水银法测定焊缝扩散氢的影响因素

采用水银法研究了环境湿度、烘干温度、保护气体露点等测试条件对焊缝扩散氢含量的影响,分析了我国碳钢及低合金风焊条中的扩散氢含量,并且与国外焊条的扩散含量进行了对经     

焊缝金属中扩散氢的形成及控制研究进展

 随着焊接技术的广泛应用,焊接接头冷裂纹的形成也备受关注。焊缝中的扩散氢是导致焊缝区产生氢致裂纹的重要原因之一。详细综述了近年来焊缝金属中扩散氢的来源、产生和扩散氢质量分数测定方法的研究进展,总结了影响扩散氢质量分数的有关因素。着重分析了氢在焊接接头的动态扩散行为,对扩散氢的危害和预防措施进行总结,并对相关研究存在的问题和进一步的研究方向进行概括。     

MnS夹杂对钢中氢扩散行为的影响

通过实验和有限元计算研究了MnS夹杂对钢中氢扩散行为的影响.结果表明:当MnS夹杂长度取向与氢渗透方向平行时,氢在钢中的表观扩散系数随MnS含量的增加而增加;当MnS夹杂长度取向与氢渗透方向垂直时,氢在钢中的表观扩散系数随MnS含量的增加而降低.对于具有扩散通道效应和陷阱效应的第二相,它对氢扩散的影响取决于扩散通道效应和陷阱效应的强弱以及第二相的形状、数量和取向.     

利用HTDS对钢材料中氢扩散行为的分析研究

介绍了利用升温测氢装置(HTDS)进行的钢材料中扩散氢及非扩散氢定量区分与检测的方法,绘制出不同温度下氢扩散速率曲线图,找出最佳扩散温度区间。通过对管线钢服役中失效样品中扩散氢和不易扩散氢的测定,为失效分析提供有力判据。     

钛合金钎缝中元素的扩散行为研究

采用钛基钎料钎焊TC4板材,在钎焊接头组织和力学性能分析的基础上,确定合理的工艺规范,并从理论上对TC4板材钎缝中元素扩散行为进行了分析,总结出了较为普遍的规律。     

硫化氢环境下氢扩散的影响因素

采用典型的电化学渗氢装置,对材料的化学成分、焊接和环境中CO₂和NH₄⁺的质量浓度、溶液的pH值对硫化氢应力腐蚀开裂中氢扩散行为的影响进行了研究.结果表明:金属中夹杂物数量、焊缝金属中空位和焊接缺陷使得氢扩散系数增加;在硫化氢环境中,氢扩散稳态电流随pH值的增加而降低,随着NH₄⁺的质量浓度的增加而增加,且增加幅度随着pH值的增加而加大;CO₂的质量浓度对氢稳态扩散电流的影响是随着pH值的变化而起着不同的作用,在低pH值条件下氢稳态扩散电流随着CO₂的质量浓度增加而增加,在较高的pH值中氢稳态扩散电流随着CO₂的质量浓度增加而减小.     

308L和347L焊缝金属的氢致滞后断裂行为

奥氏体不锈钢３０８Ｌ和３４７Ｌ的焊缝金属能发生氢致滞后断裂,而且比３０４Ｌ母材更敏感。用单边缺口试样动态充氢法测出的氢致滞后断裂门槛应力强度因子ＫＩＨ随可扩散氢浓度ＣＯ的对数而线性下降。３种材料氢致滞后断口的形貌与ＫＩ以及ＣＯ有关,当ＫＩ较高或ＣＯ较小时是韧窝断口;当ＫＩ较低或ＣＯ较高时是脆性断口。     

