Hydrogen Content and Porosity Behavior of Hypereutectic Aluminum-silicon Alloy with Phosphorus

By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.

Effect of hydrogen content and stress state on room-temperature mechanical properties of Ti-6Al-4V alloy

This work aims to investigate the effects of hydrogen content(in the range of 0%-0.5%,mass fraction)and stress state (tension and compression)on the room-temperature mechanical properties of Ti-6Al-4V alloy through mechanical properties tests. The effects of hydrogen content on microstructure evolution of Ti-6Al-4V alloy is also examined by optical microscopy,X-ray diffractometry,transmission electron microscopy and scanning electron microscopy.The results show that hydrogen content and stress state have important effects on the room-temperature mechanical properties of Ti-6Al-4V alloy.Tensile strength and ultimate elongation decrease with increasing the hydrogen content,while compressive strength and ultimate reduction are improved after hydrogenation.The reason is that the intergranular deformation dominates at the state of tension.Hydrogen atoms in solid solution and hydrides at grain boundaries increase with increasing the hydrogen content and they can promote the initiation and propagation of cracks along grain boundaries.While the intragranular deformation dominates at the state of compression.The plastic beta phase and hydrides increase with increasing the hydrogen content and they improve the ultimate reduction and compressive strength.

Effect of hydrogen content on dielectric strength of the silicon nitride film deposited by ICP-CVD

The inductively coupled plasma chemical vapor deposition(ICP-CVD) deposited silicon nitride(SiN_(x)) thin film was evaluated for its application as the electrical insulating film for a capacitor device.In order to achieve highest possible dielectric strength of SiN_(x),the process parameters of ICP-CVD were carefully tuned to control hydrogen in SiN_(x) films by means of tuning N_(2)/SiH_(4) ratio and radio frequency(RF) power.Besides electrical measurements,the hydrogen content in the films was measured by dynamic secondary ion mass spectrometry(D-SIMS).Fourier transform infrared spectroscopy(FTIR) and micro Raman spectroscopy were used to characterize the SiN_(x) films by measuring Si-H and N-H bonds’ intensities.It was found that the more Si-H bonds lead to the higher dielectric strength.

Evolution of interfacial heat transfer,contact behavior and microstructure during sub-rapid solidification of molten steel with different hydrogen contents

Typical Q235 low-carbon steel samples with different hydrogen contents(0.0004,0.0008,and 0.0013 wt.%)were prepared by adjusting the environment humidity and moisture.The effects of hydrogen on interfacial heat transfer,contact behavior,and microstructure evolution were investigated using a novel droplet solidification technique.The results revealed that when the hydrogen content increases from 0.0004 to 0.0013 wt.%,the maximum heat flux between the molten steel and cooling substrate decreases from 8.01 to 6.19 MW/m^(2),and the total heat removed in the initial 2 s reduces from 10.30 to 8.27 MJ/m^(2).Moreover,the final contact angle between the molten steel and substrate increases from 103.741°to 113.697°,and the number of pores on the droplet bottom surface increases significantly from 21 to 210 with the increase in hydrogen.The surface roughness of the droplet bottom surface increases from 20.902 to 49.181 pm.In addition,the average grain size of the droplet increases from 14.778 to 33.548 pm with the increase in the hydrogen content.The interfacial contact condition becomes worse due to the escape of hydrogen from the steel matrix during the cooling process,which leads to the reduction in the interfacial heat transfer and the increase in the grain size.

XGBoost-based model for predicting hydrogen content in electroslag remelting

An Xtreme Gradient Boosting(XGBoost)-based endpoint hydrogen content prediction model was proposed for the electroslag remelting process,the data collected in the field were pre-processed,and the characteristic variables of the physical parameters related to the variation of hydrogen content in the electroslag remelting process were selected by machine learning analysis and metallurgical mechanism.The kernel ridge regression model,ridge regression model,XGBoost model,support vector regression model and gradient boosting regression model were developed and validated using the electroslag remelting data collected from the steel mills,and the model structure and parameters were adjusted several times.The prediction accuracy of hydrogen content was compared horizontally.The XGBoost model was validated for the test set with the following hit rates:70.59%,82.35% and 100% for the endpoint hits at the allowable hydrogen content error of ±0.05×10^(-6),±0.10×10^(-6) and ±0.50×10^(-6),respectively.

Improvement of the determination of hydrogen content in a multicomponent sample by D-T generator

If a D T generator is used as a neutron source to simultaneously measure the content of carbon, hydrogen and oxygen in a multicomponent sample by NIPGA （Neutron Induced Prompt Gamma-ray Analysis）, the 14 MeV neutron flux can be regarded as a constant value. The relationship between the production of the hydrogen characteristic gamma-rays and its content is nonlinear. In this paper, we use MCNP （Monte Carlo N-Particle Transport code） to simulate the relationship and analyze it. In practical measurement of the characteristic gamma-ray, it＇s impossible to get the net count. Therefore, we use the experiment to obtain the relationship between the hydrogen content and the total count of its characteristic gamma-rays. If we use the relationship combined with the simulation result to calculate the hydrogen content, the metrical precision can be much increased. The deviation of hydrogen content between NIPGA and chemical analysis is less than 0.25%, which meets the requirement of coal industry.

