸氢特性的影响。     

铝及铝合金含氢量直接测定的研究与进展

阐述了铝铸件针孔产生的原因，对铝液直接测氢方法与装置进行了详细的评述。对铝液直接压力测氢方法进行了初步的研究，该方法测试简单，能在数分钟内测出铝液中氢的浓度。     

脉冲加热-红外法测定钽、铌中氢量

本文对应用TCH600氧氮氢分析仪脉冲加热-红外吸收法测定钽、铌中氢量的提取功率、分析积分时间、积分延迟时间、比较器水平、称样量等主要分析参数进行了较详细的试验和研究,结果表明,上述最佳参数分别为45 s,10 s,1%,0.05～0.1g。采用原冶金部行业标准铌粉以及LECO公司钛标中的氢量建立校正曲线。以此建立的分析方法对氢标准物质和样品进行准确度、精密度试验,标准测定值与认定值相吻合,相对标准偏差RSD在2.0%～4.2%之间(n=5)。     

镁熔体中含氢量检测方法的研究进展

当前对镁熔体中测氢研究较少,其原因主要是镁的蒸气压高,一方面造成测氢器皿的污染,另一方面挥发出来的镁对析出的氢气再次吸收,使测量的数据精确度低,再现性变差.综述了镁熔体中含氢量的检测方法,并展望了镁熔体中测氢技术发展的方向.     

A new dynamic method for measuring hydrogen partial pressure in molten aluminum alloy

Hydrogen partial pressure is an important parameter to calculate hydrogen concentration levels in molten aluminum alloy. A new dynamic method for measuring hydrogen partial pressure in molten aluminum alloy is studied. Dynamic and rapid measurement is realized through changing the volume of the vacuum chamber and calculating the pressure difference ΔP between the theoretical and measured pressures in the vacuum chamber. Positive ΔP indicates hydrogen transmits from melt to vacuum chamber and negative ΔP means the reverse. When ΔP is equal to zero, hydrogen transmitted from both sides reached a state of dynamical equilibrium and the pressure in the vacuum chamber is equal to the hydrogen partial pressure in the molten aluminum alloy. Compared with other existing measuring methods, the new method can significantly shorten the testing time and reduce measuring cost.     

Prediction of Tensile Property of Hydrogenated Ti600 Titanium Alloy Using Artificial Neural Network

An artificial neural network (ANN) model has been developed to analyze and predict the correlation between tensile property and hydrogenation temperature and hydrogen content of hydrogenated Ti600 titanium alloy. The input parameters of the neural network model are hydrogenation temperature and hydrogen content. The output is ultimate tensile strength. The accuracy of ANN model was tested by the testing data samples. The prediction capability of ANN model was compared with the multiple linear regression approach and response surface method. The combined influence of inputs on the tensile property is also simulated using ANN model. It is found that excellent performance of the ANN model was achieved, and the results showed good agreement with experimental data. Moreover, the developed ANN model can be used as a tool to control the tensile property of titanium alloys.     

熔化条件和除气工艺对镁熔体含氢量的影响

利用自行开发的镁合金定量测氢仪研究了熔化条件和除气工艺对镁熔体含氢量的影响。研究结果表明,镁熔体中的含氢量随温度的升高而增大;气体保护下熔炼比熔剂保护的效果好,含氢量较低;随保温时间的延长,气体保护下的镁熔体含氢量几乎没变化,而熔剂保护下的含氢量成小幅上升趋势;采用Ar气除气工艺的效果比C2Cl6除气更有效,镁熔体含氢量更低。     

铝镁合金熔体中氢含量的测定

通过用HYSCANⅡ测量不同过热度和镁含量的铝镁合金熔体中的氢含量，研究了铝镁合金熔体过热度、镁元素和氢含量的关系。试验结果表明，铝镁合金熔体中的氢含量随温度的升高而增加；氢在铝镁合金熔体中的存在形态不同，其可逆性也不同；通过热速处理可大大减少过热铝镁合金熔体中的氢含量；铝镁合金液吸氢的程度主要取决于镁对铝液表面氧化膜性质的改变。     

Al-Si-Mg系铝合金熔体吸氢热力学研究

通过建立铝合金熔体吸氢的热力学过程模型,分析了影响Al-Si-Mg系铝合金熔体吸氢的热力学因素。结果表明,降低空气湿度、熔炼温度、压力有利于降低铝液吸氢速率;Si、Mg含量与空气/铝液界面处的氢含量成线性关系,提高Si含量、降低Mg含量有利于降低空气/铝液界面处的氢含量,从而降低铝液的吸氢速率。     

一种用于显示中高强度钢晶粒的方法

中高强度钢随着碳含量的逐渐增加,组织愈发细小,通过直接腐蚀等传统方法得到的晶界往往比较模糊。为了能够清晰地显示中高强度钢的晶粒度,利用其具有氢脆敏感性以及氢脆易于产生沿晶断裂形貌的特点,提出了一种晶粒度检测方法。通过对 55SiCr弹簧钢和 440冷墩钢分别使用直接腐蚀、电子背散射法（EBSD）与氢致开裂断口法显示晶界,对比可以发现在中高强度钢的晶粒度检测中,氢致开裂断口法显示的晶界更为清晰,评定的结果更加准确。     

