管线钢氢脆研究现状及进展

从管线钢的氢脆现象、氢脆影响因素以及氢脆机理和研究方法等方面综述了管线钢氢脆的研究现状和进展。介绍其他相关领域研究氢影响材料性能的先进方法及手段,期望管线钢领域借鉴相应的研究方法以明确氢对管线钢性能的影响规律及作用机制,为提出有效的氢脆问题解决方案提供依据,从而保障油气输送管道的安全运行。     

掺氢天然气环境下管道钢氢脆行为研究进展

为推动我国掺氢天然气管道的发展,综述了目前含氢气环境下管道钢氢脆的研究成果,总结了温度、压力、掺氢比等运行条件对钢材氢脆的影响,分析了钢材强度、微观组织、氢陷阱等材料性质与管道钢氢脆行为之间的联系,归纳了预防和抑制管道钢氢脆行为的方法。笔者认为,当前亟待解决的科学技术问题包括进一步探究掺氢天然气管道环境下不同运行条件对管道钢氢脆行为的影响规律;确定掺氢天然气管道的安全运行温度、压力、掺氢比等关键参数;建立不同服役条件下掺氢天然气管道输送的安全评价方法,完善掺氢天然气管道与现役管道相容性评价体系;形成掺氢天然气管道的设计规范和相关标准;开展气体抑制剂和阻氢涂层等抗氢脆方法的评价。     

氢在钢铁表面吸附以及扩散的研究现状

氢进入钢铁内部是其发生氢脆的前提,而氢在管线钢表面经历物理吸附、解离、化学吸附、扩散一系列过程才能进入管线钢内部,其中氢原子的化学吸附以及氢扩散是关键步骤。综述了氢在钢铁表面吸附、扩散的研究方法、成果,展望了氢吸附以及氢扩散的研究方向。目前研究氢吸附的主流方法是第一性原理计算。在氢扩散研究方面,试验研究能够分析钢铁组织、相、宏观尺度因素变化对氢扩散的影响;有限元、分子力学、第一性原理多种尺度模拟计算可以分析微区结构变化对扩散的影响。氢在表面的吸附以及表层原子的扩散对氢脆有重要影响,但氢原子在钢铁表面的吸附以及表层扩散主要集中在无缺陷的αFe表面。氢与缺陷的相互作用研究主要集中在体相内部,钢铁表面状态的变化对氢吸附以及表层扩散的影响相关报道较少。需进一步开展在含缺陷钢铁表面的氢吸附研究,阐释表面应力、位错、晶界、相界、合金元素等因素对氢吸附、表层区域氢扩散的影响机理。     

输氢管道钢管研究进展

简述了国内外纯氢及掺氢输送管道的建设现状、输氢管道技术规范的发展现状以及国内外氢气系统的储存、输送、管道设计、临氢材料的试验和评价等。指出随着材料的强度、易于形成偏析的化学元素含量、夹杂物的尺寸和数量、氢气的压力和纯度等的提高，材料的氢脆敏感度增大。焊接钢管的焊接接头等薄弱部位会提高管道的氢脆敏感性；输氢管道的选材应关注钢材纯净化，化学成分设计，非金属夹杂物形态、组织偏析和带状组织控制，涂层方式等。     

管线钢氢渗透行为的研究进展

天然气管道掺氢输送是现阶段氢能输送最为经济有效的方式之一,但必须重视管材与氢的相容性问题。天然气中掺入氢气后,氢通过吸附、扩散等过程进入金属管材内部,部分被氢陷阱捕获,部分在晶格间扩散。进入金属管材内部的氢是影响管线钢服役性能的关键,因此,研究管线钢氢渗透行为具有十分重要的意义。本文从管线钢的氢渗透研究方法以及影响因素等方面综述了管线钢氢渗透行为的研究进展。     

不同电化学充氢状态下X70、X80管线钢的断裂特性

X70、X80高级管线钢主要用于油气田管道,如果长期在常温高压（压力最高可达25 MPa）的氢环境中使用,极有可能会出现氢脆现象,进而引发脆性破坏事故。本文通过对X70、X80两种管线钢的静态和动态电化学充氢试验,对两种管线钢在不同充氢状态下的氢含量等进行了分析,并详细讨论了其断口形貌。     

不同电化学充氢状态下X70和X80管线钢的断裂特性

X70、X80高级管线钢主要用于油气田管道,如果长期在常温高压(压力最高可达25 MPa)的氢环境中使用,极有可能会出现氢脆现象,进而引发脆性破坏事故。本文通过对X70、X80两种管线钢的静态和动态电化学充氢试验,对两种管线钢在不同充氢状态下的氢含量等进行了分析,并详细讨论了其断口形貌。     

输氢海底管道选材探讨

针对国内首条输氢海底管道进行选材探讨,基于对常见的氢致失效形式及机理的分析,参考国内外输氢管道相关的标准规范,并考虑海底管道安装的特殊性,推荐输氢海底管道选用API SPEC 5L X42和X52无缝钢管(PSL2等级优先),采用淬火+回火的热处理工艺。同时,对一些氢脆影响因素进行控制,如合金元素含量、碳当量、管材硬度和非金属夹杂物含量等。可以采用慢应变速率试验、断裂韧性试验、裂纹扩展速率试验、疲劳寿命试验和圆盘压力试验等,对管道材料进行力学性能评价,判断材料在氢环境中的氢脆敏感性,为实际工程应用提供支持。     

我国长输天然气用管线钢的发展现状与趋势

随着国内天然气管道的大规模建设,我国长输天然气用管线钢及钢管的生产制造技术也迅速发展并达到世界先进水平。天然气管道仍将朝着高强度、大口径、高压力、大壁厚、低温服役等方向发展,对高钢级管线钢特别是抗大变形管线钢、低温环境用管线钢等提出了更高的要求。本文着重从管线钢的合金成分体系、组织类型、轧制工艺的演变及其与管线钢的性能间的关系等角度,对高钢级管线钢、抗大变形管线钢及低温环境用管线钢的发展现状进行了综述,并结合目前应用中存在的一些问题对我国长输天然气管道用钢的发展趋势进行了探讨。     

X60、X70管线钢及其焊接接头氢脆敏感性的对比研究

目的 开展电解渗氢管线钢及其焊接接头显微组织和力学性能研究,为掺氢天然气管线服役安全可靠性评估提供支持。方法 X60、X70管线钢及其焊接接头试样在100 mA/cm2下进行24 h电解渗氢后,开展有、无渗氢情况下相关试样的显微组织结构、氢热脱附、拉伸力学性能与断口形貌测试分析,揭示渗氢对X60、X70 2种管线钢及其焊接接头氢脆敏感性的影响规律。结果 X60及X70管线钢以细小多边形铁素体为主,其焊缝和热影响区以粗大的粒状或板条贝氏体为主。相对于X70管线钢,其焊接接头具有更高的氢渗透性和稳定性。渗氢导致X60、X70管线钢及其焊接接头试样的强度与塑性降低,渗氢X70焊接接头力学性能衰减最为明显,拉伸断口呈准解理断裂特征。结论 X70管线钢的氢脆敏感性高于X60管线钢,管线钢焊接接头的氢脆敏感性高于母材。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.