Infrared-transmission spectra and hydrogen content of hydrogenated amorphous silicon

In this paper, two kinds of methods of calculating the hydrogen content of a-Si:H thin film by means of the wagging mode and the stretching modes of infrared-transmission spectra , are investigated. The reason for the difference in these two calculation results is analyzed. If the contents of SiH2 and (SiH2)n are indicated in terms of a structure factor F=(I840+I880)/I2000, it is shown that the calculation results obtained from the two different methods are almost equal when the refractive index n is approximately 3.4 or the fitting thickness is between 0.71 and 0.89 mm in the case of a small F. It is shown that the ways of fabrication of thin film can influence silicon-hydrogen bonding configuration of a-Si:H film, and different ways of fabrication can lead to different contents of SiH2 and (SiH2)n. The uniformity of the thin film with a big F is bad. In this case, there is great difference between the thickness measured by the SurfCom408A surface profile apparatus and the thickness obtained by fitting the fringes; and the hydrogen contents of a-Si:H films obtained by means of the wagging mode and the stretching modes are different, too. But the fabrication of the MWECR CVD assisted by CAT CVD can effectively restrain the formation of SiH2 and (SiH2)n.

Influence of S Contents on the Hydrogen Blistering and Hydrogen Induced Cracking of A350LF2 Steel

In the present work, the effects of chemical compositions on the hydrogen blistering and hydrogen induced cracking of A350LF2 steel with different S contents were studied. Four types of A350LF2 steels were evaluated by immersing samples in H2S-saturated NACE solution. The hydrogen blistering, crack length rate(CLR), crack thickness rate(CTR) and crack sensitivity rate(CSR) were evaluated. The results show that there are many hydrogen blisters on the sample surface with S content of 0.021%, a few on the sample surface with S content of 0.019% and 0.012% and no one on the surface with S content of 0.002%. There were 12, 2 and 1 strips of cracks of longer than 0.3 mm on the evaluated cross sections with S content of 0.021%, 0.019% and 0.012%, respectively. There was no any crack in the sample with 0.002% S. The corrosion rate was also evaluated. The S content has no obvious influence on the corrosion rate.

中子成像技术在元素分析中的应用

中子成像作为一种快速、直观的无损检测技术,在核工业、航空航天、新能源、地质、考古、先进制造等多个领域得到广泛应用。中子成像利用中子不带电、穿透能力强、对轻元素敏感、可区分同位素和近邻元素等特性,非常适合开展含氢元素、近邻元素和同位素等材料的无损检测。通过概述中子成像技术的基本原理及特点,并结合中国先进研究堆(CARR)中子成像装置上的应用案例,重点综述了国内外中子成像技术在储氢材料、燃料电池、岩石、核燃料元件、古代文物等领域的典型应用。随着中子成像技术的不断发展和广泛应用,有望为我国更多领域研究提供更强有力的技术支撑。

用于MTO装置中的乙炔选择加氢催化剂研究

在MTO工艺装置生产乙烯的过程中,乙烯中常含有50~200μL/L左右的微量乙炔,现有的石油烃蒸汽裂解制乙烯装置中常用的碳二加氢催化剂或适用于微量乙炔选择加氢的乙烯精制催化剂并不是MTO工艺中乙炔选择加氢的最好选择。通过研究Pd含量变化对催化剂性能的影响,发现降低Pd含量能够提高催化剂的乙烯选择性,降低催化剂的乙炔合格温度,在保证乙炔加氢合格的情况下,通过控制较低的氢炔比还能获得更好的乙烯选择性。通过添加适当的助剂,控制助剂的用量也能够提高催化剂的乙烯选择性。和商业碳二加氢催化剂BC2相比,采用浸渍法制备的BC2-MTO催化剂活性组分Pd含量降低了50%以上,活性金属Pd的分散度提高了69%,能够在较低的反应温度和氢炔比条件下使用,具有更好的催化活性和乙烯选择性。