高强海工钢EH36中氢扩散行为研究

通过显微组织表征明确了高强海工钢EH36厚板心部和表面组织的差异,进而通过氢渗透测试、内耗、氢脆敏感性指数测定等实验研究了EH36厚板心部和表面位置的氢扩散行为。结果表明,EH36厚板的表面和心部组织分别为贝氏体组织和铁素体+珠光体组织。心部组织的氢陷阱数量较少,组织溶氢能力较弱,氢扩散系数较高,氢扩散穿透时间较短。钢中间隙氢原子的扩散导致了充氢后实验钢的内耗峰在低温区出现了H-Snoek峰,同时氢的存在使得SKK峰发生偏移。相比于心部位置,由于实验钢表面的组织中所含界面较多,导致其内耗谱在高温区出现较弱的晶界峰。实验钢心部粗大的铁素体+珠光体组织导致其氢脆敏感性指数较高,抗氢脆失效能力较弱。此外,钢中氢原子的大量存在会显著弱化柯氏气团对可动位错的钉扎作用,降低实验钢的屈服点延伸率。     

钢板中氢扩散的数值模拟

为了加强钢板生产过程中氢的控制,建立了钢板内部氢扩散的数学模型,分析了钢板芯部的氢质量分数与扩散系数、钢板的厚度、氢的初始质量分数和时间之间的关系。随着钢板的厚度增加,氢的扩散效果大幅度降低;随着钢板缓冷开始温度的降低,同一厚度钢板芯部氢的扩散效果也越来越差。采用高温堆垛缓冷或采用保温坑缓冷等工艺可实现高温扩氢,从而避免轧后钢板的氢致缺陷。     

Stress Oriented Hydrogen Induced Cracking of Linepipe Steel

The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed.     

A Carbon-Stabilized Austenitic Steel with Lower Hydrogen Embrittlement Susceptibility

High-strength steels are susceptible to H-induced failure, which is typically caused by the presence of diffusible H in the microstructure. The diffusivity of H in austenitic steels with face-centered cubic (fcc) crystal structure is slow. The austenitic steels are hence preferred for applications in the hydrogen-containing atmospheres. However, the fcc structure of austenitic steels is often stabilized by the addition of Ni, Mn, or N, which are relatively expensive alloying elements to use. Austenite can kinetically also be stabilized using C. Herein, an approach is applied to a commercial cold work tool steel, where C is used to fully stabilize the fcc phase. This results in a microstructure consisting of only austenite and M₇C₃ carbide. An exposure to H by cathodic hydrogen charging exhibits no significant influence on the strength and ductility of the C-stabilized austenitic steel. While this material is only a prototype based on an existing alloy of different purposes, it shows the potential for low-cost H-resistant steels based on C-stabilized austenite.     

Determination of Hydrogen in Steel by Thermal Desorption Mass Spectrometry

Hydrogen embrittlement has been observed since high‐strength steels have been produced in the nineteen thirties 1 . Several different analytical methods have been developed to quantify the total and diffusible hydrogen in steel, but many aspects of hydrogen determination are still to be explored. Purely quantitative determination of hydrogen is not sufficient to fully characterize the steel regarding its resistance against embrittlement. Thermal Desorption Mass Spectrometry (TDMS) allows the investigation of hydrogen absorption and desorption mechanisms to characterize hydrogen traps in different kinds of steel microstructures. This provides valuable information for the development of new materials with a higher resistance against hydrogen embrittlement. Additionally, TDMS allows the quantitative determination of very small concentrations of hydrogen (<0.1 µg/g). Such low detection limits cannot be reached with other methods. Due to time‐consuming analysis and a rather complex construction, TDMS is usually not applied for hydrogen determination in German steel mills. The present work describes the development of a thermal desorption spectrometer at ThyssenKrupp Steel Europe AG by adapting a compact quadrupole mass spectrometer to a commercially available hot solid extraction analyzer, which has proven to be a simple and efficient solution for the determination of diffusible hydrogen in steel.     