Effect of hydrogen content,melt cleanliness and solidification conditions on tensile properties of A356 alloy

Abstract

In this study, the influence of hydrogen content, melt cleanliness and solidification conditions on the porosity distribution and mechanical properties have been investigated in a laboratory scale step mould casting with an A356 alloy. Three hydrogen levels, namely 0·10, 0·20 and 0·40 mL/100 g, were reached by treatment of the melt by Ar degassing, Ar–10H₂ and Ar water vapour mixture respectively. The hydrogen content of the melt was continuously measured. For each hydrogen level, two castings were produced, namely with and without filter. Porosity was increased with increasing hydrogen content but there was no significant effect of filtration. Moreover, similar tensile properties were achieved with different hydrogen levels and different porosity levels.     

Catalytic Properties of Gold Nanoparticles Prepared in Reverse Micelles

Adsorption and catalytic properties of gold nanoparticles of various sizes prepared by two methods of reduction in reverse micellar solutions were studied. Gold nanoparticles are capable of adsorbing molecular hydrogen and exhibiting catalytic activity in reactions of ortho—para conversion of protium and deuterium—hydrogen exchange. The size dependence of the catalytic activity of gold nanoparticles in reaction of H₂—D₂ exchange regardless of the method of preparation was determined.     

基于全矢最小二乘支持向量机的设备状态趋势预测

在支持向量机(SVM)基础上拓展出的最小二乘支持向量机(LS-SVM)非线性泛化能力更好,具有较高的拟合和预测精度,目前被广泛应用于设备状态趋势预测中。为进一步提高其预测精度,结合基于同源信息融合的全矢谱技术提出一种新的趋势预测方法——全矢LS-SVM。该方法采用全矢谱技术融合双通道信息,相比传统单通道信号提取方法,保障LS-SVM预测数据特征提取的完整性,提高预测精度。将该方法应用于某电厂1号汽轮机振动数据的预测,实验结果表明,全矢LS-SVM方法具有较高的预测精度。     

铝、镁合金中氢含量检测方法研究进展

由于铝合金及镁合金熔体熔炼过程中的大量吸氢而会严重影响到合金的组织和性能,因此,测定铝合金以及镁合金熔体中的氢就是必须解决的问题.详细总结了铝合金、镁合金中氢含量的检测手段,包括取样法、直接测定法和其他方法,并比较了每种方法的优缺点.提出了铝合金、镁合金中氢检测的发展方向:镁合金的测氢将是未来的热点之一.开发一种炉前能够快速、准确、简单的镁合金测氢仪是镁合金测氢的未来发展趋势,而铝液中直接测氢代替取样法也是未来发展的趋势之一.     

氢还原重量法测定三氯化钌中Ru含量

系统地研究了通氢还原重量法测定三氯化钌中钌含量的分析方法.确定了分析过程中的最佳分析条件,并与其它方法对同一样品的分析结果作比较.结果表明,本法具有准确度高、回收率好、操作简便、易于掌握等优点,加标回收率≥98.92%.此方法已用于实际样品的分析,结果令人满意.     

The effects of purge gases on the hydrogen content and mechanical properties of spray-degassed Al

Spray degassing was used to remove hydrogen dissolved in aluminum melt. In order to investigate the effects of different purge gases on aluminum melt during spray degassing, different kinds of purge gases were used in experiments. The results show that, as a purge gas in the process of spray degassing, nitrogen leads in increasing the hydrogen content and inclusion content of the aluminum melt. The mechanical properties of the specimens are very poor.     

低钛铝合金的电解生产与晶粒细化

在电解低钛铝合金的工业化生产试验中，研究和对比了电解加钛和熔配加钛低钛铝合金的晶粒细化效果及其衰退行为。结果发现：电解质中添加少量TiO2对电解槽铝产量和电流效率影响较小，二者分别维持在1200kg和92％左右，钛的吸收率在95％以上所生产的合金钛含量稳定，晶粒细化效果明显，晶粒尺寸随钛含量的变化趋势与熔配加钛合金相同；钛含量在0．1％～0．2％范围内时，电解加Ti合金晶粒细化效果的抗退化能力比熔配加Ti合金的强。     

Variation of hydrogen level in magnesium alloy melt

M agnesium alloy is one of the lightest metals used in industry. It offers numerous merits in physical, mechanical and casting properties: high specific strength and stiffness, good castability suitable for high pressure die casting, low density, high damping capacity, good thermal and electrical conductivity etc. [1] However, microporosity in the castings reduces mechanical properties [2-4] such as ultimate strength, yield strength, ductility and fatigue resistance. There are mainly two viewp…