碘量法测定天然气中硫化氢标准适应性研究

GB/T 11060.1—2010中碘量法是天然气气质中硫化氢限制指标的测定方法之一,是GB 17820—2018《天然气》中硫化氢含量的仲裁方法。现行GB/T 11060.1—2010被广泛应用,在应用中发现存在的主要技术问题:(1)硫代硫酸钠标准滴定溶液配制和标定与GB/T 601—2016规定不完全相同;(2)对于产品天然气中硫化氢含量低,按该标准要求分析一个样品需要4~9 h,方法使用受到限制;(3)按标准规定的试样参考用量,吸收硫化氢的溶液中硫化锌沉淀多、颗粒大,滴定终点的颜色不明显,影响测量结果准确度。通过开展GB/T 11060.1—2010标准适应性研究,考察了标准溶液的配制和标定方法,以及不同的取样量、取样流速和吸收器等对测量结果的影响。研究结果表明:按照GB/T 601—2016配制的0.1 mol/L硫代硫酸钠标准滴定溶液并标定,由于滴定管校准、滴定速度和分析天平精度原因,标定结果不能完全符合GB/T 601—2016要求;硫化氢含量<28.7 mg/m^(3)试样参考用量降低为50 L,其重复性和再现性完全满足标准要求。根据实验结果、标准适用性和操作性等因素,提出了GB/T11060.1—2010的修订内容并修订发布GB/T 11060.1—2023。针对GB/T1106.1—2023新标准进行解读,以便使用者能更好地理解和掌握新标准,确保新标准的有效实施。

半再生重整装置催化剂硅中毒现象及分析

某炼油企业的半再生重整装置因重整催化剂活性下降而停工,更换了第一反应器和第二反应器的催化剂。对旧催化剂进行分析后发现,第一反应器催化剂二氧化硅质量分数高达20.40%,因此判断重整催化剂发生了硅中毒。在硅中毒期间:第一反应器的温降由初期的73.70℃下降到末期的20.12℃,重整反应后移到第二反应器;循环氢的氢气纯度上升到90%,纯氢产率下降到2.17%;稳定汽油RON(研究法辛烷值)下降到83.7。重整催化剂硅中毒较为罕见,其表现与氮中毒相似,容易误判为催化剂氮中毒。对硅进行溯源,确认是原油携带。分析认为:重整预加氢捕硅剂无法完全捕获所有硅,导致部分硅穿透预加氢系统;硅对预加氢催化剂的影响小于对重整催化剂的影响;硅中毒会导致催化剂的氯流失,需要加大注氯量。

感应加热中间包钢液氢含量控制

重轨钢氢含量是影响质量的关键因素之一。包钢感应加热中间包运行初期,重轨钢等钢种常常出现首炉氢超标的现象。基于此,本文详细分析了感应加热中间包钢液氢含量超标的主要原因,并对中间包材料、耐火材料和连铸工艺进行了优化改造。研究发现,中间包感应加热上线后,预制件数量较多,常规烘烤方式很难实现有效烘烤,这是导致包钢钢液氢含量偏高的主要原因;通过改进耐火材料材质,使用PVC管替代铁皮作为通道模具,利用下线铸坯和中间包的余热以及外置烧嘴对流钢通道预烘烤,烘烤时添加烘烤喷嘴,同时提前对预制件进行烘烤、浇注前氩气置换以及浇注工艺优化等方式,有效实现了浇次首炉氢含量低于2 ppm的目标。中包感应加热运行后生产了154个浇次不同钢种,氢含量全部满足目标要求,同时碳偏析指数平均降低了0.013,提高质量的同时获得了显著的经济效益。

高固含低黏度生物基氟碳树脂的合成及性能

将生物基原料氢化松香醇与三乙胺、对羟基苯甲醚、丙烯酰氯反应制备了可聚合的丙烯酸氢化松香醇酯,然后其与一系列丙烯酸及其衍生物通过共聚,制备了高固含低黏度生物基氟碳树脂。结合分子动力学模拟,分析了丙烯酸氢化松香醇酯降黏机理,探究了生物基氟碳树脂成膜后的涂膜性能。结果表明,随着丙烯酸氢化松香醇酯质量分数的增加,改性氟碳树脂运动黏度降低;当丙烯酸氢化松香醇酯质量分数为18.6%时,改性氟碳树脂固含量为78.56%,其运动黏度与石油树脂叔碳酸乙烯酯改性氟碳树脂相当,远低于不含大体积侧基的改性氟碳树脂;与叔碳酸乙烯酯相比,丙烯酸氢化松香醇酯的空间体积更大,侧基体积效应更明显,分子间作用力小,降黏效果好;丙烯酸氢化松香醇酯改性氟碳涂膜硬度、附着力高于叔碳酸乙烯酯改性氟碳涂膜,耐化学腐蚀性略低于叔碳酸乙烯酯改性氟碳涂膜。

35CrMo钢锭样坯裂纹成因分析

35CrMo液压室钢锭样坯在精加工时发现内孔壁有多条细微裂纹。为了查找裂纹成因,取样进行化学成分分析、低倍检验、金相检验和EDS分析。结果表明液压室钢锭样坯微裂纹系锻造时白点缺陷。分析了白点缺陷形成的主要因素为氢浓度、内应力(主要是组织应力)和夹杂物,在此基础上提出了白点缺陷的主要预防措施。