循环伏安法测定纳米晶贮氢合金中氢扩散系数

用双辊快淬法制备了纳米晶稀土贮氢合金,XRD图谱表征为结晶较好的CaCu5六方结构,Scherrer公式计算晶粒大小约为40nm。利用循环伏安法测定了纳米晶稀土贮氢合金电极中的氢扩散系数(DH=1.67×10-7cm2/s),由于纳米晶粒具有较高的结晶度和细小的晶粒尺寸,高密度晶界为氢在合金内部的扩散提供快速通道,提高了贮氢合金的吸放氢效率,从而提高了氢的扩散性能,使电极中氢的扩散系数增大。     

Relationship between Hydrogen Diffusion and Blistering Nucleation and Growth

The formation condition of hydrogen blister in 18 Ni maraging steel without any inner or external stress was investigated.The results show that the critical diffusible hydrogen concentration of a blister forming is about 1.4×10~(-5),which is corresponding to the current density of 30mA/cm~2 during cathodic charging in a sodium hydroxide solution.For a 0.1cm thick sample,no matter the current density is equal to or much larger than the critical value,it spends at least about 132 hto form a hydrogen blister when hydrogen charging in single direction.It is approximately equal to the time for hydrogen atom to diffuse throughout the sample,which exactly depends on the hydrogen diffusion coefficient and the penetration depth.The very first clear suggestion was reported that the incubation period for hydrogen blister nucleation was necessary.According to the Fick′s laws,calculations show that the normalized hydrogen concentration in the escaping surface almost reaches 0.96 times of the charging surface,which means that the diffusion almost reaches a dynamic balance.A model was illustrated to describe the competitive relationship between hydrogen diffusion and blister formation.     

Weld Quality Assessment and Actions

Since 1989, Nordic industries, organizations and universities have co‐operated in numerous projects related to the design and fabrication of welded structures. In a current ongoing project, QFAB, over 20 participants are working together to improve the design, fabrication and cost effectiveness of complex welded structures. This paper describes the background to this project and will also discuss the process of quality assessment of welded construction machinery. The main part of the supporting framework on vehicles consists of welded steel structures. These welds contain defects and imperfections from the weld process itself and when severe load conditions are present, a finite life is at hand. The competition among manufacturers towards higher productivity and lower fuel consumption drives the engineers to design lighter structures preferably in high strength material. Such a design requires a higher weld quality and calls special attention to design and manufacturing of welds. A major issue is thus to form a scientific and consistent base which can be used when analysis and design is integrated with production and quality inspection of components. The goal is to build world class vehicles for operation without failures in service during the economic life.     

Study on Diffusion of Hydrogen in AB5 Non－Stoichiometric Hydrogen Absorbing Alloys

The diffusion coefficient of hydrogen atoms in the studied alloys was electrochemically measured by chronoamperometry when the metallic hydride microelectrodes were completely discharged. It is found that the diffusion coefficient of hydrogen atoms decreases when cobalt is substituted for a minority of nickel. On the contrary, the diffusion eoefficient increases with the partial substitution of manganese or aluminum for nickel, which is related to the lattice constant and cell volumes of hydrogen absorbing alloys. The lattice constant c is obviously affected by the substitute elements greatly. The result shows that the expansion of cell volume resulted from the increase of value c causes the increase of diffusion coefficient which is especially obvious when the lattice constant is relatively low. However, this relationship is not clear if the lattice constant increases to some extent. It is suggested that this phenomenon is related to the interaction of hydrogen atoms with metallic atoms.     

Study on Diffusion of Hydrogen in AB_5 Non-Stoichiometric Hydrogen Absorbing Alloys

AB5hydrogenabsorbingalloyshavebeenexten sivelyusedontheproductionofnickelmetallichy dridebatteriesbecauseoftheirexcellentperformancesastheactivematerialsofnegatives .Ithasbeenshownthatnonstoichiometrichydrogenabsorbingalloyshavethegreatratecapability ,andthecyclinglifeisim provedbythepartialsubstitutionofSnforNiinLaNi5[1～ 3] .Inordertoobtainspecialhydrogenab sorbingalloyswithhighratecapabilityandrelativelowprice ,someAB5nonstoichiometrichydrogenabsorbingalloysareexplored ,whichisbasedonthes…