基于复杂因果关系模型的特征选择新方法及其在蜡油加氢工业装置上的应用

复杂因果关系模型的特征选择方法是当前人工智能领域的难点问题,开发新的特征选择方法对于因果关系模型的发展意义重大。以蜡油加氢工业装置为研究对象,针对模型涉及输入原料性质、操作参数等自变量特征和输出因变量特征精制蜡油硫含量之间复杂的因果关系,综合考虑输入变量两两之间的关系和输入变量与输出变量之间的关系筛选出合适的特征。首先,分别求出自变量特征之间和自变量与因变量之间的相关关系;其次,设计阈值和判别函数,将自变量、因变量结合起来,综合考虑两类变量之间的关系,最终将蜡油原料馏程中的初馏点筛选出来并剔除。相比传统的相关性特征选择方法,新筛选特征模型预测精制蜡油硫质量分数的平均绝对误差(MAE)减少62.97μg/g,平均相对误差(MRE)减少2.02百分点,决定系数R 2增加0.395,充分说明了新特征筛选方法对复杂因果关系模型的有效性。

适应炼油厂转型发展的沸-固复合床渣油加氢技术开发

为适应炼油厂转型发展需求,依托S-RHT固定床渣油加氢技术和STRONG沸腾床渣油加氢技术,中石化(大连)石油化工研究院有限公司开发了沸-固复合床渣油加氢技术。该技术采用单台沸腾床反应器承担原料预处理功能,大大改善了固定床进料性质,多台固定床反应器承担深度加氢精制功能,可明显提升加氢产品质量。中试试验结果表明:经过沸腾床反应器加工,劣质渣油原料金属(镍+钒)质量分数由123.1μg/g降低至38.9μg/g,后经过固定床反应器加工,金属质量分数降至8.8μg/g,加氢脱金属率达92.85%;该原料经过沸-固复合床加氢处理后氢质量分数增加1.58百分点,加氢脱硫率达到90.69%,加氢脱残炭率达到70.30%,加氢脱氮率达到53.73%,沥青质转化率达到82.87%。沸-固复合床渣油加氢技术实现了重质渣油的深度加氢转化,充分发挥了沸腾床和固定床加氢工艺各自的优势,可为后续加工装置提供优质进料。

12Cr1MoV钢过热器管开裂原因

某公司服役的12Cr1MoV钢过热器管在较短的时间内发生开裂现象,采用宏观观察、化学成分分析、硬度测试、氢气含量分析、扫描电镜分析、金相检验等方法分析其断裂原因。结果表明:由于管坯内部存在原始疏松缺陷,穿孔轧制后缺陷位于钢管内壁;在钢管服役过程中,锅炉气中超标氢分子扩散渗入管壁,在内部缺陷处富集,过热管弯管段存在较大的残余应力,使缺陷处发生氢致应力腐蚀开裂,最终导致过热器管开裂。

柴油加氢装置柴油产品硫、芳烃含量超标原因探讨

石油燃料的使用是导致大气污染的主要原因,而柴油中的硫、芳烃含量是影响污染的关键因素。柴油加氢装置生产运行至末期时,随着原料油性质、加工负荷、催化剂性能、生产方案、操作工况等条件的变化,装置中柴油产品硫、芳烃含量会出现超标现象,通过调整原料配比及性质、优化生产方案等方式,可实现对柴油加氢装置柴油产品硫、芳烃含量超标现象的有效控制,为同类生产装置提供借鉴。

基于包装油/盐的玉米醇溶蛋白膜中甘油迁移规律及变化机制

为探究包装高脂肪类食品和高盐粉类食品时玉米醇溶蛋白膜中甘油迁移规律及储藏中膜内部的变化机制,选择甘油添加量0.2 g/g、柠檬酸添加量0.2 g/g复合增塑制备的甘油/柠檬酸膜(CG膜)和甘油添加量0.15 g/g、聚乙二醇添加量0.2 g/g复合增塑制备的甘油/聚乙二醇膜(PG膜)包装油和盐并进行储藏。研究表明:在储藏过程中,CG膜中甘油迁移量高于PG膜;同一储藏温度,膜中甘油向盐中的迁移量高于向油中的迁移量;25℃储藏的膜中甘油向油中的迁移量高于5℃储藏,向盐中迁移时则相反;随储藏时间的延长,膜中水分含量逐渐降低;膜中氢键作用力逐渐减弱且与甘油迁移量呈负相关;膜中游离巯基含量逐渐降低,游离巯基含量受温度影响且与甘油迁移量呈负相关。CG膜更适合包装高脂肪类食品,PG膜更适合包装高盐粉状物。